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Stability of Soil Aggregates in Relation to Organic Constituents and Soil Water Content
Abstract
The effects of soil organic matter content, soil water content and duration of wet-sieving on aggregate stability of soils with contrasting cropping histories were investigated. Long-term pasture samples had a greater aggregate stability than long-term arable samples. However, air-drying aggregates before wet-sieving increased the aggregate stability of long-term pasture samples, but decreased that of long-term arable samples. With increasing duration of wet-sieving, the proportion of water-stable aggregates declined until a near-constant value was reached for each sample. Thus, within a sample there are aggregates possessing a wide range of stabilities; with increasing time under arable cropping there is an increase in the proportion of unstable aggregates present, and the measured aggregate stability, therefore, declines. Unstable aggregates (defined as those dispersed after wet-sieving for 1 min) generally had lower organic matter content than stable ones (those still intact after sieving for 15 min).
The aggregate stability of a regrassed site (13 years of arable plus 2 years of pasture) was markedly higher than that of a corresponding site from 15 years of arable cropping. Nonetheless, levels of organic matter (organic C, total N and hydrolysable carbohydrate) were almost identical at the two sites. However, aggregates from the regrassed site did have a higher biomass C and water-extractable carbohydrate content than those from the 15-year arable site. For a group of soils with varying cropping histories, aggregate stability was significantly more closely correlated with hot water-extractable carbohydrate content than with organic C or hydrolysable carbohydrate content. It is suggested that the hot water-extractable carbohydrate fraction may represent a pool of carbohydrate involved in the formation of stable aggregates.
... Stable soil aggregates also improve soil biological activity and crops productivity by facilitating the movement of air and water (Amézketa, 1999;Karami et al., 2012;Gyawali and Stewart, 2019). The stability of soil aggregates depends strongly on the amount and the composition of organic matter in the soil (Tisdall and Oades, 1982;Chaney and Swift, 1984;Haynes and Swift, 1990) and the content of clay particles and their complexes with humus (Six et al., 2002). Larger aggregates are generally found to be more fragile than small aggregates (Dexter, 1988;Sparling et al., 1994;Six et al., 2004;An et al., 2010;Gyawali and Stewart, 2019). ...
... Soil aggregates are often classified into microaggregates and macroaggregates according to their size, with a threshold diameter of 0.25 mm used for the division into two groups (Tisdall and Oades, 1982;Amezketa et al., 2003;Fristensky and Grismer, 2008). Most studies on the stability of wet aggregates have focused primarily on the stability of macroaggregates, as larger aggregates usually have the greatest impact on the soil structure (Robinson and Page, 1951;Kemper and Rosenau, 1986;Haynes and Swift, 1990;Almajmaie et al., 2017). ...
... Kemper and Rosenau, (1986) suggest leaving the soil in a thin layer with good air circulation for 24 h. (Haynes and Swift, 1990) used a drying oven set at 22 • C for 48 h, (Almajmaie et al., 2017) dried the sample at 40 • C for 24 h, and (Utomo and Dexter, 1982) left the aggregates exposed at the room temperature and humidity for 10 days. The duration of the drying process has a significant impact on the stability of the aggregates. ...
This study introduced and optimized the Sonication and Laser Diffractometry technique (SLD) for evaluating the stability of soil aggregates, drawing comparisons with the conventional Wet Sieving (WS) method. The SLD technique uses ultrasound and particle motion, and is shown to be suitable for fine soils where the WS method struggles with problems such as sieve screen clogging. Results show that the water aggregates stability index (WSAi) determined using SLD is consistent with values obtained from WS and has good reproducibility. Comparisons show that SLD offers advantages in speed, simplicity, and lower potential for human error, providing results in only a few minutes compared to the days required for WS. Challenges such as the adaptability of the methodology to different soil types and equipment remain areas for further research. Nevertheless, this study highlights the potential of SLD as an efficient and reliable method for assessing aggregate stability in soils.
... WSC is a labile soil organic carbon component and is strongly linked to microbial biomass of soil and micro aggregation (Haynes & Swift, 1990;Puget et al., 1998;Ghani et al., 2000). WSC accumulate in soil based on different properties such as weather, topography, slope, management practices and availability of different species of flora and fauna (Ghani et al., 2000). ...
Purpose
Changes in land use have an impact on ecosystem services by affecting soil quality. Thus, soil quality assessment using the soil quality index (SQI) can help better understand the LUC (land use change) impact on soil health.
Methods
This study was established to explore the soil quality of the Nilgiri Hill Region (NHR) in the Western Ghats global biodiversity hotspot (India’s first biosphere reserve) under six major ecosystems {cropland (CL), deciduous forest (DF), evergreen forest (EF), forest plantation (FP), scrubland (SL) and tea plantation (TP)}. The minimum data sets (MDS) were selected using PCA (Principal component analysis) and EO (Experts’ opinion).
Results
LUC from the natural ecosystem has significantly decreased soil quality. The selected indicators under PCA (water-soluble carbohydrates, microbial biomass carbon, dehydrogenase, available K, available N and carbon stock), and EO ( aggregate stability, pH, CEC, available N, available Zn, passive pools, CO2, dehydrogenase, and aggregate size organic carbon (2 mm)) spotlights the wide variation between the natural and the altered ecosystems. Furthermore, the selected indicators were positively correlated with total organic carbon (TOC).
Conclusion
This research cautions that the LUC will have a substantial effect on soil quality, a crucial factor for achieving a future that is environmentally sustainable. Our research indicates the need for an immediate implementation of management strategies to improve the soil quality in degraded ecosystems (CL and TP) of NHR.
... Long-term addition of organic amendments to surface soils can enhance water-holding and infiltration capacities (Haynes and Swift, 1990). The P losses through runoff did not significantly differ between soils with high and low organic matter contents, primarily due to the lower water runoff volume from manure-amended high P soils . ...
Phosphorus dynamics, and biogeochemical processes for unlocking soil phosphorus reserves
... Moreover, the microbial production of EPS has been shown to be enhanced under perennial crop cultivation (Sher et al., 2020). Additionally, our experiment was carried out on silt loam soils with relatively high organic matter, which offer positive conditions for aggregate formation (Haynes & Swift, 1990;Tiemann & Grandy, 2015;Tisdall & Oades, 1982). Perhaps these factors moderated the effects of tillage on the deterioration of aggregate stability. ...
Introduction
Mechanical termination of crops can negatively affect soil biological, chemical, and structural characteristics. Perennial crops do not require annual termination and can improve these same soil characteristics, which has catalysed interest in the development of new perennial crops. Advanced lines of the perennial grass intermediate wheatgrass ( Thinopyrum intermedium [Host] Barkworth and Dewey; IWG) have been bred for increased seed size and marketed as Kernza® perennial grain, but little is known about how this new crop can be terminated for subsequent annual crop production in rotations that enhance agricultural productivity and environmental sustainability.
Materials and Methods
Five methods of terminating IWG were tested in Minnesota, USA. Treatments included mechanical tillage using a chisel plow (CHI), undercutter (UND), and disc (DSC), along with no‐till treatments of glyphosate (GLY) and a repeated‐mowing control (CTRL). Treatment effects on IWG mortality, soil carbon dioxide (CO 2 ) emissions, bulk density, aggregate stability, soil carbon stocks and soybean yield were measured.
Results
Daily CO 2 fluxes differed by treatment ( p < 0.05) on only one of 19 sample dates, and cumulative soil CO 2 emissions over the course of the growing season did not differ across treatments. Bulk density decreased relative to baseline in all treatments except CTRL. Aggregate stability remained unchanged in all treatments except CTRL, which increased from the baseline. Soil carbon stocks did not change in any treatment. Soybean yield was highest in GLY but was not significantly different from CHI or UND.
Conclusions
Soil structure, soil carbon stocks and soil CO 2 emissions were unaffected by tillage and no‐till IWG termination treatments. However, tillage followed by preplanting harrowing proved ineffective at terminating IWG and required subsequent summer herbicide applications. Therefore, additional tillage events may be required to fully terminate IWG when herbicide use is prohibited.
... The field-moist soil samples were air-dried, crushed and sieved (2 mm and 0.2 mm diameter) for laboratory analysis. Soil water content (SWC) was determined gravimetrically using a sterilizer (MOV-212S, Sanyo, Japan) at 105 • C with air circulation (Haynes and Swift, 1990). The soil pH was measured from a soil water suspension (1:2.5 w/v) with a digital pH meter (PB-21, Sartorius, Germany) (Moody et al., 1997). ...
... The aperture diameters of the sieve were 0.053 mm, 0.25 mm, and 2 mm, respectively (Bach and Hofmockel 2014). After 5 min of soaking, the apparatus was operated at a frequency of 50 oscillations min −1 for 15 min (Haynes and Swift 1990) to separate the fractions of silt and clay (SCA, < 0.053 mm), microaggregates (MIA, 0.053-0.25 mm), small macroaggregates (SMA, 0.25-2 mm), and large macroaggregates (LMA, > 2 mm) according to the size of sieve aperture. The proportions of above particle sizes were calculated, and SOC and TN in different particle sizes were analyzed. ...
Purpose
Soil aggregates regulate soil water and temperature, soil fertilizer, and leaf gas exchange. In desert steppes, precipitation restricts the growth and development of plants, and it affects the availability of soil carbon and nitrogen, thereby influencing soil aggregate stability. However, studies on precipitation influence on the stability of aggregates are limited.
Materials and methods
Here, we conducted a 2-year field experiment in a desert steppe of Siziwang Banner, Inner Mongolia, to test the effect of a changing precipitation gradient “reducing precipitation by 50% (W-50%), natural precipitation (W), increasing precipitation by 50% (W+50%), and increasing precipitation by 100% (W+100%)” on the depth distribution, stability of soil aggregates and aggregate-associated organic carbon content (OC), and total nitrogen (TN) contents. We used a wet sieving method yielding silt and clay (SCA, < 0.053 mm), microaggregates (MIA, 0.053–0.25 mm), small macroaggregates (SMA, 0.25–2 mm), and large macroaggregates (LMA, > 2 mm).
Results and discussion
Our results indicated that the topsoil (0–30 cm) was dominated by SCA and MIA. Increasing precipitation increased soil aggregate stability and reduced soil erodibility by increasing water-stable aggregates (WSA, > 0.25 mm). In this study, the comprehensive soil aggregate stability score was the highest at W+100%. Although LMA serve as the main carriers of SOC and TN, MIA-associated OC and TN had the highest contribution rate to SOC and TN. This study revealed that bulk soil properties including MBN, BD, MBC, and pH significantly influenced aggregate stability. Additionally, WSA-associated OC were found to be the most crucial contributors to soil aggregate stability.
Conclusions
Overall, our study indicates that increasing precipitation is beneficial to WSA accumulation and highlighted the vital role of microbial biomass and WSA-associated OC on maintaining soil aggregate stability under precipitation change.
... In general, SOM increases aggregate stability by lowering wetting and increasing cohesion. SOM may partially impart repellency to soil aggregates, contributing to their stability [64] . Chenu et al. [32] reported that after fast wetting of humic soils in southwest France, most of the initial aggregates remained in millimetric size classes for low organic C contents. ...
In arid regions around the world, erosion is a frequent occurrence due to low annual rainfall weakening plants, which in turn affects the concentration of soil organic matter (SOM). When the soil is exposed, sudden and heavy rainfall can lead to soil degradation, particularly in soil with high sodicity where unstable aggregates are easily ruptured, initiating the first phase of soil erosion. To investigate this phenomenon, soil samples were collected from an erosion‐prone area near Maharloo Salt Lake, specifically Chah‐angiri (soil 1) and Kamal-abad (soil 2), which are loam and silty clay loam soils with low SOM. To evaluate the effect of organic matter sources on soil stability, cow manure (animal source) and wheat straw (plant source) were applied to both soil samples at four different rates (0.0, 10.0, 20.0, and 40.0 g kg<sup>−1</sup>) and incubated for four months. The soil’s aggregate stability and mechanical resistance were then assessed using two different methods: mechanical resistance, which was measured as the module of rupture and penetration resistance, and aggregate stability, which was evaluated using the conventional and Le Bissonnais methods. The application of organic matter resulted in a linear increase in aggregate stability in both soils, with the increase in Chah‐angiri (with lower sodicity) being greater than Kamal‐abad (with higher ESP). Both linear and exponential equations showed that organic matter treatment reduced soil mechanical resistance exponentially, with wheat straw proving more effective than cow dung at stabilizing aggregates against slaking and lowering soil mechanical resistance in both soils. Furthermore, the stability of aggregates changed by mechanical breakdown (MWD<sub>stir</sub>) was found to have the strongest relationship among three Le Bissonnais treatments (MWD<sub>slow</sub>, MWD<sub>fast</sub>, and MWD<sub>stir</sub>) and the aggregate stability test using the usual technique (Kemper and Rosenau). The organic matter rate had a significant effect ( P < 0.001) on MWD<sub>stir</sub>, which increased with rate in a linear relationship ( r <sup>2</sup> = 0.957, P = 0.022). Finally, the stability of soil aggregates in water was also investigated.
... In general, SOM increases aggregate stability by lowering wetting and increasing cohesion. SOM may partially impart repellency to soil aggregates, contributing to their stability [64] . Chenu et al. [32] reported that after fast wetting of humic soils in southwest France, most of the initial aggregates remained in millimetric size classes for low organic C contents. ...
In arid regions around the world, erosion is a frequent occurrence due to low annual rainfall weakening plants, which in turn affects the concentration of soil organic matter (SOM). When the soil is exposed, sudden and heavy rainfall can lead to soil degradation, particularly in soil with high sodicity where unstable aggregates are easily ruptured, initiating the first phase of soil erosion. To investigate this phenomenon, soil samples were collected from an erosion-prone area near Maharloo Salt Lake, specifically Chah-angiri (soil 1) and Kamal-abad (soil 2), which are loam and silty clay loam soils with low SOM. To evaluate the effect of organic matter sources on soil stability, cow manure (animal source) and wheat straw (plant source) were applied to both soil samples at four different rates (0.0, 10.0, 20.0, and 40.0 g kg −1) and incubated for four months. The soil's aggregate stability and mechanical resistance were then assessed using two different methods: mechanical resistance, which was measured as the module of rupture and penetration resistance, and aggregate stability, which was evaluated using the conventional and Le Bissonnais methods. The application of organic matter resulted in a linear increase in aggregate stability in both soils, with the increase in Chah-angiri (with lower sodicity) being greater than Kamal-abad (with higher ESP). Both linear and exponential equations showed that organic matter treatment reduced soil mechanical resistance exponentially, with wheat straw proving more effective than cow dung at stabilizing aggregates against slaking and lowering soil mechanical resistance in both soils. Furthermore, the stability of aggregates changed by mechanical breakdown (MWDstir) was found to have the strongest relationship among three Le Bissonnais treatments (MWDslow, MWDfast, and MWDstir) and the aggregate stability test using the usual technique (Kemper and Rosenau). The organic matter rate had a significant effect (P < 0.001) on MWDstir, which increased with rate in a linear relationship (r 2 = 0.957, P = 0.022). Finally, the stability of soil aggregates in water was also investigated.
... NT practices are shown to increase organic matter enrichment in water-extractable carbohydrates (Angers et al., 1993) and higher concentration of WEOC leads to more favorable aggregate stability in soils (Ciric et al., 2016). A previous study found that HWC was more closely correlated with wet aggregate stability compared to SOC (Haynes & Swift, 1990). Reduced disturbance through NT practices promotes residue retention, which helps stabilize soil aggregates and promote greater aggregate stability (Nunes et al., 2020;Weidhuner et al., 2021). ...
Deep soil health (>30 cm) supports deep roots in dryland wheat cropping systems. However, few studies examine how tillage and climate impact soil health indicators deeper than 30 cm in dryland wheat systems. We evaluated how select soil chemical (i.e., nutrients and pH), biological (i.e., carbon [C] and nitrogen [N] fractions and ratios), and physical (i.e., mean weight diameter [MWD] of soil aggregates) health indicators were impacted by depth, tillage, and climate. We sampled soil profiles of the Palouse soil series from 0‐ to 85 cm in depth at three no‐till (NT) and three conventional till (CT) sites across a mean annual precipitation (MAP) gradient (460–660 mm) in the Palouse River watershed. NT sites, compared to CT sites, had higher total C (TC) and N (TN), permanganate oxidizable C, hot‐water extractable C and N, and cold‐water extractable N (0–5 cm); greater soil moisture (0–29 cm); larger MWD (0–5 cm; 10–85 cm); but lower soil pH (0–10 cm; 59–85 cm); less TC, TN, and NO3⁻ (29–85 cm); less NH4⁺ and mineralizable soil C (MINC) (29–59 cm); and lower autoclaved‐citrate extractable (ACE) protein (0–5 cm; 29–85 cm). Sites with higher MAP had greater soil moisture (0–29 cm), higher MINC (0–85 cm), lower CWC (5–10 cm; 29–59 cm), and lower TC and ACE protein (29–85 cm). The variable effects of tillage and climate on these soil health indicators with soil depth show the importance of evaluating soil health in both surface and subsurface soil depths in dryland wheat cropping systems.
... The organic carbon present in the soil sample is analyzed by the wet chromic acid digestion method (Walkley and Black, 1934). Water-soluble and oxidizable carbon was estimated by the methods given by Haynes and Swift (1990) and Blair et al. (1995), respectively. Biomass carbon is determined by the modified fumigation-incubation technique. ...
Improving soil organic carbon by biochar application is of concern in flooded rice soils. However, the effect of biochar on soil physico-chemical and biological properties under increasing levels of CO2 is limited and needs investigation. The present study examined the response of soil carbon pool, and soil enzyme activities of rice upon application of biochar under elevated carbon dioxide (eCO2) - 55030 μmol.mol−1 level. The study was carried out in open-top chambers (OTC) under a rice-rice (Oryza sativa L.) cropping system in 2020. A set of OTCs at ambient CO2 (415 ± 10 μmol mol−1 (aCO2)) served as a check with and without biochar application. The fourth OTC maintained eCO2 without the application of biochar. Rhizosphere soil samples from three critical crop stages viz., active tillering, flowering, and maturity were analyzed for various physico- chemical and biological properties. Most soil biological parameters, specifically soil enzymes, β – glucosidase, urease, and phosphatases, exhibited significant changes during the flowering stage in biochar applied e(CO2) treatment. The per cent increase of 46.8 %, 30.2 %, 18.75 %, and 51.2 % over ambient CO2 in soil organic carbon (SOC), soil microbial biomass carbon (SMBC), oxidizable carbon (OC), and water-soluble carbon, respectively, was observed. This study emphasized that biochar can improve the soil C pool and enzyme activities under anticipated climate change
... The water-soluble carbohydrate carbon (WSC) content is determined by [34]. The ninhydrin reactive nitrogen (NRN) in 20-g soil samples was extracted with 0.5 M potassium sulfate (K 2 SO 4 ) and estimated colorimetrically after mixing the soil extracts with ninhydrin [35]. ...
Effective nitrogen management practices by using two cultivation techniques can improve corn productivity and soil carbon components such as soil carbon storage, microbial biomass carbon (MBC), carbon management index (CMI), and water-soluble carbon (WSC). It is essential to ensure the long-term protection of dry-land agricultural systems. However, excessive application of nitrogen fertilizer reduces the efficiency of nitrogen use and also leads to increased greenhouse gas emissions from farming soil and several other ecological problems. Therefore, we conducted field trials under two planting methods during 2019–2020: P: plastic mulching ridges; F: traditional flat planting with nitrogen management practices, i.e., 0: no nitrogen fertilizer; FN: a common nitrogen fertilizer rate for farmers of 290 kg ha−1; ON: optimal nitrogen application rate of 230 kg ha−1; ON75%+DCD: 25% reduction in optimal nitrogen fertilizer rate + dicyandiamide; ON75%+NC: 25% reduction in optimal nitrogen rate + nano-carbon. The results showed that compared to other treatments, the PON75%+DCD treatment significantly increased soil water storage, water use efficiency (WUE), and nitrogen use efficiency (NUE) because total evapotranspiration (ET) and GHG were reduced. Under the PON75%+DCD or PON75%+NC, the soil carbon storage significantly (50% or 47%) increased. The PON75%+DCD treatment is more effective in improving MBC, CMI, and WSC, although it increases gaseous carbon emissions more than all other treatments. Compared with FFN, under the PON75%+DCD treatment, the overall CH4, N2O, and CO2 emissions are all reduced. Under the PON75%+DCD treatment, the area scale GWP (52.7%), yield scale GWP (90.3%), biomass yield (22.7%), WUE (42.6%), NUE (80.0%), and grain yield (32.1%) significantly increased compared with FFN, which might offset the negative ecological impacts connected with climate change. The PON75%+DCD treatment can have obvious benefits in terms of increasing yield and reducing emissions. It can be recommended to ensure future food security and optimal planting and nitrogen management practices in response to climate change.
... The initial soil moisture content influences the adhesion forces between soil aggregates, which affects not only soil porosity but also aggregate water stability (Haynes and Swift, 1990;Dagesse, 2013). Vermang et al. (2009) studied silt loam soil in Belgium, and the results showed that the stability of soil aggregates gradually increased with an increase in initial moisture content within a certain range. ...
Soil aggregate stability is a key factor that affects soil erosion and ecological restoration. In this study, three typical plinthosol profiles in Wuhan (W), Yueyang (Y), and Jiujiang (J) were selected, and the mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension were used as indicators of soil aggregate stability, as well as the erodibility factor (K value). Based on the end-member analysis, it appears that the plinthosols in the three profiles were wind-formed deposits, which greatly affected particle size and erodibility. There was a greater resistance to erosion among the plinthosols developed from finer grains than among those developed from coarse grains. The stability of aggregates in profiles W and Y decreased gradually with depth, while it varied little in profile J. The initial moisture content had a significant effect on the anti-erodibility of the plinthosols, and there were some differences between the profiles: in profile W, the anti-erodibility increased with the increase in initial moisture and reached its maximum value at the initial moisture content of 20%; in profiles Y and J, when the initial moisture content was 15%, the anti-erodibility was the highest. Reddish matrix had a higher anti-erodibility than white veins. Profile J had the largest stability gap between white veins and reddish matrix, followed by profile Y and W. These results provide a theoretical basis for the conservation of soil and water in the Yangtze River middle reaches by revealing the stability characteristics of plinthosols.
... Traditionally, crop water status is mainly determined by soil moisture status. Based on the relevant theories of soil physics, many methods, including the drying method, electrical resistance method, neutron scattering method, time-domain reflectometer method, etc., have been developed to measure the soil water content [3][4][5] . These methods can be easily performed in small-scale areas to get high-precision results. ...
Large area of soil moisture status diagnosis based on plant canopy spectral data remains one of the hot spots of agricultural irrigation. However, the existing soil water prediction model constructed by the spectral parameters without considering the plant growth process will inevitably increase the prediction errors. This study carried out research on the correlations among spectral parameters of the canopy of winter wheat, crop growth process, and soil water content, and finally constructed the soil water content prediction model with the growth days parameter. The results showed that the plant water content of winter wheat tended to decrease during the whole growth period. The plant water content had the best correlations with the soil water content of the 0-50 cm soil layer. At different growth stages, even if the soil water content was the same, the plant water content and characteristic spectral reflectance were also different. Therefore, the crop growing days parameter was added to the model established by the relationships between characteristic spectral parameters and soil water content to increase the prediction accuracy. It is found that the determination coefficient (R 2) of the models built during the whole growth period was greatly increased, ranging from 0.54 to 0.60. Then, the model built by OSAVI (Optimized Soil Adjusted Vegetation Index) and Rg/Rr, two of the highest precision characteristic spectral parameters, were selected for model validation. The correlation between OSAVI and soil water content, Rg/Rr, and soil water content were still significant (p<0.05). The R 2 , MAE, and RMSE validation models were 0.53 and 0.58, 3.19 and 2.97, 4.76 and 4.41, respectively, which was accurate enough to be applied in a large-area field. Furthermore, the upper and lower irrigation limit of OSAVI and Rg/Rr were put forward. The research results could guide the agricultural production of winter wheat in northern China. Establishment of soil moisture model based on hyperspectral data and growth parameters of winter wheat. Int J Agric & Biol Eng, 2023; 16(3): 1-8.
... For assessment of soil physical quality, the distribution, as well as stability of soil aggregates, are considered essential, emphasizing the importance of soil management on particle aggregation and disaggregation (Silva et al., 2014). The aggregate stability is generally strongly correlated with SOC content by playing a vital role as the organic polymer binding agents (Haynes & Swift, 1990;Majumder et al., 2010) and the physical trapping of particles by fine roots and fungal hyphae (Helfrich et al.,2015) which promote aggregate cohesion. Additionally, fertilization and irrigation practices that boost crop productivity, biomass, and root production may indirectly enhance the system's carbon inputs and contributes to the aggregate formation (Yadav et al., 2017). ...
The study was undertaken by utilizing an ongoing long-term experiment on continuous cropping at Anand Agricultural University that began in 1980. From 1994 onwards, a modification was made by including Farmyard Manure (FYM) treatments for studying the following objectives: long-term effect of fertility levels with and without FYM on changes in soil organic carbon pools for assessing the role of organics and chemical fertilizers on soil organic carbon buildup and their interrelationship with soil aggregate stability under the pearl millet-mustard-cowpea (F) cropping sequence. Under F1 (FYM @ 10 t/ha) and FL3 (NP application @150 percent of RDF), there was a considerable improvement in the status of Walkley and Black C (WBC), Soil Microbial Biomass Carbon (SMBC), and Total Organic Carbon (TOC) compared to the control in both depths (0-15 and 15-30 cm). Long-term manuring and fertilization practices affect aggregate development and stabilization. In all depths, the highest soil macroaggregates and microaggregates were found when FYM @ 10 t/ha and FL3 (150 percent NP) were applied. Under FYM treated plots and with the greater dose of NP (NP application @150 percent of RDF) in both the surface and sub-surface layers, the maximum water-stable aggregate expressed as mean weight diameter (MWD) was recorded. Furthermore, a significantly positive correlation was observed between SMBC and enzymatic activities (phosphatase, urease, and dehydrogenase) in both the soil depths; indicating the effect of labile C on the biological activities of soil which might be achieved by means of changes in microbial diversity of the soil.
... These results agree with H3 that proposed the PPT event size and previous conditions of the semiarid grassland would control the magnitude of the priming NEE effect. The previous VWC offers insight into the potential dry-wet shock experienced by soil aggregates and microorganisms (Haynes and Swift, 1990) and thus accounts for nutrient and labile C accumulation in soil (Bailey et al., 2019). ...
Infrequent and small precipitation (PPT) events characterize PPT patterns in semiarid grasslands; however, plants and soil microorganisms are adapted to use the unpredictable small pulses of water. Several studies have shown short-term responses of carbon and nitrogen mineralization rates (called the "priming effect" or the Birch effect) stimulated by wet-dry cycles; however, dynamics, drivers, and the contribution of the priming effect to the annual C balance are poorly understood. Thus, we analyzed 6 years of continuous net ecosystem exchange measurements to evaluate the effect of the PPT periodicity and magnitude of individual PPT events on the daily/annual net ecosystem C exchange (NEE) in a semiarid grassland. We included the period between PPT events, previous daytime NEE rate, and previous soil moisture content as the main drivers of the priming effect. Ecosystem respiration (ER) responded within a few hours following a PPT event, whereas it took 5-9 d for gross ecosystem exchange (GEE; where −NEE = GEE + ER) to respond. Precipitation events as low as 0.25 mm increased ER, but cumulative PPT > 40 mm infiltrating deep into the soil profile stimulated GEE. Overall, ER fluxes following PPT events were related to the change in soil water content at shallow depth and previous soil conditions (e.g., previous NEE rate, previous soil water content) and the size of the stimulus (e.g., PPT event size). Carbon effluxes from the priming effect accounted for less than 5 % of ecosystem respiration but were significantly high with respect to the carbon balance. In the long term, changes in PPT regimes to more intense and less frequent PPT events, as expected due to the effects of climate change, could convert the semiarid grassland from a small C sink to a C source.
... Six et al. [53], revealed that macro aggregates comprised of micro aggregates as well as organic binding agents due to which the OC increased in macro aggregates as compared to micro aggregates. Others studies are also present that shows a strong correlation between SOC and aggregates stability, as aggregates are more cohesive due to organic polymer binding agents [54,55]. However, there are also studies which revealed that organic fertilizers may not influence micro aggregates and remained similar to unfertilised (control) [56,57]. ...
Soil aggregation in forest ecosystem is considered as a significant physical process mainly influenced by manure, fertilizers or combination. This aggregation may directly alter the soil nutrient and their fractions in soil. So, soil samples were collected from two types of forests i.e. Natural Korean pine forests (NKPF) and Korean pine plantation (KPP) in order to know the quantities of organic and inorganic Phosphorus (P) amounts in different aggregate sizes viz. >5 mm, 2-5 mm, 0.25-2 mm, <0.25 mm under forest litter and synthetic fertilizer application below the treatments as undisturbed soil (CK), removed litter (RL), altered litter (AL) while the fertilizer treatments were as control; C: (No added N and P,), L: low (5 g N m − 2 a − 1 + 5 g P m − 2 a − 1), M: medium (15 g N m − 2 a − 1 + 10 g P m − 2 a − 1) and H: high concentration (30 g N m − 2 a − 1 + 20 g P m − 2 a − 1), respectively. The results showed that H 2 O-Pi, NaHCO 3-Pi, Residual Pi, SOC were highest retained in larger soil aggregates (>5 mm) and decreased with the decreasing aggregate size, while other variables, i.e., NaOH-Pi, NaHCO 3-Po, pH and T-N were not affected in aggregate size. H 2 O-Pi (48 ppm), NaHCO 3-Pi (68 ppm), NaHCO 3-Po (80 ppm), NaOH-Po (623 ppm), HCL-Po (67 ppm), SOC (20.36 ± 1.6) was estimated in medium fertilizer treatment. PCA analysis showed that spread/variance of data points on F1 (62.90%) is more than spread/variance of data points on F2 (57.74%) in NKPF and KPP, respectively, while correlation matrix showed high correlation between H 2 O-Pi and NaOH-Pi (0.63) and H 2 O-Pi and NaHCO 3-Pi (0.63) while a strong negative correlation was present between Res-Pi and Po (− 0.61). Moreover, litter inputs increased the organic-P fractions in soil particularly at medium treatment.
... SOC originates from plants, animals, and microorganisms and their exudates. Since 1948 [14], it has been known that the SOC increases the soil stability, defined by Haynes and Swift [15] as the capacity to resist the slacking and the dispersive actions of water in order to maintain the soil's porous structure intact. According to the hierarchical theory of aggregation, the soil is composed of macroaggregates that are made of more stable microaggregates of primary particles [16]. ...
A soil depleted of its organic carbon content is typically destabilized, i.e., its capacity to maintain its microstructure intact under various stress conditions weakens, and consequently, landslides and mudflows can be triggered and propagated more easily. In a previous work, we showed with a rheological analysis that the removal of the sole water-soluble organic carbon “destabilized” the slurry very similarly to what occurs with the removal of the vast majority of soil organic carbon. In principle, the water-soluble organic carbon can be dissolved by rainfall, during which water can infiltrate the soil, eventually leaving it either by percolation or evaporation. These two processes are mimicked here with two different soil water wetting procedures. The stability of the treated (wetted) soils is studied with rheological and granulometric experiments. The former run on concentrated suspensions, while the latter run on very diluted ones. Despite this, the results agreed very well, indicating that the two wetting procedures induce the same destabilization of the soil which behaves as the one depleted by the whole water-soluble organic carbon. Our results concluded that a soil destabilized by a wetting procedure, i.e., by a rainfall event, will be more prone to trigger a landslide that will propagate more swiftly and will stop with more difficulties.
... concern saturated hydraulic conductivity, aggregate stability (Bettoni et al., 2022;Cantón et al., 2009;Cerdà, 1998), and soil water repellence (Doerr et al., 2003;Lemmnitz et al., 2008;Miyata et al., 2007). Aggregate stability is strongly influenced by the amount of soil organic carbon (SOC) (Haynes and Swift, 1990; Le Bissonnais and Arrouays, 1997;Smith et al., 2015), which is often higher under forest vegetation, where a low biodegradability of soil organic matter (SOM) favours the accumulation of SOC (Guo and Gifford, 2002). However, under agricultural use, SOC is generally lower due to regular tillage and biomass harvesting (Guo and Gifford, 2002;Rehfuess, 1990;Vogel and Conedera, 2020). ...
In mountain regions, soil landscapes are highly vulnerable against soil loss. Moreover, these environments are
particularly affected by land use changes, which influence soil properties and related processes like surface
runoff generation and soil erosion. These processes are in turn amplified by extreme climatic events and intensive
geomorphological dynamics. The objective of this study is to quantitatively assess the effects of land use changes
on surface runoff and soil erosion in a southern Alpine valley (Onsernone valley, Switzerland) characterized by a
former intense land use followed by a progressive abandonment in the last decades. Surface runoff and related
sediment transport has been analysed under controlled and reproducible conditions using a portable rainfall
simulator device (1 m2
). The results show a statistically significant increase in surface runoff when the soil gets
water repellent reducing the surface infiltration capacity and generating preferential flow paths, which prevent a
homogeneous wetting of the soil. However, the documented high sensitivity of surface runoff to land use changes
does not result in an equally high sensitivity to soil erosion processes. Instead, soils display a high aggregate
stability leading to very low sediment transports except for abandoned and reforested agricultural terraces.
There, the lack of maintenance and progressive collapse of terrace dry walls locally increase slope angles and
directly exposes the soil to atmospheric agents and surface runoff, which causes soil erosion rates beyond the
customary natural level.
... For instance, hot-water soluble carbohydrates (HWSC), as an important pool of labile carbon including plant and microbial carbohydrates, can be used as a soil quality indicator in soil-plant ecosystems (Ghani et al., 2003). Over the years, extensive research into HWSC has shown that it is more closely related to soil aggregation and structural stability than total carbohydrates or SOC across a range of soil types (Haynes and Swift, 1990;Degens, 1997;Debosz et al., 2002;Guo et al., 2019). In addition, Duval et al. (2018) reported that among the SOC labile fractions, the fine particulate organic carbon and HWSC were the most sensitive indicators of soil quality in agricultural lands. ...
... Roots and soils are considered key components for adaptation of crops since they impact the availability of water and minerals. The properties of structural units of soil determine overall soil physical and mechanical properties such as retention and movement of water, aeration, and temperature that have direct impacts on plant growth, and this in turn is strongly influenced by carbon content of soil (Haynes and Swift, 1990). Plants are known to exude ~11% of net photosynthetically fixed carbon and 10-16% of total plant nitrogen as rhizodeposits via roots into the rhizospheric region (Jones et al., 2009). ...
Arid and semi-arid regions are vast reservoirs of hardy organisms, including plant species and the associated microorganisms. An important crop of these regions is the pearl millet which serves as a source of food and feed, especially in the rainfed tracts. The inherent hardiness of the crop has attracted researchers from all over the world to unveil its underlying biology as well as to assess the role of associated microflora in imparting the hardiness that allow pearl millet to survive under very harsh climatic conditions. The pearl millet-associated microbiome consists of the rhizospheric (within the rhizosphere), phyllospheric (on the leaf surfaces) and endophytic (within the internal tissues) microbial communities. These microorganisms play a critical role in plant health and growth by improving the uptake of essential nutrients, protecting plants from pathogens, and enhancing drought and disease tolerance. This has been demonstrated in several studies wherein microbial inoculation of pearl millet resulted in increased protection from diseases like downy mildew, enhanced drought and high temperature tolerance and improved plant characteristics including yield. Exploring native stress tolerant and plant growth promoting microorganisms and unraveling their effect on molecular biology and biochemistry of pearl millet plants holds huge potential for their utilization in sustainable arid and semi-arid agriculture systems.
... Chloroform fumigation extraction method described by Witt et al. (2000) was used for the analysis of microbial biomass carbon (MBC). For the analysis of other three fractions of carbon, viz., permanganate oxidizable carbon (POXC), water soluble carbohydrate carbon (WSC), and soil oxidizable organic carbon, the methods described by Blair et al. (1995); Haynes and Swift (1990), and Walkley and Black (1934), respectively, were followed. The analysis of microbial population and enzymatic activities was done with field moist soil sample. ...
Introduction
Conventional rice production techniques are less economical and more vulnerable to sustainable utilization of farm resources as well as significantly contributed GHGs to atmosphere.
Methods
In order to assess the best rice production system for coastal areas, six rice production techniques were evaluated, including SRI-AWD (system of rice intensification with alternate wetting and drying (AWD)), DSR-CF (direct seeded rice with continuous flooding (CF)), DSR-AWD (direct seeded rice with AWD), TPR-CF (transplanted rice with CF), TPR-AWD (transplanted rice with AWD), and FPR-CF (farmer practice with CF). The performance of these technologies was assessed using indicators such as rice productivity, energy balance, GWP (global warming potential), soil health indicators, and profitability. Finally, using these indicators, a climate smartness index (CSI) was calculated.
Results and discussion
Rice grown with SRI-AWD method had 54.8 % higher CSI over FPR-CF, and also give 24.5 to 28.3% higher CSI for DSR and TPR as well. There evaluations based on the climate smartness index can provide cleaner and more sustainable rice production and can be used as guiding principle for policy makers.
... The application of K-humate at a high rate caused a significant increase in SOM status, total nitrogen (N), base saturation, soil pH, and CEC (Yilmaz, 2011). The K-humate improved the soil aggregate formation (soil aggregation) due to enhanced flocculation and cementation (organo-mineral complexations) and reduced the soil bulk density (Haynes and Swift, 1990), an indicative of the improved functionality of humic acids (Glaser et al., 2002). Under the presence of 2:1 clay minerals in soil (smectite), humic substances were found to be more efficacious in improving adherence between soil mineral and organic particles, resulting in improved soil structural changes (Yamaguchi et al., 2004). ...
... The application of K-humate at a high rate caused a significant increase in SOM status, total nitrogen (N), base saturation, soil pH, and CEC (Yilmaz, 2011). The K-humate improved the soil aggregate formation (soil aggregation) due to enhanced flocculation and cementation (organo-mineral complexations) and reduced the soil bulk density (Haynes and Swift, 1990), an indicative of the improved functionality of humic acids (Glaser et al., 2002). Under the presence of 2:1 clay minerals in soil (smectite), humic substances were found to be more efficacious in improving adherence between soil mineral and organic particles, resulting in improved soil structural changes (Yamaguchi et al., 2004). ...
Humic materials are categorized into three main classes: humic acids (alkaline soluble), fulvic acids (acid and alkaline soluble), and insoluble humin. The use of humic products is increasing among farmers due to their ability to considerably improve soil health and alter soil characteristics. Besides being used as soil amendments, humic products can also be used to formulate a variety of synthetic and organic fertilizers. Most likely, humic acids appear to improve the cation exchange capacity (CEC) of soil, which may contribute to an improvement in mineral nutrients retention in soil. The term “Alkamides” denotes a group of secondary metabolites consisting of nearly 200 compounds, and all of them have a special structure that results from the condensation of an unsaturated fatty acid and an amine group. The Alkamides (N-iso-propyldecanamide) in the macro-molecular structure of humic acids is linked to hormonal changes, including auxin and nitric oxide, that presumably regulate root growth. The resistance of humic materials to microbial actions helps in maintaining soil structural stability. The humic acids may alter the cellular electrical environment via modulation of the plasma membrane proton pump (PM-ATPase). Intensified proton (H+) extrusion to apoplast and enhanced root growth both reflect an extension in root absorption capacity that modulates the plant nutrition. This chapter illustrates the possible effects of humic acids and Alkamides on root development, nutrients uptake efficiency, nutrients cycling, and crop yield.
... Finally, a negative relationship between WSA, MWD, and SWC may be explained by cohesion forces. When aggregates are dry, their stability is higher [77]. Cohesion forces hold aggregates until SWC increases. ...
Soil and water loss due to traditional intensive types of agricultural management is widespread and unsustainable in Croatian croplands. In order to mitigate the accelerated land degradation, we studied different cropland soil management strategies to obtain feasible and sustainable agro-technical practices. A rainfall simulation experiment was conducted at 58 mm h–1 over 30 min on 10 paired plots (0.785 m2), bare and straw covered (2 t ha−1). The experiment was carried out in maize cultivation (Blagorodovac, Croatia) established on Stagnosols on slopes. Measurements were conducted during April (bare soil, after seeding), May (five-leaves stage), and June (intensive vegetative growth) making 60 rainfall simulations in total. Straw reduced soil and water losses significantly. The highest water, sediment loss, and sediment concentrations were identified in tillage plots during May. Straw addition resulted in delayed ponding (for 7%, 63%, and 50% during April, May and June, respectively) and runoff generation (for 37%, 32%, and 18% during April, May and June, respectively). Compared with the straw-mulched plot, tillage and bare soil increased water loss by 349%. Maize development reduced the difference between bare and straw-mulched plots. During May and June, bare plots increase water loss by 92% and 95%, respectively. The straw mulch reduced raindrop kinetic energy and sediment detachment from 9, 6, and 5 magnitude orders in April, May, and June, respectively. Overall, the straw mulch was revealed to be a highly efficient nature-based solution for soil conservation and maize cultivation protection.
... Water-soluble carbohydrates are components of labile soil organic carbon and are also related to soil microbial biomass and micro-aggregation [59][60][61]. The accumulation of WSC in soil results from a complex set of interactions between the soil matrices, climate, topography, cultivation, and the diversity of fauna and flora. ...
Accelerating land-use change (LUC) in the Nilgiri Hill Region (NHR) has caused its land to
mortify. Although this deterioration has been documented, the destruction of buried gem soil has
not been reported. Therefore, this study was conducted to assess the impact of LUC on soil-carbon
dynamics in the six major ecosystems in the NHR: croplands (CLs), deciduous forests (DFs), evergreen
forests (EFs), forest plantations (FPs), scrublands (SLs), and tea plantations (TPs). Sampling was
conducted at selected sites of each ecosystem at three depth classes (0–15, 15–30, and 30–45 cm) to
quantify the carbon pools (water-soluble carbon, water-soluble carbohydrates, microbial biomass
carbon, microbial biomass nitrogen, dehydrogenase, and different fractions of particulate organic
carbon). We found that the LUC significantly decreased the concentration of carbon in the altered
ecosystems (49.44–78.38%), with the highest being recorded at EF (10.25%) and DF (7.15%). In
addition, the effects of the LUC on the aggregate size of the organic carbon were dissimilar across
all the aggregate sizes. The relatively high inputs of the aboveground plant residues and the richer
fine-root biomass were accountable for the higher concentration of carbon pools in the untouched
EFs and DFs compared to the SLs, FPs, TPs, and CLs. The results of the land-degradation Index (LDI)
depicted the higher vulnerability of TP (−72.67) and CL (−79.00). Thus, our findings highlight the
global importance of LUC to soil quality. Henceforth, the conservation of carbon pools in fragile
ecosystems, such as the NHR, is crucial to keep soils alive and achieve land-degradation neutrality.
... Water-soluble carbohydrates are components of labile soil organic carbon and are also related to soil microbial biomass and micro-aggregation [59][60][61]. The accumulation of WSC in soil results from a complex set of interactions between the soil matrices, climate, topography, cultivation, and the diversity of fauna and flora. ...
Accelerating land-use change (LUC) in the Nilgiri Hill Region (NHR) has caused its land to mortify. Although this deterioration has been documented, the destruction of buried gem soil has not been reported. Therefore, this study was conducted to assess the impact of LUC on soil-carbon dynamics in the six major ecosystems in the NHR: croplands (CLs), deciduous forests (DFs), evergreen forests (EFs), forest plantations (FPs), scrublands (SLs), and tea plantations (TPs). Sampling was conducted at selected sites of each ecosystem at three depth classes (0–15, 15–30, and 30–45 cm) to quantify the carbon pools (water-soluble carbon, water-soluble carbohydrates, microbial biomass carbon, microbial biomass nitrogen, dehydrogenase, and different fractions of particulate organic carbon). We found that the LUC significantly decreased the concentration of carbon in the altered ecosystems (49.44–78.38%), with the highest being recorded at EF (10.25%) and DF (7.15%). In addition, the effects of the LUC on the aggregate size of the organic carbon were dissimilar across all the aggregate sizes. The relatively high inputs of the aboveground plant residues and the richer fine-root biomass were accountable for the higher concentration of carbon pools in the untouched EFs and DFs compared to the SLs, FPs, TPs, and CLs. The results of the land-degradation Index (LDI) depicted the higher vulnerability of TP (−72.67) and CL (−79.00). Thus, our findings highlight the global importance of LUC to soil quality. Henceforth, the conservation of carbon pools in fragile ecosystems, such as the NHR, is crucial to keep soils alive and achieve land-degradation neutrality.
... Also, Georgia et al. (2010) reported an increase in weight of tomato fruit as a result of application olive waste water. According to (Haynes and Swift (1990) and (Noval and Rezk (2009), applying recycling olive oil wastes for the soil improved soil characteristics that led to significant values of fruit quality. Moreover, PGPR strains that produce plant hormones, such as auxins and cytokines, can stimulate plant cell elongation or cell division (Guardiola, 2008). ...
... High resistance and resilience imply low vulnerability. Soil structural quality (e.g., pore network properties and aggregate stability) declines with increase in land use pressures (Haynes and Swift, 1990;Hu et al., 2021;Hu et al., 2018). This affects both resistance and resilience, hence its vulnerability to further degradation. ...
Soil structure affects a range of soil functions (e.g., water, air, heat, and nutrient transport) and ecosystem services (e.g., production, climate regulation). Agricultural intensification is a dominant factor in global soil structural degradation. Understanding the vulnerability of soils to structural degradation may be important to land use planning and identifying management practices that mitigate the risk of degradation. We review the current methods for assessing soil structural vulnerability and the influencing factors, focussing on soil compaction and aggregate breakdown as two key measures of structural degradation. Methods for assessing risk of soil structural degradation and management practices affecting the risk are also discussed. Critical research gaps are identified, including the lack of studies that demonstrate the link between soil structural vulnerability and loss of soil functions or ecosystem services. Our review of the literature identified that the terms susceptibility, vulnerability, and risk are often used interchangeably. We propose definitions that can be used to distinguish these terms. Soil properties (relatively static), soil wetness, and land use stress (e.g., climate and management practices) are progressively included in the assessments of soil structural susceptibility, vulnerability, and risk. Existing indicators for assessing soil structural vulnerability may not be suitable to predict potential effects on ecosystem services. We highlight that soil structural vulnerability assessments should focus on key soil structural indicators (e.g., pore network-based hydraulic properties) affecting soil functions and ecosystem services. Both the state (i.e., condition) of soil structure and its vulnerability should be included for assessing soil structural degradation. To overcome the limitations of previous assessments, we developed a conceptual model linking soil structural vulnerability assessment to loss of soil functions and ecosystem services. Our review provides insights on assessment metrics and frameworks to develop management practices that improve soil structure and delivery of ecosystem services.
... Generally, there was a positive correlation between soil aggregate stability and organic matter (Chenu et al., 2000). Therefore, higher TOC content in the restored wetland was conducive to the stability of the basement soil aggregate (Haynes and Swift, 2010), which made the restored wetland have better buffer capacity. Furthermore, concurrent decreases in bulk density and increases in TOC frequently occurred following wetland restoration (Craft, 2000;Bruland and Richardson, 2005), confirming the good recovery of the restored wetland from the abandoned fish pond in this study. ...
To restore the abandoned fish ponds to "near natural" state, the wetland restoration was carried out in Gonghu Bay lakeside, and its long-term performance of controlling external load was studied for 5 years. The findings showed that water quality and biodiversity had been improved dramatically after the preliminary transformation. The concentrations of permanganate index (CODMn), total nitrogen (TN), and total phosphorus (TP) obviously decreased from 12.91 mg L-1 to 4.32 mg L-1, from 3.46 mg L-1 to 1.42 mg L-1, and from 0.27 mg L-1 to 0.04 mg L-1, respectively. The proportion of Cyanophyta was effectively reduced from 31.82% to 18.89%, and favored the growth of diatoms (31.82%-37.78%) to be the dominant algae species. Aquatic plant species and coverage gradually increased from 16 to 56 and from 5% to 60%, respectively. An in-deep monitoring done for 5 years (2013-2017) showed that the wetland achieved a satisfactory removal efficiency of 58.95% for TN, 64.60% for TP, and up to 77.83% for chlorophyll-a. Besides, three pollution scenarios, such as stormwater runoff, algal bloom, and continuous water transfer, were selected to explore the tolerance of the wetland to the suddenly increased pollution loads. The results dedicated that even if the inlet load was up to 1.0 × 105 m3 d-1, the removal rate coefficients of wetland for chlorophyll-a, TP, and TN were 0.135-0.239 d-1, 0.041-0.112 d-1, and 0.030-0.109 d-1, respectively, which were equivalent to the well-running wetlands. This study confirmed that the wetland was not only a promising ecological remediation technique to contaminated abandoned fish ponds, but also could withstand high pollution load, which had the prospect of sustainable utilization.
... 4) FM improved soil enzyme activity and microbial biomass, which led to the synthesis of microbial polysaccharides. These are closely related to aggregate stability (Haynes and Swift, 1990). Therefore, FM improved soil aggregate stability and reduced soil erosion . ...
Film mulching (FM) is an agronomic measure worldwide, yet its effect on cadmium (Cd) accumulation in plants is unknown. This study investigated the potential for phytoremediation with FM treatment of Cyperus esculentus L. (chufa) and Sedum alfredii Hance (S. alfredii)-oil crop rotation system. The FM increased the biomass and Cd content of the chufa, resulting in an increase of 65.0-193.5% in the Cd accumulation. S. alfredii also was planted using non-film mulching and film mulching (FMSA), followed by rotation oil plants using non-film mulching. Soil pH and dissolved organic carbon content were significantly reduced, and the Cd grain size fraction of macro-aggregates was significantly increased by FMSA, which increased the uptake of available Cd by S. alfredii. This phenomenon further promoted the accumulation of Cd in S. alfredii and reduced the Cd content of aboveground tissues and seeds in subsequent oil crops. Vegetable oils were safely produced in all treatments due to their low Cd content. Compared with non-film mulching, FM increased the Cd accumulation of rotation systems by 66.8-96.4%, and the Cd remediation efficiency reached 11.8-12.9%. Collectively, the FM treatment effectively improved the remediation efficiency of Cd in the rotation system and ensured the safe production of vegetable oil.
... The highest HWEC at the surface soil obtained in Upland Rice (101.4 μg C/g soil) and at the subsurface soil, the highest HWEC was obtained in Terrace Rice (142 μg C/g soil) system. Haynes and Swift (1990) and Haynes et al. (1991) similarly found that hot water-soluble carbohydrates were best correlated with aggregate stability as compared to other fractions in pasture soils. This finding could be referred to the higher content of HWEC in the Upland Rice condition and obtained the highest MWD content in the same land use system. ...
Inappropriate land use system in Meghalaya aggravates to soil erosion and other soil degradation. The land use is an important factor affecting soil organic carbon (SOC) accumulation and storage in soils. The study was conducted at Bhoirymbong of Ri-Bhoi District, Meghalaya in eight (8) different land use systems viz. Jhum, Upland Rice, Terrace Rice, Rice mono-culture, Rice-Potato, Pineapple, Mixed forest and Broom grass. The soil texture, soil organic carbon (SOC), soil microbial biomass carbon (SMBC), Exchangeable Ca+Mg and hot water extractable carbon (HWEC) were measured in soil of different land uses. Aggregates were fractionated using a wet-sieving procedure to obtain the distribution of water-stable aggregates. Mean Weight Diameter (MWD) is found highest in Upland Rice (2 mm) and Terrace Rice (1.72 mm) at 0-10 cm and 10-20 cm depth, respectively in the study area. Furthermore, higher MWD in surface soil was obtained from Upland rice which indicated that as the Upland rice cultivation is traditionally a mono-culture activity without much soil manipulation the aggregation might not have broken in the cultivation process. The pH is moderately acidic in nature ranging in Bhoirymbong (5.26-6.42). Clay content was highest in Pineapple system (0-10cm) and Terrace Rice system (10-20cm) in Bhoirymbong area. In case of MWD, it was the highest in Upland Rice (2 mm) and Terrace Rice (1.72 mm) at 0-10 cm and 10-20 cm depth, respectively in both the study areas. At both depth of Bhoirymbong areas, Exch. Ca++ and Mg++ was found to be highest in Rice monoculture system (3.32 meq/100g soil and 2.68 meq/100g soil). SMBC, Exchangeable Ca++ and Mg++, Clay, HWEC and SOC show significant (p≤0.05) and strong positive correlation with MWD at both depths. The findings from this study had shown the land use system had significant influence on the aggregating elements. Besides, the influence of land use system on aggregating elements varied according to land uses. Hence, the findings of this study clearly shown that the proper selection of land use according to the state of soil aggregating elements for better soil sustainability.
... The highest HWEC at the surface soil obtained in Upland Rice (101.4 μg C/g soil) and at the subsurface soil, the highest HWEC was obtained in Terrace Rice (142 μg C/g soil) system. Haynes and Swift (1990) and Haynes et al. (1991) similarly found that hot water-soluble carbohydrates were best correlated with aggregate stability as compared to other fractions in pasture soils. This finding could be referred to the higher content of HWEC in the Upland Rice condition and obtained the highest MWD content in the same land use system. ...
... Hence, irrespective of the described land use changes in the Onsernone valley, the amount of stable aggregates is very high, pointing to a very low soil erodibility. This can be attributed to the generally high amounts of SOM (Haynes and Swift, 1990;Le Bissonnais and Arrouays, 1997;Smith et al., 2015), so that, regardless of different SOC amounts between the different LCTUs, the critical threshold value of SOC content is not reached that might result in a distinct reduction of aggregate stability. This insensitivity of soil aggregate stability to land use changes in the study area is remarkable, since it was repeatedly used in the past as an indicator for soil's stability and low soil erosion potential (e.g., Ali et al., 2017;Pohl et al., 2009;Fultz et al., 2013). ...
Landscape sensitivity is a concept referring to the likelihood that changes in land use may affect in an irreversible way physical and chemical soil properties of the concerned landscape. The objective of this study is to quantitatively assess the sensitivity of the southern Alpine soil landscape regarding land use change-induced perturbations. Alpine soil landscapes can be considered as particularly sensitive to land use changes because their effects tend to be enhanced by frequent extreme climatic and topographic conditions as well as intense geomorphologic activity. In detail, the following soil key properties for soil vulnerability were analysed: (i) soil texture, (ii) bulk density, (iii) soil organic carbon (SOC), (iv) saturated hydraulic conductivity (Ksat), (v) aggregate stability and (vi) soil water repellency (SWR). The study area is characterized by a steep, east-west oriented valley, strongly anthropized in the last centuries followed by a progressive abandonment. This area is particularly suitable due to constant lithological conditions, extreme topographic and climatic conditions as well as historic land use changes. The analysis of land use change effects on soil properties were performed through a linear mixed model approach due to the nested structure of the data. Our results showa generally high stability of the assessed soils in terms of aggregate stability and noteworthy thick soils. The former is remarkable, since aggregate stability, which is commonly used for detecting land use-induced changes in soil erosion susceptibility, was always comparably high irrespective of land use. The stability of the soils is mainly related to a high amount of soil organic matter favouring the formation of stable soil aggregates, decreasing soil erodibility and hence, reducing soil loss by erosion. However, the most sensitive soil property to land use change was SWR that is partly influenced by the amount of soil organic carbon and probably by the quality and composition of SOM.
... We chose POXC as an indicator of soil carbon dynamics because it is a good proxy for labile C (i.e., readily available to soil microorganisms) and has been reported to be more responsive to soil management than TOC (Culman et al., 2012;Hurisso et al., 2016). We also chose WSA as a sensitive indicator of changes in soil structure due to management (Haynes and Swift, 1990). To those ends, we hypothesized that (1) in the spring following an inversion tillage event, the three soil health indicators would be smaller compared to those for continuous no-till soils; and (2) indicator values would return to similar levels observed in no-till soils after returning to no-till with cover crops and 2 years of perennial crops in the sixth year of the rotation. ...
Maximizing living cover and minimizing soil disturbance with no-till are key strategies in regenerative row-crop production. Although living cover and no-till can increase beneficial soil carbon and water stable aggregates (WSA), annual crops in rotation with perennials often rely on herbicides to control weeds and terminate perennials. Integrated weed management (IWM) reduces reliance on herbicides by employing multiple weed control strategies including tillage and/or cultivation. However, many no-till growers are reluctant to implement some soil disturbance due to concerns about negative impacts on soil health. For that reason, we hypothesized that compared to continuous no-till and standard herbicides (NT-SH), a strategic inversion tillage in IWM (ST-IWM) would result in lower soil carbon and WSA in the year following the tillage event. We also hypothesized that soil carbon and WSA would not differ between the two systems when sampled after cover cropping and 2 years of perennials. We tested these hypotheses within a 6-year, diverse, dairy crop rotation initiated in 2010 in central Pennsylvania in a channery silt loam soil. The systems were compared in split-plots in a full crop entry experiment, where the six phases of the crop rotation were planted every year in a randomized complete block design, replicated four times. We compared the soil health indicators in spring 2010 prior to the start of the experiment and in 2013 and 2019 following inversion tillage (ST-IWM) or herbicide termination (NT-SH) of the perennial forage in the first year of the rotation. We also compared these indicators in the sixth year of the rotation after 3 years of annual and cover crops and 2 years of perennial forage. We sampled at two depths: 0–5 and 5–15 cm for total carbon and bulk density, 0–5 cm for labile carbon and 0–15 cm for WSA. Results indicate that despite initial smaller soil health values in the ST-IWM system following inversion tillage, all properties except labile carbon were similar to the NT-SH system in the sixth year of the rotation.
... Since only 70-to 120-day field experiments were carried out in this study, no significant influence was observed on the WAS under the G508 and G509 treatments. Moreover, the air-drying process before the analysis could also decrease WAS [51], although this viewpoint has not been supported by Arshad et al. [52]. ...
(1) Background: Excessive use of chemical fertilizers accelerates soil acidification and increases greenhouse gas emissions. In this context, the farmland application of organic fertilizers not only reuses agricultural waste but also improves soil quality. (2) Methods: Two organic fertilizers made from chicken manure—G508 and G509—were field applied, implementing once or twice (denoted by X1 and X2, respectively) the recommended amount of nitrogen for three crops. In addition, an incubation experiment was conducted to assess the mineralization of the organic fertilizers. (3) Results: G508 did not undergo a composting process and, thus, had a higher content of nitrogen compared to G509. Therefore, although the soil properties improved under G509, the total mineral nitrogen released was lower than G508. Compared to chemical fertilizer treatment, the application of G508 and G509 increased the soil’s pH value, concentrations of organic matter, available phosphorus, and exchangeable concentrations of potassium, calcium, and magnesium. In addition, the crop yield under G508X2 treatment was even higher than that under chemical fertilizer treatment. (4) Conclusions: Although G508 and G509 were both processed using chicken manure, they exhibited different nutrient-release behaviors during mineralization and also had different influences on the soil properties and growth of the three crops.
... This might be due to the application of organic manure that works as a cementing agent and helps to promote the formation of aggregations [5,36,40]. Soil organic matter and soil water content significantly influenced the aggregate stability of soils with contrasting cropping histories [41][42][43][44][45]. A significant relation between aggregate breakdown, crusting, and water erosion were observed [46]. ...
Continuing soil degradation remains a serious threat to future food security. Soil aggregation can help protect soil organic matter from biodegradation; it affects soil physical (aeration), chemical (water infiltration), and biological (microbial) activities. The integrated plant nutrition system (IPNS) and organic farming (OF) options have been contemplated as a sustainable strategy to sustain soil aggregate stability under adverse climatic conditions and a possible tool to restore degraded soil systems. Results suggested that the application of plant nutrients based on IPNS and soil test crop response (STCR) including mineral fertilizers and organic manure (farmyard manure:
FYM) improved soil aggregate stability and mean weight diameter (MWD) under rice–wheat cropping systems. A long-term (19 year) cropping system (rice–wheat) experiment was examined to identify best nutrient management practices. Seven nutrient supply options were applied: organic, mineral fertilizer in combination with IPNS, IPNS + B/IPNS + C to improve soil aggregate stability and MWD after completing 19 cropping cycles of rice–wheat cropping systems. Results showed that significantly higher (+31%) macroaggregates were dominant in the surface soil layer than in the subsurface soil. The significantly highest macroaggregates were observed under OF (60.12 g 100 g−1 dry soil) management practices followed by IPNS options. The MWD was significantly increased
(+17%) between surface and subsurface soil. Maximum MWD was reported with OF (0.93 mm) management practices followed by the IPNS + C (0.78 mm), IPNS + B (0.77 mm), IPNS (0.70 mm), STCR (0.69 mm), NPK (0.67 mm), and unfertilized control (0.66 mm) plots. Overall, results suggest that the adoption of IPNS options, such as organic farming (OF), RDF, STCR, and inclusion of pulses (berseem and cowpea), significantly improved all soil aggregation fractions in the soil system and also offered an additional benefit in terms of soil sustainability.
... We separated and extracted Ca-bonded organic C (Ca-SOC) and Fe\ \Al bonded organic C [Fe (Al)-SOC] using Na 2 SO 4 and Na 4 P 2 O 7 , respectively, and the C content of the extracts was measured using a TOC analyzer (TOC-V CPH, Shimadzu Scientific Instruments, Kyoto, Japan). Determination of water-stable aggregates followed the method described by Haynes and Switt (2006), where 100 g of fresh soil was soaked in water for 24 h and then placed in a 2-mm sieve that was placed atop 1, 0.5, and 0.25-mm sieves (Klute et al., 1986); water was added at a rate of 30 times/min for 2 min to facilitate aggregate grading to size. Then, content of the respective sieves was placed in a beaker, dried and weighed to derive aggregate size-class mass (M). ...
Agronomic management practices present an opportunity to improve the sustainability of crop production, including reductions of greenhouse gas emissions through impacts on soil organic carbon (SOC) dynamics. We investigated the impacts of contrasting application rates of nitrogen (N)-enriched biochar (4 and 8 t ha⁻¹) on the concentrations of total and active SOC, microbial biomass carbon (MBC), soil aggregates, and the carbon (C) pool management index (CPMI) as an indicator of soil quality in tillering and mature subtropical early and late rice in China. Soil salinity and soil bulk density increased, and soil water content generally decreased under the application of N-enriched biochar at 4 t ha⁻¹. Following the application of the biochar, there were greater soil concentrations of SOC and lower concentrations of dissolved organic-C and active labile organic‑carbon, indicating reduced mineralization and enhanced stocks of stable-C. Biochar application (4 and 8 t ha⁻¹) led to lower soil Ca-SOC concentrations and greater soil Fe(Al)-SOC concentrations. Concentrations of Fe(Al)-SOC were greater under the application of N-enriched biochar at 4 t ha⁻¹, indicating the bonding capacity of iron‑aluminum oxide and organic carbon provided by biochar improved levels of SOC fixation. The composition of soil aggregates under each treatment was mainly micro-aggregates (<0.25 mm). The greater soil content of macro-aggregates (>0.25 mm) increased under amendment with 4 t of biochar ha ⁻¹ and the greater SOC content led to greater soil aggregate stability. Levels of C pool activity, C pool index, and CPMI reduced following application of the biochar, while C pool activity index increased slightly, indicating an increase in soil quality. These results indicate that the application of N-enriched biochar during rice cultivation may lead to reductions in SOC mineralization and C emissions and increases in soil C sink capacity, due to greater SOC pool stability, thus improving the sustainability of paddy rice production.
... surface et les couches de profondeur (20-50 cm) en raison de la teneur en matière organique relativement faible, de sa dégradation rapide, et de la lixiviation des cations polyvalents dans cette partie du sol fréquemment mise à nu (Haynes et Swift, 1990 ;Amézketa, 1999). ...
RESUME La présence de la plante améliore la stabilité structurale du sol et son infiltrabilité via les résidus végétaux et l'activit é racinaire. Cette étude a été réalisée dans l'objectif d'évaluer le potentiel d'amélioration de la stabilité structurale du sol par quatre espèces végétales cultivées (bananier, canne à sucre, manioc, sorgho) en comparaison avec l'espèce Panicum maximum en jachère. Les mesures de la stabilité des agrégats à sec par la méthode Youker et McGuiness et la stabilité à l'eau par la méthode Kemper et Rosenau, ont été effectuées sur des échantillons prélevés dans les couches 0-10, 10-20, 20-30, 30-40 et 40-50 cm de profondeur. L'étude des résultats a permis de constater une amélioration de la résistance des agrégats à l'éclatement à sec sous toutes les espèces végétales cultivées par rapport à l'espèce Panicum maximum. Toutefois, la culture de canne à sucre améliore significativement (p < 0,001) la stabilité structurale du sol à sec par rapport aux autres espèces végétales étudiées mais très instable vis-à-vis de l'eau. Par ailleurs, toutes les espèces étudiées améliorent à moins de 20 % la stabilité des agrégats à l'eau bien que la culture de sorgho montre une amélioration significative (p<0,001) de l'aptitude des agrégats du sol à résister à l'action désagrégeante de l'eau dans la couche 0-10 cm en comparaison avec les autres cultures. Ces résultats prouvent que les sols du site expérimental de l'IFA-Yangambi à Kisangani sont très sensibles aux épisodes pluvieux et par voie de conséquence à l'érosion hydrique. ABSTRACT Contribution of cultivated plant species and Panicum maximum to the structural stability of the soil of the IFA-Yangambi concession in Kisangani The presence of a plant improves soil structural stability and infiltrability via plant residues and root activity. This stud y was carried out to assess the potential for improving soil structural stability by four cultivated plant species (banana, sugarcane, cassava, sorghum) in comparison with the fallow species Panicum maximum. Measurements of dry aggregate stability using the Youker and McGuiness method and wet aggregate stability using the Kemper and Rosenau method were carried out on samples taken from the 0-10, 10-20, 20-30, 30-40 and 40-50 cm depth layers. The results showed an improvement in the resistance of aggregates to dry shattering under all plant species grown compared to Panicum maximum. However, the sugarcane crop significantly (p < 0.001) improved the structural stability of the soil in the dry condition compared to the o ther plant species studied but was very unstable towards water. On the other hand, all the species studied improve the stability of aggregates to water to less than 20% although the sorghum crop shows a significant improvement (p<0.001) in the ability of soil aggregates to resist the disintegrating action of water in the 0-10 cm layer compared to the other crops. These results prove that the soils of the IFA-Yangambi experimental site in Kisangani are very sensitive to rainfall events and consequently to water erosion.
To investigate the cracking behavior in the evaporation process of the soil surface with biochar as an additive, five experimental groups were established in the natural environment with 0, 12, 60, 120, and 170 g·kg ⁻¹ biochar. The results of an investigation on organic matter and aggregations indicate that a high content of biochar can significantly improve the content of organic matter and the amount of soil aggregates. After adding 60 and 170 g·kg ⁻¹ biochar, the content of organic matter increased by 19.47% and 84.12%, respectively, and the content of soil aggregates with an average diameter greater than 0.25 mm increased by 16.43% and 38.20%, respectively. The investigation also examines the evaporation and cracking characteristics of soils that contain biochar. The rate of evaporation is approximately a “step” type function with time. The rate of evaporation is observed in three stages: the rapid, decelerating, and final evaporation stages. In the rapid evaporation stage, the initial evaporation rate of the sample that contains biochar is increased on average by 46%. The fractal dimension and cracks rate are decreased by 22.95% and 20.99% with 120 g·kg ⁻¹ biochar addition. This means that the increase of soil organic matter after adding biochar plays a crucial role in the stability of aggregates. As a soil conditioner, biochar has the ability to enhance soil water retention capacity and is a sustainable strategy to improve soil properties.
Soil stability in modern soil physics is divided into two directions: water stability and resistance to mechanical influences (compression, wedging). Both soil properties in water-saturated soil are based on the rupture of intra-aggregate interparticle bonds, however, no standard physically justified values have been proposed to characterize the stability of aggregates. The purpose of the article is to substantiate the physical concept of stability of soil aggregates and to propose a single methodological method for quantifying stability as a normative soil characteristic. A high-performance method has been developed based on the dissection of linearly arranged water-saturated aggregates using blades under controlled load. The main stages of the technique are vacuuming of aggregates to eliminate the uncontrolled influence of trapped air, saturation of aggregates in vacuum with water and subsequent determination of the aggregates stability to penetration of blades. Experimental stability values (mN/aggregate) were obtained for 17 soils, which made it possible to form normative ranges for mountainous arable heavy loamy soils: sod-podzolic – 17–19, gray forest –27–29, chernozems – 34–37 mN/agr and a number of other soils, which makes it possible to apply the obtained value as a soil characteristic of the stability of aggregates. The possibility of using the stability values as a methodological basis for monitoring soil stability and degradation, quantitative directions for assessing the state of physical characteristics of soil aggregates (first their main parameter, their stability) is discussed. Taking into account the highly correlative dependence of the proposed stability characteristic on the water stability values obtained by the Savvinov method (85%) and the high performance of the stability determination method (the proposed method is about 20 times more productive than the Savvinov method), the possibilities of using the method and the obtained values of the stability of aggregates as a general physical characteristic and a separate well for quantifying water stability are discussed.
Waste management and climate change mitigation is the key environmental challenges the world faces today. A huge quantity of industrial and agricultural wastes is generated every year globally. Dumping and burning off those wastes cause air pollution and greenhouse gases (GHGs) emissions causing global warming and climate change consequences. However, these wastes could be effectively utilized in rice as a green technology for GHGs mitigation and sustaining productivity. The seven treatments, including different dose of two industrial wastes (phosphogypsum and basic slag) and agricultural waste (rice straw, rice-straw compost, rice-straw biochar) are (i) recommended dose of fertilizer (RDF) (80:40:40:: N:P2O5:K2O kg ha−1), (ii) RDF; nitrogen through ammonium sulphate (AS), (iii) RDF + rice straw-biochar (5t ha−1) (BC), (iv) RDF + phosphogypsum (2t ha−1) (PG), (v) RDF + rice straw-incorporation (5t ha−1) (RSI), (vi) RDF + rice straw-compost (5t ha−1) (RSC), and (vii) RDF + basic slag (1t ha−1) (BS). The soil carbon-pools, enzymatic activity, GHGs emissions, global warming potential (GWP), carbon-equivalent emission (CEE), GHG intensity (GHGI) and green income (considering economic profit and carbon-credit compliance) were estimated. The BS and PG had higher GHGs emission-mitigation potential (22.3–20 and 14.8–12.9% reduction of methane and nitrous oxide over RDF, respectively) and lower GHGI. Considering yield performance, production cost, and carbon-credit compliance, BS ranked number one followed by RSC and PG in the green income category and could be promoted as green technology. However, large-scale validation in farmers’ fields is necessary for further assessment.
Background and aims Plastic mulching (PM) can improve soil aggregate stability and microbial activity, thereby preventing soil degradation in crop fields, which are different from the conditions in the orchard. However, little is known about the response of surface-soil microbial and structural stability to PM applied in orchards.
Methods An experiment was conducted from 2017 to 2020 in a pear orchard. Two treatments consisted of no mulching and plastic (black woven polypropylene fabric) lying under a pear tree canopy.
Results Results showed that the soil microbial biomass carbon content (MBC), organic carbon content (SOC), and ratio of MBC/SOC of PM treatment declined by 49.2%, 13.4%, and 41.3%, respectively. In particular, the significant decline in ratio of MBC/SOC indicated that SOC content would decrease in the future. Mean weight diameter and geometric diameter of soil aggregates in PM treatment decreased by approximately 20%, as compared with no mulching. The decrease in MBC, SOC and soil aggregates stability under PM were mainly resulted from the reduction in root exudate production and root-associated symbionts, causing by the absence of grass roots. These can be proved by the soil gas exchange and concentration. Soil respiration and mineralization were decreased by PM, but soil oxygen concentration at 10 cm depth in PM were improved, due to the oxygen consumed by microbial in no mulching treatment and low gas exchange at this depth.
Conclusions Unlike the crop field, protecting the surface soil in orchard from degradation under long-term plastic mulching application is worth considering.
The effects of both physical addition and adsorption of humic substances on the aggregation of soils were studied. To investigate the effect of adsorbed humic materials onto soils it was necessary to develop an effective adsorption procedure. Mono‐ionic soils (either sodium‐ or calcium‐saturated) were used to ensure that adsorption had occurred and to enable the results to be properly interpreted. Physical addition of humic acid followed by incubation with glucose produced aggregates with low stability values. When humic acid was adsorbed onto the soil minerals and incubated, significant increases in aggregate stability were observed which persisted with time. The stability of the re‐formed aggregates was even greater when the samples were incubated with glucose.
This work has shown that humic substances were capable of stabilization of aggregates under difficult conditions where extracellular polysaccharides were ineffective, and that the stabilization had long term persistance. It is suggested that humic substances are particularly involved in the formation of micro‐aggregates.
The effects of fumigation on organic C extractable by 0.5 M K2SO4 were examined in a contrasting range of soils. EC (the difference between organic C extracted by 0.5 M K2SO4 from fumigated and non-fumigated soil) was about 70% of FC (the flush of CO2-C caused by fumigation during a 10 day incubation), meaned for ten soils. There was a close relationship between microbial biomass C, measured by fumigation-incubation (from the relationship Biomass C = FC/0.45) and EC given by the equation: Biomass C = (2.64 ± 0.060) EC that accounted for 99.2% of the variance in the data. This relationship held over a wide range of soil pH (3.9–8.0).ATP and microbial biomass N concentrations were measured in four of the soils. The ratios were very similar in the four soils, suggesting that both ATP and the organic C rendered decomposable by CHCl3 came from the soil microbial biomass. The C:N ratio of the biomass in a strongly acid (pH 4.2) soil was greater (9.4) than in the three less-acid soils (mean C:N ratio 5.1).We propose that the organic C rendered extractable to 0.5 m K2SO4 after a 24 h CHCl3-fumigation (EC) comes from the cells of the microbial biomass and can be used to estimate soil microbial biomass C in both neutral and acid soils.
The influence of three cropping treatments on the quantitative and qualitative composition of the carbohydrate fraction of a silt loam soil and its water-stable aggregates was assessed. Three cropping treatments were considered: bromegrass (Bromus inermis Leyss.) grown continuously for 15 yr (B15), grain-corn (Zea mays L.) grown continuously using conventional tillage for 15 yr (C15), and grain-corn grown continuously for 13 yr followed by 2 yr of bromegrass (B13C2). Six water-stable aggregate size fractions ranging from 8.00–4.70 to 0.25–0.10 mm in diameter were separated from the soil by wet sieving. The carbohydrate fraction was extracted by acid hydrolysis, reduced, acetylated to alditol acetates and analyzed by temperature-programmed capillary gas chromatography. Total carbohydrate content was not significantly influenced by cropping treatment but was observed to increase as aggregate size decreased irrespective of cropping treatment. The carbohydrate content in the different aggregate size fractions...
Changes in cropping practices can alter soil structural characteristics. The purpose of this study was to assess the extent and rate at which bromegrass (Bromus inermis Leyss) and continuous grain-corn (Zea mays L.) influence soil aggregation and various soil binding agents. Five cropping treatments ranging from 15 yr of continuous grain-corn to 15 yr of continuous bromegrass production were investigated. Soil aggregation and the nature of soil binding agents were determined by measuring the water-stable aggregate size distribution subsequent to the application of six chemical pretreatments — control, distilled water, 0.08 M sodium azide, 0.08 M sodium chloride, 0.08 M sodium periodate, and 0.02 M sodium pyrophosphate. A simple power function was used to describe the relationship between the cumulative percentage by weight of water-stable aggregates and aggregate diameter. The exponent in the power function provided a measure of the influence of cropping treatment and chemical pretreatment across the whol...
Fifty years of crop rotations have decreased the stability of macroaggregates (> 250µm diameter) of Urrbrae fine sandy loam and simultaneously decreased the lengths of roots and hyphae and the percentage total organic matter in the soil. Regardless of the rotation, particles 50-250 µm diameter were very stable and were stabilized by organic matter. Practical implications of the results are discussed
The effects of growing monospecific swards of two grasses and a clover for 3 years on some physical properties of a loamy fine sand have been examined. Increases in the stability of aggregates in water (aggregation (2 mm)) occurred mainly in the surface 2 in. They were greatest under Wimmera ryegrass and least under subterranean clover. Over the 3 year period aggregation (2 mm) in the 0-3 in. layer generally increased linearly with herbage yield. Infiltration capacity was related similarly to yield of herbage in preceding years. Mulching caused insignificant aggregation changes. With increasing stability, aggregates became less dense, fractured more readily, and wet more rapidly. Despite marked increases in aggregate stability the soil reached only an 'immature' stage of structure development.
Soil aggregates have been divided into seven classes by observing the coherence of the clay fraction after reacting aggregates with water. The reactions used were: immersion of dry aggregates in water, immersion of wet remoulded aggregates in water, and suspension of aggregates in water. One further class was distinguished by the presence of carbonate. Illite and montmorillonite clays were modified so as to exhibit the physical properties of some of the aggregate classes. The results with the clays were then used to explain the characteristic properties of aggregates derived from a wide variety of soils in the various classes. For example, class 2 aggregates show partial dispersion when placed, dry, in water. The minimum percentage of exchangeable sodium present in aggregates of this class was equal to that required for dispersion of the dry Na/Ca-clays immersed in water. Examples are given of where the detection of dispersion from aggregates can be useful in the field. As only simple tests are used, the proposed method of classification can be easily carried out under field conditions.
A greenhouse experiment was conducted to investigate the effect of root growth and exudation of 3 crop species on soil aggregation. Two plant populations for each of 3 crops (corn, soybeans, and wheat) were grown in a Fincastle silt loam for 5 time periods (7, 14, 21, 28, and 41 days) and compared with fallow controls. Aggregate stability was estimated by the wet‐sieve method on both initially moist and air‐dry samples.Soil water content of initially moist soil samples varied widely among replicates, crops, and sampling dates. Wet‐sieving using initially moist soil showed that samples with higher initial soil water content had greater aggregate stability. Wet‐sieving performed on initially air‐dry soil samples was used for subsequent interpretation because the water content variable was removed.The presence of any crop and its roots in the planted soils versus the fallow controls was associated with increases in aggregate stability. No differences in aggregate stability were found among the different crops or over the established range of root length densities. Aggregate stability decreased from the original level during the first 14 to 21 days of the experiment, possibly due to daily watering. After 21 days, as root growth continued to increase, restabilization occurred until the original aggregate stability of the soil was exceeded for all crops. The observed increase in aggregate stability may be due in part to the physical entanglement of aggregates by roots and to the increased production of root exudates resulting from increased root growth.
Samples from six ash soils were chosen with a range of Fe and C contents. Stabilities over the aggregate size-range from < 1 †m to > 2 mm were measured by selectively removing aggregating agents from fresh soil samples. Wet-sieving was also carried out on both field-moist and air-dried 3.4–2.0 mm macroaggregates.
Macroaggregate stabilities were closely related to C contents and were also enhanced by high contents of allophane and/or Feox. High water contents decreased the stability of field-moist macroaggregates.
Clay-sized material was most readily dispersed with Na resin after pretreatment with hydrogen peroxide; removing the latter alone was usually ineffective in dispersing clays.
Although it has been widely established that increased crop yields follow leys sown on arable land, the relative importance of the many causative factors which may be involved is obseure. An attempt has been made to evaluate the influence of 3- to 4-year leys on the organic matter in an arable soil and to distinguish also the relative importance of the resultant change in moisture-holding capacity, crumb stability and the nitrogen status of the soil as factors in the yield of winter wheat.
An increase of about 4 tons per acre in total soil organic matter was recorded after 3 years under grazed swards. Moisture-holding capacity increased by an amount equivalent to the evapo-trans-piration loss from a full plant cover on one summer day. An increase in crumb stability was largely confined to the top inch of soil, which is effectively buried when leys are ploughed.
The influence of variation in soil nitrogen status and in crumb stability on the yield of winter wheat after leys was examined by multiple regression analysis of data obtained over a number of yean from field experiments. After allowing for the effect of variation in the nitrogen status of the soil, the influence of variation in crumb stability was insignificant Conversely variation in the nitrogen status of soils, sampled under leys before ploughing, was closely correlated (r =+0.93***) with wheat yield.
The influence of root growth and activities on soil aggregate stability was investigated using five crop species and two soils. Single plants were grown in pots for 6 weeks or less to minimise any possibility of changes in aggregate stability caused by decomposition of dead roots. Planted soils were compared with fallow controls. Aggregate stability was estimated by a turbidimetric technique (used for fresh and air-dried samples) and by wet sieving (used for air-dried samples only).
Root growth of perennial ryegrass and of lucerne for 42 days was generally associated with increases in aggregate stability whether the soil was tested in a fresh or an air-dried condition. These beneficial effects were associated with periodate-sensitive (probably polysaccharide) materials produced in the rhizosphere.
Growth of maize, tomato and wheat roots for 25 days decreased the stability of fresh soil aggregates, although the effects of tomato and of wheat were not consistent. However, the deleterious effects of these three species on aggregate stability were not apparent after air-drying. The restabilization of maize soils (relative to fallow controls) on air-drying appeared to be caused by increased stabilization by periodate-sensitive materials.
The results suggest that the growth and activities of living roots may be a major factor controlling the overall direction and magnitude of changes in aggregate stability under arable or ley crops.
When natural soil aggregates were destroyed by crushing, techniques traditionally used for re-forming aggregates, such as wetting/drying and freezing/thawing cycles, did not produce any stable re-formed aggregates. Incubation without amendment, was similarly unsuccessful, whereas incubation with glucose amendment did produce stable aggregates, and their stability was related both to the natural soil organic matter levels and to the original stability of the natural aggregates. However, the stability induced by incubation with glucose was of a transient nature and declined over a period of 12 weeks. This behaviour was attributed to the production of microbial, extracellular polysaccharides and their subsequent decomposition. Addition of microbial polysaccharides of known structure confirmed that such polymers were capable of producing stable re-formed aggregates without the assistance of further microbial activity. Longer term incubation showed that the stability of the re-formed aggregates also declined as soil micro-organisms broke down the polysaccharide material.
Neither the glucose incubation nor addition of extracellular polysaccharide was very successful in producing stable aggregates when used with soil which had been washed with salt solutions, and dialysed, to form mono-ionic soils.
Cultivating grassland changes the physical state of the soil. The paper describes observations and measurements made in the field and the laboratory on a wide range of soils (with series names) in England over a period of 25 years. Dry sieving showed that natural weathering of grassland aggregates after three months'exposure was very considerable. The drawbar-pull on ploughing soil recently out of grass, as compared with old arable, increased with the number of years out of grass.
The number of earthworms per hectare on old grassland was 6 to 9 times that on old arable of the same soil series: after three years'cultivation it was reduced by about a half.
The possibility of erosion by wind increased with the number of years out of grass. Old arable land on gentle slopes had its resistance to flowing water (sheet erosion) much increased by as little as 2 years under grass. The apparent densities of soils were at a minimum under old grass and increased under cultivation. On some soils arable for many decades, the apparent densities were near those considered limiting for root penetration. The volurne of water per cent in the soil at the sticky point decreased as the years out of grass increased, suggesting a decrease in the number of days the soil could be cultivated without smearing.
The water-stability of soil aggregates decreased as the number of years after ploughing old grassland increased. Whatever the texture, on ploughing old grassland, the water stability of air-dry aggregates feil sharply in the first – years and then approached the value corresponding to that of old arable soils more slowly, apart from soils of low clay content in which it differed little from old arable land after 2 years. Measurement of changes in water stability and field observations in a 6-course rotation (3 years ley, 3 years cereal) on a loam which had been in a similar rotation for about a decade after old grassland, suggested that this balance was probably right for maintaining such a soil at a good cropping level. Puddling (poaching) by animals of wet arable loam soils overlying clay resulted in gleying to the surface: ferrous iron was detected chemically. On putting down to grass there was little increase in water stability of the aggregates after 4 years.
The reduction in the total pore space caused by harvesting machinery and also as a result of some years'cultivation of grassland was considerable. The ease of penetration of soils when taking cores was compared by counting the number of blows to drive in a corer: the number was much less in a soil recently out of old grass compared with old arable.
The root development of cereals was poor in old arable silt soils very unstable to wetting and drying and with few visible biopores (> 10–00 μm). On soils with many visible pores, root development was much greater and yields with similar rates of nitrogen were double.
The total N in the soils feil when old grassland was ploughed, sometimes by as much as 75 per cent in about 20 years. There was sometimes a significant corre-lation between total N and the reduction in water-stable aggregation during the years following ploughing grassland: the correlation coefficient was much higher on ploughing old grassland rather than leys. The N level dropped much more quickly in the first few years after ploughing old grassland than later.
All single-property measurements give only a limited assessment of the physical state of a soil. Soils can be assessed satisfactorily only by making a range of measurements appropriate to the farming System.
The parameters of the extraction and hydrolysis of soil carbohydrates by methods involving 24N H2SO4 and N H2SO4 were studied for a sandy granitic loam. Sugars were measured by alkaline ferricyanide, orcinol, anthrone (hexoses), orcinol-ferric chloride (pentoses), cysteine-sulphuric acid (methyl pentoses), glucose oxidase (glucose), and also by analysis of the individual sugars by paper chromatography.
After shaking the soil with 24N H2SO4 at 20° C a further period of treatment with N H2SO4 at 100° C was required to obtain maximum hydrolysis of the soil carbohydrates. This period decreased from 17 h to 5 h as the time with 24N H2SO4 increased from 2 to 16 h. NH2SO4 at 100° C alone was less efficient. The extraction of pentoses by 24N H2SO4 reached a maximum within 8 h, and methyl pentoses within 4 h, both declining thereafter. The release of hexoses was continuing after 40 h.
The best compromise involved extraction with 24N H2SO4 for 16 h followed by hydrolysis with N H2SO4 for 5 h. By this treatment yields of pentoses and methyl pentoses were respectively 99 and 92 per cent of the maximum obtainable.
The stability of aggregates from 26 soils selected from agricultural areas was measured by wet-sieving and the results correlated with sand, silt, clay, nitrogen, organic matter and iron contents and with cation exchange capacity. Highly significant correlations were obtained for the relationships between aggregate stability and organic matter and some properties associated with it. No other soil constituent investigated had a significant relationship with aggregate stability, indicating that organic matter is mainly responsible for the stabilization of aggregates in these soils.
The relationships between aggregate stability, and organic matter content plus some of its component fractions were examined in more detail using 120 soils. Total organic matter, total carbohydrate and humic material extracted by various reagents each gave highly or very highly significant correlations with aggregate stability. However, whilst it was not possible to distinguish whether any one organic component was more important than another, the results indicate that soil organic matter levels can be used diagnostically to identify soils which may show problems of structural instability.
The water-stability of aggregates in many soils is shown to depend on organic materials. The organic binding agents have been classified into (a) transient, mainly polysaccharides, (b), temporary, roots and fungal hyphae, and (c) persistent, resistant aromatic components associated with polyvalent metal cations, and strongly sorbed polymers. The effectiveness of various binding agents at different stages in the structural organization of aggregates is described and forms the basis of a model which illustrates the architecture of an aggregate. Roots and hyphae stabilize macro-aggregates, defined as > 250 μm diameter; consequently, macroaggregation is controlled by soil management (i.e. crop rotations), as management influences the growth of plant roots, and the oxidation of organic carbon. The water-stability of micro-aggregates depends on the persistent organic binding agents and appears to be a characteristic of the soil, independent of management.
Benefit of leys-structural improvement of nitrogen reserves A classification of soil aggregates based on their coherence in water
- C R Emerson
CLEMENT, C.R. 1961. Benefit of leys-structural
improvement of nitrogen reserves. Journal of the
British Grassland society 16, 194-200,
EMERSON, W.W. 1967. A classification of soil aggregates based on their coherence in water. Australian
~~~~~~l ofsoif Research 5,47-57,
- K Swift
CHANEY, K. & SWIFT, R.S. 1986b. Studies on aggreture and Aggregate Stability, Conference Proceed-
Agriculture and Rural Affairs, Melbourne.
Journal of Soil Science 31,329-335.
MULVANEYv c.s' 1982' Nitrogentotal
- Bremner' J'm
BREMNER' J'M' ' MULVANEYv c.s' 1982' Nitrogentotal. In Methods of Soil Analysis (ed. A. L. Page),
pp. 565-624. Soil Science Society of America,
Madison, WI.
- G F Sowers
SOWERS, G.F. 1965. Consistency. In Methods ofsoil
Analysis, Part 1 (ed. C. A. Black), pp. 391-399.
- K Chaney
- R S Swift
CHANEY, K. & SWIFT, R.S. 1986b. Studies on aggreture and Aggregate Stability, Conference Proceed-Agriculture and Rural Affairs, Melbourne.
Journal of Soil Science 31,329-335.
Nature and Origin of Carbohydrates in Soils
- M V Cheshire
CHESHIRE, M.V. 1979. Nature and Origin of Carbohydrates in Soils. Academic Press, London.