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Recycling potassium from cow manure compost can replace potassium fertilizers in paddy rice production systems
In the potassium (K) cycle, inputs encompass all K sources that move into a given volume of soil. These inputs may include atmospheric deposition, irrigation water, runoff, erosion, as well as seeds, cuttings, and transplants. Accounting for all inputs is seldom routinely done on the farm. Many K inputs have variable concentrations, making estimations difficult. Estimates for added K are provided in some planning documents and can be used where testing of on-farm inputs is not feasible, although testing is preferred. Standard commercial fertilizers have known concentrations of K and are concentrated enough to be economical to transport long distances. The global reserves for their production have an estimated lifetime of thousands of years. This chapter emphasizes considerations for using various commercial fertilizer sources.
Potassium is an essential macroelement for rice (Oryza sativa L.), but K deficiency in paddy ecosystems has increased widely and limited sustainable rice production in China. Two‐year field trials were conducted with five K levels (0, 60, 120, 180, and 240 kg K2O ha–1, designated as K0, K60, K120, K180, and K240) in Qichun county, Hubei Province, to investigate grain yield, K uptake characteristics, and K use efficiencies of rice. The results showed that application of K increased rice yield by 9.8–29.3%, compared to K0. No significant differences were observed in rice yield among the K120, K180, and K240 treatments. The K uptake in aboveground biomass increased linearly with the K rate, while K harvest index decreased. As K uptake increased, rice yield increased linearly at first and then stabilized, showing the phenomenon of luxury consumption of K. The growth period for fast K uptake in different rice varieties and K levels was 29–67 d after transplanting, and sufficient nutrient supply is needed to ensure the increase of rice yield and growth during this period. Internal use efficiency (IUE), agronomic efficiency (AE), and physiological efficiency (PE) declined as the application rate of K increased. These results indicated that absorption and utilization of K in rice were affected by the K supply rates, and that luxury consumption occurred when K application was excessive. The luxury consumption of K by rice was mainly stored in straw.
Understanding the variables that affect the anaerobic potentially mineralizable N (PMNan) test should lead to a standard procedure of sample collection and incubation length, improving PMNan as a tool in corn (Zea mays L.) N management. We evaluated the effect of soil sample timing (preplant and V5 corn development stage [V5]), N fertilization (0 and 180 kg ha⁻¹) and incubation length (7, 14, and 28 d) on PMNan (0–30 cm) across a range of soil properties and weather conditions. Soil sample timing, N fertilization, and incubation length affected PMNan differently based on soil and weather conditions. Preplant vs. V5 PMNan tended to be greater at sites that received < 183 mm of precipitation or < 359 growing degree‐days (GDD) between preplant and V5, or had soil C/N ratios > 9.7:1; otherwise, V5 PMNan tended to be greater than preplant PMNan. The PMNan tended to be greater in unfertilized vs. fertilized soil in sites with clay content > 9.5%, total C < 24.2 g kg⁻¹, soil organic matter (SOM) < 3.9 g kg⁻¹, or C to N ratios < 11.0:1; otherwise, PMNan tended to be greater in fertilized vs. unfertilized soil. Longer incubation lengths increased PMNan at all sites regardless of sampling methods. Since PMNan is sensitive to many factors (sample timing, N fertilization, incubation length, soil properties, and weather conditions), it is important to follow a consistent protocol to compare PMNan among sites and potentially use PMNan to improve corn N management.
Measurement of soil bulk density is important for understanding the physical, chemical, and biological properties of soil. Accurate
and rapid soil bulk density measurement techniques play a significant role in agricultural experimental research. This review is a
comprehensive summary of existing measurement methods and evaluates their advantages, disadvantages, potential sources of error,
and directions for future development. These techniques can be broadly categorised as direct and indirect methods. Direct methods
include core, clod, and excavation sampling, whereas indirect methods include the radiation and regression approaches. The core
method is most widely used, but it is time consuming and difficult to use for sampling multiple soil depths. The size of the coring
cylinder used, operator experience, sampling depth, and in-situ soil moisture content significantly affect its accuracy. The clod method is
suitable for use with heavy clay soils, and its accuracy is dependent on equipment calibration, drying time, and operator experience, but
the process is complicated and time consuming. Excavation techniques are most commonly used to evaluate the bulk density of forest
soils, but have major limitations as they cannot be used in soils with large pores and their measurement accuracy is strongly influenced
by soil texture and the type of analysis selected. The indirect methods appear to have greater accuracy than direct approaches, but
have higher costs, are more complex, and require greater operator experience. One such approach uses gamma radiation, and its
accuracy is strongly influenced by soil depth. Regression methods are economical as they can make indirect measurements, but these
depend on good, quality data of soil texture and organic matter content and geographical and climatic properties. Also, like most of
the other approaches, its accuracy decreases with sampling depth.
Rice crops uptake large amounts of potassium (K), which is mainly supplied from inorganic fertilizer. Alternate K sources are essential to preserve natural reserves and to recycle unused K containing stubbles. We have evaluated the performance of rice straw (RS) in farmers' field following integrated plant nutrient system (IPNS) for supplementing K requirement of rice and compared with agro-ecological zone (AEZ)-based chemical fertilizer and farmers' practice in Tista Meander Floodplain soils of Bangladesh during 2013–2015. Application of RS @ 4.5 t ha −1 + IPNS-based fertilizer replaced full dose of chemical K fertilizer without significant reduction in grain yield of Boro rice. The K uptake with RS incorporation was similar to AEZ-based chemical fertilizer use. Considering soil health and environmental issue, RS + IPNS-based fertilizer management was the best option for growing wetland rice.
Great changes have been happened over the past 30 years in chemical fertilizer input in China, and thus a gross potassium (K) budget model established to evaluate the variation of farmland K balance for China in 1980 and 2010 at the national scale is important. Results indicated that total K input in 1980 was 6.8 million tonnes, in which chemical fertilizer, organic manure and other sources accounted for 5.6, 77.5 and 16.9% respectively. Total K input in 2010 was 21.6 million tonnes, in which chemical fertilizer, organic manure and other sources accounted for 43.5, 50.4 and 6.1% respectively. Total K output in 1980 was 8.1 million tonnes, in which crops removal and loss accounted for 98.2 and 1.8% respectively. Total K output in 2010 was 19.1 million tonnes, in which crops removal and loss accounted for 99.2 and 0.8%, respectively. Similar to K input, the spatial distribution of K output differed greatly. Total K deficit was 1.3 million tonnes, and the range of K balance in each province was −86.7 to 53.6 kg K2O ha⁻¹ in 1980. Compared with that, total K surplus was 2.5 million tonnes and the range of K balance in each province was −43.0 to 256.6 kg K2O ha⁻¹ in 2010. Chemical fertilizer K application over the past 30 years makes the great changes in average K balance from deficit to surplus in general; however, the great spatial variation in K balance drives urgent need for site-specific K nutrient management.
Improved estimates of nutrient requirements for rice (Oryza sativa L.) in China are essential to optimize fertilization regulation for increasing grain yields and reducing the potential of environmental negative influences, especially under high-yielding intensive systems. A database involving rice grain yields, nutrient concentrations and accumulations collected from on-field station experiments in the literatures published from 2000 to 2013 in China was developed to understand the relationships between grain yields and plant nutrient uptakes, and to quantify nutrient requirements for different yield levels. Considering all data sets, rice grain yield ranged from 1.4 to 15.2 t ha-1 with the mean value of 7.84 t ha-1, and ca. 10.4% of yield observations were higher than the yield barrier level of 10 t ha-1. N requirement to produce one ton grain was 21.10 kg for the yield range <4.0 t ha-1 with a high variation of 45.8%. Except of the yield range <4.0 t ha-1, the values of N requirement, firstly increased from 18.78 kg for yield range 4.0-5.5 t ha-1 to 20.62 kg for yield range 7.0-8.5 t ha-1, then decreased slightly to 19.67 and 19.17 kg for the yield range 8.5-10 and >10 t ha-1, respectively. Phosphorus (P) and potassium (K) requirements showed increasing trends, from 3.51 and 19.87 kg per t grain for <4.0 t ha-1 yield range to 4.10 and 21.70 kg for >10.0 t ha-1 range. In conclusion, nutrient requirement varied with increasement of grain yield, and N, P and K presented various response trends, increasing, declining or stagnating, which would be of great benefit for improving fertilizer strategies.
Effectof potassium (K) fertilization (0, 20, 40, 60, 80 and 100 kg K ha−1) on yield, nitrogen (N) and K nutrition of Boro (dry season) rice and apparent soil K balance were studied. Experiment was conducted at Bangladesh Rice Research Institute (BRRI) regional station (RS) farm, Habiganj, Bangladesh during 2007-2008 to 2009-2010 in a wetland rice ecosystem under haor area. Cropping pattern was Boro-Fallow-Fallow. A popular rice variety BRRI dhan29 was tested in a randomized complete block design (RCBD) with three replications. Results indicated that BRRI dhan29 maintained an average grain yield of 5.19 t ha−1 year−1 without K fertilization. Potassium fertilization significantly increased the grain yield to 6.86 t ha−1 year−1. Quadratic equations best explained the progressive increase of rice yield with increasing K rates. Optimum dose of K in three years ranged from 78 to 93 kg ha−1. Internal N use efficiency of rice decreased with increasing K rates. However, K use efficiency was inconsistent. Apparent K balance study revealed that application of 100 kg K ha−1 was not able to maintain a positive K balance in soil under wetland ecosystem with Boro-Fallow-Fallow cropping system. However, K fertilization decreased the negativity of K balance in soil.
Soil phosphorus (P) fractionation, adsorption and desorption isotherm, and rice yield and P uptake were investigated in flooded tropical rice (Oryza sativa L.) following 42-year fertilizer and manure application. The treatments included low-input [unfertilized control without N, P, or K (C0N0)], farmyard manure (FYM) (C1N0), NP (C0NP), NPK (C0NPK), FYM + NP (C1NP), and high-input treatment, FYM + NPK (C1NPK). Grain yield was increased significantly by 74% over the control under the combined application of FYM + NPK. However, under low- and high-input treatments, yield as well as P uptake was maintained at constant levels for 35 years. During the same period, high yield levels and P uptake were maintained under the C0NP, C0NPK and C1NPK treatments. These are unique characteristics of a tropical flooded ecosystem, which is a self-sustaining system for rice production. The Fe-P fraction was highest compared to the Ca-P and Al-P fractions after 42 years of fertilizer application and was significantly higher under FYM + NPK treatment. The P adsorption capacity of soil was highest under the low-input treatment and lowest under long-term balanced fertilization (FYM + NPK). In contrast, P desorption capacity was highest under NPK and lowest in the control treatment. Long-term balanced fertilization in the form of FYM + NPK for 42 years lowered the bonding energy and adsorption capacity for P in soil but increased its desorption potential, increasing P availability to the plant and leading to higher P uptake and yield maintenance.
The Mehlich 3 method for the determination of available phosphorus (P) is less laborious compared to the Olsen method and provides the advantage of multielement analysis. However, in Greece the Olsen P method is currently used because of its suitability for calcareous soils. The aims of this study were to compare (a) the Mehlich 3 and Olsen methods for 200 soils having different levels of pH and calcium carbonate and (b) Mehlich 3 colorimetric and Mehlich 3 inductively coupled plasma (ICP) analysis for 17 acidic and 23 alkaline soils. The correlation of Mehlich 3 P and Olsen P methods, excluding soils with pH less than 5 and soils with calcium carbonate levels from 10.3 to 48.3%, resulted in a linear slope of 0.24 and r2 of 0.82, and thus for this range of soils the Mehlich 3 test provided a more reliable measurement of P compared to the Olsen method. This study confirms also previous results that show that Mehlich 3 ICP test measures more P compared to Mehlich 3 colorimetry.
Management of soil phosphorus (P), potassium (K) and sulfur (S) resources in intensive, irrigated rice systems has received less attention than increasing cropping intensity and yields with new cultivars, irrigation, and fertilizer N. Crop requirements, input-output balance, and soil supplying capacity of P, K and S in irrigated lowland rice are reviewed. Based on projected rice production requirements, we estimate that the total annual nutrient demand for irrigated rice will be about 9 to 13 × 106 t N, 9 to 15 × 106 t K, 1.2 to 2.4 × 106 t P and 0.9 to 1.5 × 106 t S in 2025, amounts that represent an increase of 65 to 70% above 1990 requirements. At present, negative K balances are widespread and K deficiency has become a constraint to increasing yields, even on heavy-textured lowland soils with high inherent fertility. Because opportunities are limited for breeding cultivars that acquire more P, K or S from soil or have higher internal nutrient-use efficiencies, long-term management strategies must focus on maintaining adequate nutrient balances in the topsoil layer. Interactions among nutrients have a large influence on physiological and agronomic efficiency that result from nutrient applications. Strategies that only aim at increasing P or K application rates without considering the indigenous supply from soil reserves are inefficient; they may not sustain yield increases to meet rice demand. Little improvement in fertilizer use efficiency can be expected from the present system of providing blanket recommendations for a given production domain. Instead, site-specific nutrient-management approaches will be needed to accommodate the tremendous variability in indigenous nutrient supply found in the irrigated lowlands of Asia.
Nonexchangeable potassium (K-ne), i.e. 1 M NH4OAc-nonexchangeable K, often contributes significantly to plant nutrition. However conventional extraction methods often extract much more K-ne than plants even after intensive cropping, suggesting the difficulty in evaluating the amount of readily available soil K-ne. In this study, we used a milder extraction method (0.01 M HCl method) to examine its applicability to evaluate the amount of readily available K-ne in soil. In the first experiment, the concentration of K-ne in twenty surface soils sampled from agricultural fields in Japan and K-bearing minerals was determined by the 0.01 M HCl method, i.e. sequential extraction with 0.01 M HCl over a period of 10 d after removal of exchangeable K, and by conventional methods. The average percentage of the soil K-ne extracted by the 0.01 M HCl method amounted to 0.66% of the total K amount, and was much lower than that by a single extraction with 1 M HNO3 (2.0%) or with 0.2 M sodium tetraphenylboron for 2 d (22%). In the second experiment, the amount of K-ne removed by chemical extractions was compared with that of K-ne removed by maize plants grown for 29 d in five of the above soils. The amount of the K-ne evaluated by the 0.01 M HCl method gave the highest correlation (p < 0.05) with that of the K-ne utilized by plants among the extraction methods applied. The amount of soil K-ne extracted by the 0.01 M Hel method could therefore become a suitable index of the amount of readily available K-ne in soil. Extraction of K-ne in soils after maize planting further indicated that plants had removed K-ne more intensively than the 0.01 < HCl method probably only from the rhizosphere, although a high correlation was observed between the amount of K-ne removed by the 0.01 M Hel method and that by plants. This implies that the estimation of the amount of K-ne utilized by plants requires not only soil chemical analysis but also the evaluation of the percentage of the soil volume where the plant-induced release of K-ne actually occurs.
A long-term rice-wheat experiment was conducted at Parwanipur, Nepal, to study the effects of organic
and mineral sources of nutrients on yield and nutrient status of the soil. Twelve treatments comprising different combinations of inorganic N, P, and K; farmyard manure (FYM); and wheat chopped straw (WCS) were included. On average during a 20-year period, the control plot with an indigenous nutrient supply supported 2.06 Mg rice ha–1 and 0.69 Mg wheat ha–1. The application of 100 kg N ha–1 increased yields, but the addition of P, K, Zn, and S gave no response, indicating that the soil supply of these nutrients did not limit yield. The grain yield of rice and wheat was maintained over the years. Soil analyses of the past 6 years (1994–1999) showed that treatments receiving organic sources of nutrients increased total soil C and N from 18% to 62% and 15% to 48%, respectively, compared with the NPK treatment. There was a buildup of total P and Olsen P in plots receiving FYM. However, total and available soil K were similar in all the treatments. The apparent N and P balances for the rice-wheat system were positive in the NPK, FYM, and WCS treatments, whereas the K balance was negative in all the treatments except with the application
of FYM to both rice and wheat. Rice and wheat in most years yielded <3.15 Mg ha–1 and <2.16 Mg ha–1,
respectively. These yields are only 40–50% of the potential attainable yields of this region. Possible reasons for low yields are discussed.
A long-term soil fertility experiment (1988–1999) at the Regional Agricultural Research Station, Bhairhawa, Nepal, was analysed to determine: (1) how long the yields of rice (Oryza
sativa L.) and wheat (Triticum
aestivum L.) can be sustained without K but with N and N+P (NP) applied with or without farmyard manure (FYM) and green manure, and (2) the impact of K application on yields. Starting from the 1995 wheat season, the experiment was modified to accommodate K at 0, 42, and 84 kg ha–1 in plots receiving NP to study the response of rice and wheat to K. Both rice and wheat responded to K application but the response of wheat was substantially higher, indicating that the availability of native K may have been lower in wheat. Rice yields were lower in treatments without P than with P, and yields declined significantly (0.11–0.20 Mg ha–1 year–1) in all the treatments except in NP and NP+FYM. Wheat yield was more adversely affected than rice yield when P and K were not applied. In addition, wheat yields were low (average 0.5–2.1 Mg ha–1 in various treatments). Wheat yields declined (0.08–0.12 Mg ha–1 year–1) in all but FYM treatments indicating the role of FYM in sustaining yields. The interaction of K deficiency with Helminthosporium leaf blight (spot blotch and tan spot) is also suggested as one of the factors limiting wheat yields. The estimated K balance in soil was highly negative. Results suggest that farmers should apply adequate amount of K for higher and sustainable rice and wheat yields.
To prove the hypothesis that paddy rice utilizes soil nonexchangeable potassium (neK) and causes associated structural changes in clay minerals, K status and clay mineralogy of 22 surface soils from three paddy fields under long‐term fertilizer management for 51 ‐ 93 years were investigated. Soil neK content was determined as the difference between 1 mol L‐1 hot HNO3 extractable K and 1 mol L‐1 ammonium acetate exchangeable K. Clay mineralogy was identified by X‐ray diffraction (XRD). The radiocesium interception potential (RIP), an index of frayed edge sites in the interlayer sites of 2:1 type clay minerals, was also determined. The neK contents under the ‐K and NPK treatments were considerably lower than those under the unfertilized treatment in all the fields, indicating the exploitation of soil neK by rice. XRD analysis of the clay samples revealed 7% shift from the 1.0 nm peak to 1.4 nm one under the ‐K treatment compared with the unfertilized one, and the amounts of neK were negatively correlated with those of RIP (p<0.01), suggesting the expansion of interlayer spaces of the 2:1 type phyllosilicates such as mica due to the release of neK. In addition, the neK content positively correlated with K balance of the long‐term experiments (p<0.05). The differences of neK between unfertilized K and ‐K treatments corresponded to 22 ‐ 157 kg K ha‐1, or 0.42 ‐ 1.68 kg K ha‐1 yr‐1. In conclusion, utilization of considerable amount of soil neK under K depleted conditions should be considered to establish sustainable K management for paddy rice.
Livestock manure (LSM) is a profitable waste if handled sensibly, but simultaneously it
imposes several environmental and health impacts if managed improperly. Several
approaches have been adopted globally to cartel the problem associated with LSM
management and recovery of value-added products, still, technological innovation
needs further upgradation in consideration with the environment, energy, and
economy. This review delivered a vibrant portrait of manure management, which
includes, bioenergy generation and resource recovery strategies, their current
scenario, opportunities, challenges, and prospects for future researches along with
global regulations and policies. Several bioenergy generation and nutrient recoveries
technologies have been discussed in details, still, the major glitches allied with these
technologies are its high establishment costs, operational costs, manure assortment,
and digestate handling. This review also discussed the techno-economic assessment
(TEA) and life cycle assessment (LCA) of LSM management operation in the context of
their economical and environmental sustainability. Still, extensive researches needed
to build an efficient manure management framework to advance the integrated
bioenergy production, nutrients recycling, and digestate utilization with least
environmental impacts and maximal economical gain, which has critically discussed in
the current review.
The United Nations Sustainable Development Agenda 2030 calls for a transformative action to eradicate hunger and poverty and is particularly important for food production in developing countries (see SDG 1 Zero Hunger). Farmers in developing countries apply less potassium fertiliser than those in developed countries due to the high cost of imports and unavailability of domestic supplies. A circular economy approach can improve the efficient use of potassium resources throughout their life cycle from “mine to mouth” by identifying problem areas and assisting in designing supply strategies that help address the needs of farmers. As a nutrient, potassium conventionally follows a linear life cycle from mining. Using secondary data sources and literature, we analyse global demand and supply of potassium to quantify and illustrate the major supply shortages in the Global South.
This study identifies six options to improve potassium availability: (1) expanding conventional potassium mining and distribution systems serves those who can afford globally-traded fertiliser products; (2) seeking alternative sources of potassium, such as remineralisers, that provide a local source that is accessible to poorer farmers, and in many cases helps the circular economy of local mining operations that focus on other products; (3) improving markets by supporting trade and mitigating some of the disadvantages encountered in developing countries, such as transport and small scale of purchasing; (4) increasing the use of organic fertilisers, such as sewage and manures; (5) reusing crop residues and other farm wastes as sources of potassium, regarding a farm unit as a closed system as far as is practicable; and (6) recycling food waste so that nutrients return to the land, rather than to discard. Existing restrictions and practices mean that there is no single solution to enhance food production in the Global South using the circular economy principles. However, if these circular economy principles and policies are considered at farm to country scale progress can be made.
Southern China’s paddy soils are poor in potassium (K) and rich in iron (Fe) and aluminum (Al) oxides, both of which are affected by fertilizer application. However, the response of soil K budget to long-term K fertilization and Fe and Al oxides remains unclear, especially in the subsurface horizons in different soil types. Here, four long-term fertilization treatments (no fertilizer, CK; inorganic nitrogen and phosphorus fertilizers, NP; NPK; and the combined NPK and manure, NPKM) were selected to determine the effects of K input and different forms of Fe and Al oxides on soil K status at two soil layers (0–20, surface; and 20–40 cm, subsurface) in red (Ferralsols) and purple (Cambisols) paddy soils across China. Overall, treatments where K fertilizer application was withheld had lower surface soil exchangeable K (EK), non-exchangeable K (NEK), and total K contents than treatments applied with K fertilizer. In contrast, the treatment including K with manure fertilizer increased EK and NEK contents. Regardless of fertilization regimes, the contents of EK and NEK in both soil depths of purple soil were significantly higher than those in their corresponding depths of red soil. Moreover, there were significantly lower EK and NEK contents in the subsurface layer than those in the surface layer of red soil, while no significant differences were observed in purple soil. A positive correlation was obtained between K balances and soil EK contents (P < 0.05) and the slopes of linear regressions in red soil was higher than that in purple soil. A three-way ANOVA showed that the lone and interactive effects of experimental site, fertilization regime, and soil depth significantly influenced the contents of Fe and Al oxides in both soils. The application of NPKM can inhibit the decrease of free Fe and Al oxides in the surface layer of soil and increase the amorphous and chelated Fe and Al oxides, especially in red soil. Redundancy analysis showed that the amorphous Fe and Al oxides were the most important factors for regulating surface soil EK content. The free and chelated oxides were the most important factors for regulating NEK contents in red and purple soils, respectively, particularly in subsurface soil. Our results imply that the combined application of inorganic fertilizer and manure is a viable strategy for improving soil K availability by increasing K balance and regulating the contents and forms of Fe and Al oxides in different depths of paddy soil.
The Green Revolution (GR) made a major contribution to increasing the rice yield in the Philippines from 1.3 t ha⁻¹ in 1966 to 4.0 t ha⁻¹ in 2018, but the changes in paddy soil fertility that occurred during this 50-year period remain unknown. We collected 37 soil samples from the plow layers of paddy fields in Luzon, Leyte, Panay, and Mindanao in the Philippines in 2016 and 2017 (the ‘2010s’) and compared their fertility-related soil properties with published data for soil samples collected from the same or nearby sampling sites in 1969 (the ‘1960s’). Paddy soils in the Philippines had relatively high exchangeable calcium (Ca) and magnesium (Mg) content, cation exchange capacity (CEC), available silicon (Si) content, and total carbon (C) and nitrogen (N) content, reflecting their indigenous pedological background. We found that the 2010s soils had a lower available N content, particularly in wetter regions, despite the high input of N fertilizers, whereas the available phosphorus (P) showed a six-fold increase from the 1960s to the 2010s. The total potassium (K) content had significantly decreased during this period, possibly due to the mining effect of intensive farming with K-deficient fertilization. The 2010s soils contained a greater silt content and higher proportion of smectite in the clay fraction, which may have been transported from upstream via irrigation water. The increase in smectite corresponded with a significant increase in the cation exchange capacity, despite the organic C and clay contents tending to decrease, and these increases in smectite and soil pH may have contributed to the increase in the available fraction of Si that had not been applied as fertilizers. These findings demonstrate that paddy soil fertility in the Philippines changed in many ways over this 50-year period, largely owing to the direct impact of GR implementation in paddy fields but also potentially due to offsite effects from upland fields. The environmental impact of the nutrient loss and soil organic matter degradation behind the fertility improvement should be assessed holistically for the sustainable development of rice paddy ecosystems. (337 words)
Global dairy and swine production growth has increased significantly over the past decades, resulting in higher manure generation in certain areas and environmental concerns. Therefore, manure management is an essential focus for farmers and environmental regulators. Systematic selection of manure management practices can provide environmental benefits, but accounting for local constraints, economics and farming practices are significant challenges. All these factors drive the selection of appropriate manure management systems (MMSs). MMSs are highly varied for their design, partly due to individual farm settings, geography, and the end-use applications of manure. However, the benefits of technological advancements in MMSs provide higher manure treatment efficiency and co-production of value-added products such as recycled water, fiber, sand bedding, and nutrient-rich bio-solids, among others. To achieve higher environmental benefits, advanced manure treatment technologies have to be implemented, which comes with additional costs. So, there is a tradeoff between environmental benefits and cost. With the above prospects, this article reviews: 1) the different treatment technologies used in dairy and swine farms, 2) the life cycle assessment (LCA) method's importance in evaluating various treatment technologies for better environmental returns, and 3) decision support tools (DST) and their significance in MMSs prioritization. We found considerable heterogeneity in the available datasets, mainly on crucial parameters such as water consumption, types and amount of bedding materials, manure removal frequency, manure treatment technologies, and the extent of resource recovery. Thus, suitable environmental impact assessment inventory models are needed to evaluate a more comprehensive range of treatment technologies in MMSs, representing the spatial and farming system heterogeneities. There is also a need for user-friendly DST with adjustable inputs for the functional components of MMSs and evaluation criteria, which can rapidly evaluate the techno-economic feasibility of alternative systems.
Soil microbial communities are vital for maintaining functions of alpine wetland ecosystems, which have been shown to be sensitive to climate change and anthropogenic disturbances in recent decades. The diversity and community structure of soil bacteria and fungi are often highly heterogeneous across vegetation types and soil layers. However, the relative contributions of vegetation, soil properties, and spatial structure to variation in the microbial community remain unclear. Here, we studied the linkage between plant functional groups, soil water content, pH as well as nutrient contents and soil microbial diversity and communities in different soil layers (0–20 cm and 20–40 cm) in Lalu Wetland on the Tibetan Plateau. Plant and soil samples from eighteen plots of six sites were collected to determine the community structure of bacteria and fungi, plant functional groups, and soil characteristics. Our results showed that bacterial and fungal diversity at the 0–20 cm soil depth were significantly negatively (Shannon index, r = −0.65, P < 0.01) and positively (phylogenetic diversity, r = 0.72, P < 0.001) related to pH, respectively. Soil ammonium content was positively correlated with bacterial diversity at the 20–40 cm soil layer (Shannon index: r = 0.55, P < 0.05). Bacterial community structure was most significantly related to soil organic carbon. Fungal diversity and community structure were significantly related to soil organic carbon, available phosphorus, and available potassium. Spatial structure explained 30–50% of the variation in bacterial and fungal community structures in different soil layers in Lalu wetland. In conclusion, pH and soil nutrients were the main factors driving variation in microbial diversity and community structure in the upper and deeper soil layers, respectively. Spatial structure contributed more than vegetation and soil characteristics to explaining variation in bacterial and fungal community structures in both upper and deeper soil layers.
An ever increasing demand for animal protein products has posed serious challenges for managing the increasing quantities of livestock manure. The choice of treatment technologies is still a complicated task and considerable debates over this issue still continue. To build a clearer picture of manure treatment framework, this study was conducted to review the most frequently employed manure management technologies from its state of the art, challenges, sustainability, environmental regulations and incentives, and improvement strategies perspectives. The results showed that most treatment technologies has focused on the solid fraction of manure while the liquid fraction still remains a potential environmental threat. Compared to other waste to energy solutions, anaerobic digestion is the most mature technology to upgrade manure’s organic matter into renewable energy, however the problems associated with high investment costs, operating parameters, manure collection, and digestate management have hindered its developments in rural areas in developing countries. Bio-oil production through hydrothermal liquification is also a promising solution, as it can directly convert the wet manure into biofuel. However, lipid-poor nature of manure, operational difficulties, and the need for downstream process to remove nitrogenous compounds from the final product necessitate further research. Livestock manure management (both solid and liquid fractions) under biorefinery approach seems an inevitable solution for future sustainable development to meet circular bioeconomy requirements. Much research is still required to establish a systematic framework based on regional requirements to develop an integrated manure nutrient recycling and manure management planning with minimum environmental risks and maximum profit.
Forage rice production has increased in the rice fields in Japan. In addition, ammonia-collecting equipment has recently been developed. Liquid ammonium sulfate fertilizer (LASF) is produced through a system involving chemical cleaning (by sulfuric acid) and ammonia volatilization from compost. This study aimed to investigate the effectiveness of LASF top-dressing for forage rice. The tested rice varieties included 'Haenuki', 'Fukuhibiki', and 'Bekoaoba'. We assigned the varieties to 4 types of top-dressing treatments :1) Conventional method-chemical fertilizer, 3 kgN/10 a (CF); 2) Small amounts of fertilizer-LASF, 3 kgN/10 a (SF); 3) Moderate fertilizer-LASF, 6 kgN/10 a (MF); and 4) Large amounts of fertilizer-LASF, 9 kgN/10 a (LF). Through these treatments, the leaf color in the LF group was approximately 50% brighter than that of the CF group (p < 0.05). Plant length, the stem number and culm length in the MF and LF groups tended to show higher values than those in the CF and SF groups. Moreover, in top dry weight and crude brown rice production, MF and LF groups showed approximately 15 % higher yield than the CF and SF groups. Therefore, LASF is a suitable topdressing treatment for forage rice, and MF is suggested to be the most effective rate of application.
Organic and inorganic fertilization management in intensive cropping system is important to achieve long-term high crop yield sustainability. We quantitatively investigated crop yield sustainability through soil fertility and nutrients balance in 34-years long-term experiment under double rice cropping system in acidic paddy soil. Seven treatments were studied: CK (no fertilization); NPK (Chemical nitrogen, phosphorus and potassium fertilizer); NPM (Chemical N, P and manure); NKM (Chemical N, K and manure); PKM (Chemical P, K and manure); NPKM (Chemical N, P, K and manure) and M (Manure). Manure was applied at the rate of 45,000 kg ha −1. Results showed that crop yield and sustainability yield index under combined application of manure and chemical fertilizers was significantly higher than chemical fertilization and highest crop yield was under NPKM treatment. Long-term combined manure and chemical fertilization improved soil fertility as compared to CK and NPK treatments. Soil organic C sequestration rates under NPM, NKM, PKM and NPKM treatments were increased , while decreased under CK and NPK over the fertilization years. The uptake of N, P and K was increased over the fertilization years in all the treatments that received manure, compared with CK and NPK. Apparent K balance was negative in all the treatments. N balance (except CK and NPKM) and P balance (except CK) was positive in all fertilization treatments. P balance was exceeded the environmental risk threshold under combined application of chemical P fertilizer and manure. Boosted regression tree indicated that soil available N (AN), orgnaic carbon (OC) and total N (TN) were the most influencing factors of crop yield, accounted 36.5 %, 17.8 %, 13.4 % of variations of relative yield, respectively. Path analysis showed that long-term fertilizer inputs increased soil nutrient contents and C input directly affected soil OC. C input and soil pH indirectly influenced the relative crop yield. This study concluded that long-term combined application of manure and inorganic fertilizers increased crop yield sustainability, organic carbon sequestration rate compared to the inorganic fertilization. But long-term combined application of manure and inorganic phosphorus fertilizer increased the P balance. Therefore, rate of P inputs should be reduced under combined application of manure and inorganic P fertilizers in acidic paddy soil.
Composting is an important technology to treat biowastes and recycle nutrients, but incurs nitrogen (N) losses that lower the value of the final products and cause pollution. Technologies aimed at reducing N losses during composting have inconsistent outcomes. To deepen insight into mitigation options, we conducted a global meta-analysis based on 932 observations from 121 peer-reviewed published studies. Overall, N losses averaged 31.4% total N (TN), 17.2% NH3-N, and 1.4% N2O-N, with NH3-N accounting for 55% of TN losses. The primary drivers affecting N losses were composting method, type of biowaste, and duration of composting. N losses were significantly impacted by the carbon-to-nitrogen (C/N) ratio of the input materials (feedstock of nutrient dense biowastes and C-rich bulking agents), moisture content and pH. Our analysis revealed N-conserving optima with C/N ratios of 25-30, 60-65% moisture content and pH 6.5-7.0. In situ mitigation technologies that control feedstock and processing conditions reduced average N losses by 31.4% (TN), 35.4% (NH3-N) and 35.8% (N2O-N). Biochar and magnesium-phosphate salts emerged as the most effective N-conserving strategies, curbing losses of TN by 30.2 and 60.6%, NH3 by 52.6 and 69.4%, and N2O by 66.2 and 35.4% respectively. We conclude that existing technologies could preserve ~0.6 Tg of biowaste-N globally, which equates to 16% of the chemical N-fertilizer used in African croplands, or 39% of the annual global increases of 1.58 Tg fertilizer-N. However, the adoption of N-conserving technologies is constrained by a lack of knowledge of best practice, suitable infrastructure, policies and receptive markets. To realize an N-conserving composting industry that supports sustainable practices and the circular nitrogen economy, stakeholders have to act collectively. Benefits will include lowering direct and indirect greenhouse gas emissions associated with agriculture, and facilitating the recarbonization of soils.
After the rice harvest in Japan, rice straw (RS) is usually cut by combine harvester and incorporated into the soil to improve its fertility. In mixed crop–livestock systems, however, RS is collected and used as livestock feed, and cow dung compost (CDC) is then applied to the soil. This system utilizes the residual organic matter from both rice production and livestock husbandry to make each product. CDC application is also considered to improve the fertility of paddy soil. However, the nutrient input from CDC and the effect of CDC application on soil fertility vary among regions and/or soil types. We compared soil fertility between RS application (RS treatment, avg. 32 years) and RS removal plus CDC application (CDC treatment, avg. 21 years) in 79 paddy fields in Mamurogawa town, Yamagata Prefecture, a cold temperate region of Japan, and measured the nutrient contents in the applied RS and CDC. The total C content of RS was significantly higher than that of CDC, whereas the N, P, K, and Si contents of CDC were significantly higher than those of RS. However, there was no significant difference in paddy soil fertility – as measured by soil organic C, total N, CEC, available N, P, and Si, exchangeable K, Ca, and Mg, base saturation percentage, pH, and bulk density – between the treatments. The soil fertility of most fields was adequate by RS or CDC treatment. Thus, leaving RS in paddy fields or removing it and then adding CDC to the paddy fields has a similar effect in maintaining adequate soil fertility for single rice production or rice–livestock production systems.
Elucidating the mechanism underlying the interactive effects between nitrogen (N) and potassium (K) on rice yield is requisite to further study soil K defciency in paddy ecosystems in Southeast Asia. Field studies with combined application of four N rates (0, 90, 180, and 270 kg N ha−1) and four K rates (0, 60, 120, and 180 kg K2O ha−1) in 2013, 2014 and 2016 and a hydroponic experiment in 2017 were conducted to investigate their
effects on rice yield as well as N use efciencies (NRE). Co-application of N and K signifcantly promoted the growth and development of root and leaf, grain yield and NRE of rice. The application of N combined with zeroK increased the grain yield by 10.6–22.0%, 24.0–37.4% and 12.7–21.9% in 2013, 2014 and 2016 respectively. Similarly, leaf area index (LAI) increased by 5.9–17.9%, 8.1–19.7% and 27.9–62.7% across the three years. An increase of grain yield by 15.5–32.5%, 26.6–46.1% and 11.5–23.0% and LAI by 22.6–31.5%, 34.2–42.8% and 26.7–79.1% across the three years was recorded due to combined application of N and K. Application of higher doses of K resulted in relatively higher N uptake and N NRE. Application of K improved the N uptake and NRE by 5.6–10.0%, 7.4–16.2%, 10.9–26.4% and 12.0–22.3%, 16.9–36.4%, 20.6–43.3 % respectively across the three years. To deduct the effect of soil N and K background value, we also did a hydroponic experiment to do some physical test. In the hydroponic experiment, the leaf and root glutamine synthetase (GS), glutamate synthetase (GOGAT) and glutamate dehydrogenase (GDH) activities were signifcantly improved with the improvement of N and K. The leaf and root GS, GOGAT and GDH activity of the treatment with sufcient N and K (+N + K) was signifcantly increased by 402.3%, 332.5%, 265.2% and 200.0%, 410.4%, 239.0% respectively compared with that of the treatment with defcient N and K (-N-K). These results indicated that the combined use of N and K could further improve the grain yield as well as NRE in rice production.
With global population growth, the security of food, energy and water is becoming more challenging. Both anaerobic digestion (AD) and composting are waste management methods that are plausible approaches to address this challenge by reusing organic waste and generating value-added products. In this paper, recent research on AD and composting is summarized, and differences in the technical, economic, and environmental aspects of AD and composting, and their potential to improve the sustainability of waste management, are examined. Recent research on AD has focused on process enhancement and valorization of end products, while composting research has emphasized ways to shorten composting period and reduce odor and greenhouse gas (GHG) emissions. Strategies to enhance AD and composting processes are similar, but the operational parameters that affect microbial activity, including inoculation, aeration, temperature, moisture, C/N ratio, and pH, can differ. AD can be economically more advantageous than composting, depending on plant scale and valorization of end products, while composting is more profitable at smaller scales (e.g. < 20,000 t). Therefore, AD may be favored for centralized treatment, such as for food waste or sewage sludge; whereas, composting may be preferred for decentralized treatment, such as for on-farm animal manure. Environmentally, AD is favorable in terms of lower GHG emissions due to production of biogas as a renewable energy source. In composting, no single aeration scheme or additive has been found to be effective in reducing odor and GHG emissions simultaneously. Further research on AD and composting should be conducted to improve precision control and optimization, process design, product value, pollution control, and economic and environmental analyses, and more information needs to be provided to decision makers.
Integrating inorganic fertilizers (NPK) with organic materials have been common practices for sustainable agriculture production in low-productivity paddy soil. A 4-year field experiment was conducted to investigate the effects of the annual application of inorganic fertilizer in contrast with the combined application of organic manures and NPK on rice grain yield and the soil chemical properties. Six treatments, including control (no fertilizer), NPK alone, NPK plus spent mushroom compost at 1.5 Mg ha⁻¹ (NPK + MC), NPK plus green manure at 3.6 Mg ha⁻¹ (NPK + GM), NPK plus cattle manure at 4.7 Mg ha⁻¹ (NPK + CM), and NPK plus rice straw at 3.0 Mg ha⁻¹ (NPK + RS)—were applied in this study. The results indicated that the rice grain yields for 2014 under the NPK + CM and NPK + RS treatments were 11.4% and 9.3% higher, respectively, compared with the NPK alone treatment. No significant differences in rice yield were observed between the plots using NPK and NPK + MC or NPK + GM treatments. The application of CM to the soil surface led to significantly higher soil pH (0.16–0.29 units), cation exchange capacity (CEC) (17.4%–21.9%), and lower exchangeable acidity and Al³⁺ concentrations at soil depths of 0–20 cm, compared with the NPK alone treatment. However, no significant differences in pH or concentrations of base cations in the soil were observed in the 0–10 cm soil layer after the application of NPK alone or NPK plus the other three organic amendments. Additionally, the application of NPK + CM at 4.7 Mg ha⁻¹ y⁻¹ showed the highest available P concentration at 0–10 cm depth. Overall, the rice grain yield, soil pH, and available P were effectively improved by NPK in combination with CM at 4.7 Mg ha⁻¹.
Whole crop rice (WCR) is expected to establish a cultivation method using manure produced from animal wastes. Meanwhile, application methods of fertilizer and manure in the WCR cultivation are affected by availability of manure, available time for its application, and field drainage, and low market price of WCR. This raises concerns about soil fertility deterioration and yield reduction in the WCR cultivation. The objectives of this study were to investigate how different application methods of fertilizer and manure affected soil chemical properties and yield in the WCR cultivation. Field surveys were conducted in 2013 and 2014 at 10 fields cultivated by five different farmers in the Itoshima region, Fukuoka Prefecture, Japan. The surveyed fields included two application methods of manure (M) alone and chemical fertilizer (CF) alone. Clay plus silt content was significantly correlated with total nitrogen (TN), total phosphorus (TP), and exchangeable potassium (Exch. K), which indicated that soil texture partly contributed to the variations of these soil chemical properties. Meanwhile, clear gaps of TN, TP, Exch. K, K saturation degree, and available N between CF and M at around 40% of clay plus silt content strongly suggested that manure application contributed to increases in the soil chemical properties. Yearly differences of available N had relatively large negative values in CF fields. This result suggested a possible decrease in mineralizable part of soil TN in the WCR cultivation with CF alone, which needs to be clarified through long-term study. Significant relationships between potential N supply and straw weight (r = 0.698, p < 0.05 for 2013; r = 0.873, p < 0.01 for 2014) or yield of whole crop (r = 0.852, p < 0.01 for 2014) indicated that N mineralized from soil, which was enhanced by manure application, increased straw weight, resulting in an increase in yield of whole crop. However, excessive amounts of manure applied in surveyed fields can cause groundwater and surface water pollution. Thus, nutrient balances in a paddy field need to be analyzed further to determine an appropriate application amount of manure.
Soil mineral (or inorganic) nitrogen (SMN), which primarily exists as exchangeable and soluble ammonium (NH4⁺) and the nitrate (NO3⁻) ions, represents readily available nitrogen for plant growth. Over the years a 2M potassium chloride (KCl) solution has become the extraction solution of choice for extracting SMN. In the research and service laboratories, either distillation-titration method (DTM) or colorimetric method (CM) is virtually the standard to measure NH4⁺- and NO3⁻-N in the 2M KCl soil extracts. However, being a time-consuming and labor intensive method, DTM generally has a very low throughput. Likewise, CM is affected by interferences from pH variation, color, turbidity, presence of organic species, and some other constituents in the extracts. In contrast, diffusion conductivity method (DCM) is a less expensive and high throughput one, which is also relatively free from common interferences. In this study, we, therefore, compared the extraction efficiency of various KCl concentrations and performance of diffusion conductivity method (DCM) with DTM in measuring NH4⁺-N and NO3⁻-N in KCl extracts of 32 agricultural soils of Georgia. A 0.2M KCl solution extracted statistically similar amounts of NH4⁺-N and NO3⁻-N as did 2M KCl, suggesting that a 10-fold dilute KCl solution than the standard 2M KCl might be good enough to extract and estimate the most of SMN. For the analyses of NH4⁺- and NO3⁻-N in the KCl extracts, the DCM produced results statistically similar to those produced by DTM. The deviation between the results given by DCM and DTM was no more than ±10%. Thus, DCM appears to be an attractive alternative to the labor intensive and time-consuming DTM for measuring NH4⁺- and NO3⁻-N in the KCl extract of soils in the research and service laboratories.
The nonexchangeable potassium (neK) content of 178 agricultural soils in Japan was determined by subtracting the amount of K extracted with 1 mol L⁻¹ ammonium acetate, i.e., exchangeable K (exK) from that extracted with boiling 1 mol L⁻¹ HNO3. The statistical relationships between the neK content and physico-chemical properties of the soils were examined to investigate the factors controlling neK content. The neK content of agricultural soils in Japan ranged from 0 to 1120 mg kg⁻¹ with an arithmetic mean and median of 303 and 255 mg kg⁻¹, respectively. It showed a significant positive correlation with the total K content, fixed ammonium content, and silt content (p < 0.01) and a significant negative correlation with Alo+1/2 Feo content and total carbon content (p < 0.01). These results suggest that the controlling factors of neK are mainly the total K content and 2:1 type phyllosilicates such as mica and vermiculite, with the indirect negative influence of organic matter and amorphous materials. Terrestrial Regosols, Brown Lowland soils, and Dark Red soils had relatively high neK contents. In contrast, Andosols, Wet Andosols, and Volcanogenous Regosols had relatively low neK contents. The neK content showed no significant correlation with exK content, suggesting that neK is a moderately to slowly available fraction of soil K, which is independent of exK. In conclusion, evaluation of nonexchangeable K in combination with exchangeable K would enhance the rational management of agricultural soils in terms of K fertility by taking account of longer term K-supplying power of soils.
Large areas of the arable soils of the world are deficient in potassium (K) due to the low application rate of K fertilizer. However, current soil test methods cannot precisely determine soil available K changes. From 2009 to 2014, a field experiment was conducted in a rice–wheat cropping system in the Yangtze Plains using five K rates. The objectives were to determine the responses of wheat and rice yield to different K rates and to compare the soil available K changes extracted by three methods (ammonium acetate (NH4OAc), boiling nitric acid (HNO3), and sodium tetraphenylboron (NaTPB)). Long periods without application of K fertilizer markedly decreased wheat yield by 47% and rice yield by 15% compared with local farmers’ K practices (FKP, 90 and 120 kg K2O ha⁻¹ for wheat and rice, respectively). The FKP achieved optimal yields for wheat and rice; however, only 160% of FKP achieved a positive K balance for the cropping system. Soil-extractable K consistently decreased with increasing cropping rotations where the K rate was below 160% FKP for the three extraction methods. The extractable and changed amounts for the NH4OAC and HNO3 methods were significantly lower than that for the NaTPB method. The soil K changes for NaTPB were closer to the theoretical soil available K changes (TAKC) derived from an apparent K balance. The NaTPB method could be useful for accurately determining changes in soil available K in cropping systems.
A microfluidic hydrodynamic sequential injection (μHSI) spectrophotometric system was designed and fabricated. The system was built by laser engraving a manifold pattern on an acrylic block and sealing with another flat acrylic plate to form a microfluidic channel platform. The platform was incorporated with small solenoid valves to obtain a portable setup for programmable control of the liquid flow into the channel according to the HSI principle. The system was demonstrated for the determination of phosphate using a molybdenum blue method. An ascorbic acid, standard or sample, and acidic molybdate solutions were sequentially aspirated to fill the channel forming a stack zone before flowing to the detector. Under the optimum condition, a linear calibration graph in the range of 0.1-6mg P L⁻¹ was obtained. The detection limit was 0.1mgL⁻¹. The system is compact (5.0mm thick, 80mm wide × 140mm long), durable, portable, cost-effective, and consumes little amount of chemicals (83μL each of molybdate and ascorbic acid, 133μL of the sample solution and 1.7mL of water carrier/run). It was applied for the determination of phosphate content in extracted soil samples. The percent recoveries of the analysis were obtained in the range of 91.2-107.3. The results obtained agreed well with those of the batch spectrophotometric method.
Organic solid waste poses a serious threat to the environment as the world struggles to keep up with its rapid generation. Biological waste treatment technologies such as composting and vermicomposting are widely regarded as a clean and sustainable method to manage organic waste. The focus of this review is to evaluate the feasibility of composting and vermicomposting as a means to recover nutrients from the organic waste and returning them to the environment. The environmental impact and economic potential of these processes are also discussed. This review shows that composting and vermicomposting are capable of degrading various types of organic waste, thus enabling them to be adopted widely. The present review also reveals that greenhouse gases are emitted during composting and vermicomposting processes. However, introductions of intermittent aeration, bulking agents and earthworm abundance may reduce the greenhouse gases emissions. Economic assessments of composting and vermicomposting technologies show that these technologies are generally viable except in some cases. The differences are due to the wide range in market value for organic fertilizer and differences in cost for the type of composing or vermicomposting system which could affect its economic feasibility. However, if organic fertilizer value increases and carbon offsets are available for nutrient recycling, it will affect the economic feasibility in a positive way.
By 2050, the world's population will have reached 9 billion. To feed that many people, soil fertility will have to be maintained artificially. All fertiliser materials depend on a geological resource: nitrogen (N) fertilizer production needs fossil fuels, and both phosphate (P) and potassium (K) are derived by mining. Irrespective of new biological techniques in plant breeding and genetic modification, soils still need to supply the mineral nutrients that plants require, and these are exported from soil with every harvest.
To achieve a super high brown rice yield exceeding 10 t ha-1 in the Tohoku region (relatively cold), a two-year field experiment was conducted. The yield components, morphological traits and dry matter production among the Japonica type high-yield variety "Fukuhibiki," indica type high-yield variety "Takanari," large grain type high-yield variety "Bekoaoba" and two conventional Japonica type varieties were compared. Although the traits relating to high yield varied greatly, the three high-yield varieties all showed a large sink size, heavy rice yield at 30 days after heading (30 DAH) and a high harvest index. The effects of nitrogen application and planting density on the morphological traits, dry matter production and yield in the large grain type variety Bekoaoba were investigated. Although high nitrogen application (HN) increased the brown rice yield from 8 to 9.5 t ha-1, regulation of the timing of topdressing and/or planting density under HN could not increase the brown rice yield beyond 10 t ha-1. Strategies to achieve a super high-yield rice in the Tohoku region were discussed.
Commentators have usually viewed potash as a rather unglamorous commodity because of its limited applications, low prices, the relatively small size of the industry, a persistent supply overhang situation and high barriers to entry. Yet on closer inspection, potash provides an interesting mineral market case study.
Recently the industry has been operated as a cartel coordinated by two exporting companies—Canpotex in North America (owned by PotashCorp, Agrium and Mosaic) and the Belarusian Potash Company in the Former Soviet Union (owned by Uralkali and Belaruskali). The sector attracted new interest after 2007 when world potash prices more than doubled and the prospect of more rapidly growing demand emerged as oil and gas prices surged. Two notable recent developments have been the unsuccessful effort by BHP Billiton to acquire PotashCorp in 2010, and the attempt by Uralkali in late 2013 to increase its market share by withdrawing from its marketing agreement with Belruskali, which now seems to have been thwarted.
Considering the demand and supply sides of the industry, the current paper reflects on its recent evolution and assesses likely developments in the coming decades.
Abstract We report a high performance autonomous analytical system based on the vanadomolybdate method for the determination of soluble reactive phosphorus in seawater. The system combines a microfluidic chip manufactured from tinted poly (methyl methacrylate) (PMMA), a custom made syringe pump, embedded control electronics and on-board calibration standards. This “lab-on-a-chip” analytical system was successfully deployed and cross-compared with reference analytical methods in coastal (south west England) and open ocean waters (tropical North Atlantic). The results of the miniaturized system compared well with a reference bench-operated phosphate auto-analyser and showed no significant differences in the analytical results (student’s t-test at 95% confidence level). The optical technology used, comprising of tinted PMMA and polished fluidic channels, has allowed an improvement of two orders of magnitude of the limit of detection (52 nM) compared to currently available portable systems based on this method. The system has a wide linear dynamic range 0.1–60 μM, and a good precision (13.6% at 0.4 μM, n=4). The analytical results were corrected for silicate interferences at 0.7 μM, and the measurement frequency was configurable with a sampling throughput of up to 20 samples per hour. This portable micro-analytical system has a low reagent requirement (340 μL per sample) and power consumption (756 J per sample), and has allowed accurate high resolution measurements of soluble reactive phosphorus in seawater.
World demand for potash for agricultural purposes will continue to expand with increasing world demand for food and fiber.
World supplies of potash appear more than adequate to meet future increases in demand. However, potash reserves and production
facilities are increasingly coming under the control of national governments and in the future the industry outlook will be
affected more by political factors than by the economics of the marketplace. As a result, the private enterprise potash producer
faces a difficult time competing in a world market dominated by large, politically motivated, government-controlled companies.
In a widely-used method for particle size analysis of soils, the weight percentages of sand, silt, and clay are calculated from the density of an aqueous soil suspension measured by hydrometer. There are many versions of the procedure, differing in the type of dispersing solution, the volume of the suspension, the time of settling before taking hydrometer readings, or in the method of correcting the raw readings. Our procedure avoids errors inherent in some versions of the method, which can cause discrepancies from expected values. The details of our procedure should interest those concerned with minimizing confidence limits in inter-laboratory surveys and with providing reliable particle-size distribution data to laboratory clients.
Sample digestion is the most time‐consuming step in the elemental analysis of agricultural and food products. Moreover, a proper digestion procedure is crucial, because it affects the accuracy and precision of the analysis. In this study, a digestion procedure using sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) as digestion reagents was optimized for whole grains (chickpea, wheat, and safflower) and dry matter (wheat straw and pea). Several digestion parameters as quantity of digestion reagents either H2SO4 (2 or 3.5 mL) or H2O2 per cycle (0.5, 1, 2, or 4 mL) needed for reaction, predigestion time (5 min to overnight) and postdigestion necessarily were tested. The basic optimized procedure was 1) predigestion in 2 mL H2O2 for 10 min, 2) careful addition of 2 mL of H2SO4 followed by waiting for 5 min, and 3) performance of two digestion cycles with 2 mL H2O2 per cycle; no postdigestion step was needed. The varied conditions ensured fastest digestion, without compromising the final accuracy and precision. The digestion duration was reduced from 90–240 min to 30–45 min, and accurate results were obtained for a wide range (0.06–0.5%) of phosphorus (P) concentrations. The proposed method is suitable for determination of phosphorus and potassium (K) in complicated crop samples containing high percentages of fat, proteins, or starch, particularly in whole grains, seeds, and ground samples. The procedure is also applicable to ground samples of dry matter. Hence, there are many potential uses for the suggested improved method.
Pearl millet (Penisetum glaucum) is an interesting species to be used as cover crop in tropical areas, showing a high ability in potassium uptake. Potassium (K) is not linked to organic compounds in the plant, and can easily be released from decaying straw becoming available for subsequent crops. This experiment evaluated K leaching from millet straw grown under potassium rates (0, 100, 200, and 300 mg dm), and submitted to five levels of simulated rain (5, 10, 20, 40, and 80 mm). Plants were grown in soil filled pots in a greenhouse. On the 50th day after emergence, the plants were desiccated with glyphosate. Artificial rain was applied over the straw. Potassium deficiency speeds up millet dehydration after herbicide application and increases lightly rain water retention in the straw. The amount of K leached right after plant desiccation is correlated with the residue nutrient content and can be as high as 64 kg ha considering a mulch of 8 t ha. Although well‐nourished millet plants release considerable amounts of K with the first rains, a large percentage of the nutrient is still retained in the straw.
This review highlights future needs for research on potassium (K) in agriculture. Current basic knowledge of K in soils and
plant physiology and nutrition is discussed which is followed by sections dealing specifically with future needs for basic
and applied research on K in soils, plants, crop nutrition and human and animal nutrition. The section on soils is devoted
mainly to the concept of K availability. The current almost universal use of exchangeable K measurements obtained by chemical
extraction of dried soil for making fertilizer recommendations is questioned in view of other dominant controlling factors
which influence K acquisition from soils by plants. The need to take account of the living root which determines spatial K
availability is emphasized. Modelling of K acquisition by field crops is discussed. The part played by K in most plant physiological
processes is now well understood including the important role of K in retranslocation of photoassimilates needed for good
crop quality. However, basic research is still needed to establish the role of K from molecular level to field management
in plant stress situations in which K either acts alone or in combination with specific micronutrients. The emerging role
of K in a number of biotic and abiotic stress situations is discussed including those of diseases and pests, frost, heat/drought,
and salinity. Breeding crops which are highly efficient in uptake and internal use of K can be counterproductive because of
the high demand for K needed to mitigate stress situations in farmers’ fields. The same is true for the need of high K contents
in human and animal diets where a high K/Na ratio is desirable. The application of these research findings to practical agriculture
is of great importance. The very rapid progress which is being made in elucidating the role of K particularly in relation
to stress signalling by use of modern molecular biological approaches is indicative of the need for more interaction between
molecular biologists and agronomists for the benefit of agricultural practice. The huge existing body of scientific knowledge
of practical value of K in soils and plants presents a major challenge to improving the dissemination of this information
on a global scale for use of farmers. To meet this challenge closer cooperation between scientists, the agrochemical industry,
extension services and farmers is essential.
KeywordsPotassium availability-Potassium micronutrient interaction-Spatial availability of potassium-K/Mg ratio-Abiotic stress-Biotic stress-Frost resistance-Food quality-K/Cd relations
Nutrient budgeting is a useful tool in determining present and future productivity of agricultural land as well as undesirable
effects of nutrient mining and environmental pollution. Budgets of N, P, and K were calculated for India for 2000–2001 taking
into consideration the inputs through inorganic fertilizer, animal manure, compost, green manure, leguminous fixation, non-leguminous
fixation, crop residues, rain and irrigation water and outputs through crop uptake and losses through leaching, volatilization
and denitrification. Inorganic fertilizer was the dominant source contributing 64% of N and 78% of P inputs in Indian agriculture,
whereas K input through inorganic fertilizer was 26%. Removals of N, P, and K by major agricultural crops in the country were
7.7, 1.3 and 7.5Mt, respectively. There were positive balances of N (1.4Mt) and P (1.0Mt) and a negative balance of K (3.3Mt).
It was projected that N, P, and K requirement by Indian agriculture would be 9.78, 1.57 and 9.52Mt, respectively, to meet
the food demand of 1.3billion people by 2020. The study identified the ‘hotspots’ of excess nutrient loads as well as of
nutrient mining regions in India to improve our ability to predict environmental degradation due to imbalanced fertilizer
use. However, there are some uncertainties in India’s nutrient budget and more research is required to reduce these uncertainties.
KeywordsAmmonia volatilization-Denitrification-Fertilizer-Leaching-Manure-Nutrient balance-Nutrient uptake
Soybean-maize rotation is a profitable cropping system and is used under rain fed conditions in north China. Since crop yields
have been reported to decrease when K fertilizers are not used, we analyzed the productivity trends, soil-exchangeable and
non-exchangeable K contents, and K balance in a continuous cropping experiment conducted in an area with an alfisol soil in
the Liaohe River plain, China. The trial, established in early 1990 and continued till 2007, included 8 combinations of recycled
manure and N, P, and K fertilizers. In the unfertilized plot, the yields of soybean and maize were 1,486 and 4,124kgha−1 respectively (mean yield over 18years). The yields of both soybean and maize increased to 2,195 and 7,476kgha−1, respectively, in response to the application of inorganic N, P, and K fertilizers. The maximum yields of soybean (2,424kgha−1) and maize (7,790kgha−1) were obtained in the plots under treatment with N, P, and K fertilizers and recycled manure. K was one of the yield-limiting
macronutrients: regular K application was required to make investments in the application of other mineral nutrients profitable.
The decrease in the yields of soybean and maize owing to the absence of K application averaged 400 and 780kgha−1, respectively. Soybean seed and maize grain yields significantly increased with the application of recycled manure. For both
these crops, the variation coefficients of grain were lower with treatments that included recycled manure than without treatment.
After 18years, the soil-exchangeable and non-exchangeable K concentrations decreased; the concentrations in the case of treatments
that did not include K fertilizers were not significantly different. Treatment with N, P, and K fertilizers appreciably improved
the fertility level of the soil, increased the concentration of soil-exchangeable K, and decreased the non-exchangeable K
concentration. In soils under treatment with N, P, and K fertilizers and recycled manure, the soil-exchangeable and non-exchangeable
K levels in the 0–20cm-deep soil layer increased by 34% and 2%, respectively, over the initial levels. Both soil-exchangeable
and non-exchangeable K concentrations were the highest with on treatment with N, P, and K fertilizers and recycled manure,
followed by treatment with N, P, and K fertilizers. These concentrations were lowest in unfertilized soils; the other treatments
yielded intermediate results. The results showed a total removal of K by the crops, and the amount removed exceeded the amount
of K added to the soil; in treatments that did not include K fertilizers, a net negative K balance was observed, from 184
to 575kgha−2. The combined use of N, P, and K fertilizers and recycled manure increased the K content of the 0–20cm-deep soil layer by
125% compared to the increase obtained with the application of N, P, and K fertilizers alone. The results clearly reveal that
current mineral fertilizer applications are inadequate; instead, the annual application of recycled manure along with N, P,
and K fertilizers could sustain future yields and soil productivity.