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Cropping strategies, soil fertility investment and land management practices by smallholder farmers in communal and resettlement areas in Zimbabwe
Abstract
Three smallholder villages located in typical communal (from 1948), old (1987) and new
(2002) resettlement areas, on loamy sand, sandy loam and clay soils, respectively, were
selected to explore differences on natural resource management and land productivity. Focus
group discussions and surveys were carried out with farmers. Additionally, farmers in three
wealth classes per village were chosen for a detailed assessment of their main production
systems. Maize grain yields (t ha-1) in the communal (1.5-4.0) and new resettlement areas
(1.9-4.3) were similar but significantly higher than in the old resettlement area (0.9-2.7),
despite lower soil quality in the communal area. Nutrient input use was the main factor
controlling maize productivity in the three areas (R2=59-83%), while soil quality accounted
for up to 12%. Partial N balances (kg ha-1 yr-1) were significantly lower in the new
resettlement (-9.1 to +14.3) and old resettlement (+7.4 to +9.6) than in the communal area
(+2.1 to +59.6) due to lower nutrient applications. Averaged P balances were usually
negative. Consistently, maize yields, nutrient applications and partial N balances were higher
in the high wealth class than in poorer classes. This study found that most farmers in the new
resettlement area were exploiting the inherent soil nutrient stocks more than farmers in the
other two areas. We argue that effective policies supporting an efficient fertilizer distribution
and improved soil management practices, with clearer rights to land, are necessary to avoid
future land degradation and to improve food security in Zimbabwe, particularly in the
resettlement areas.
... Additionally, reported data on nutrient balances were extracted from the text, tables or figures, and classified by the scale(s) of evaluation and the type of study, as well as by the type of balances (partial or full balances), depending on the flows considered. Partial nutrient balances are the difference between the inflows to a system from mineral and organic fertilizers, and its respective outflows from harvested products and crop residues removed (Cobo et al., 2009); while full nutrient balances include additionally environmental flows (i.e. inputs from wet/atmospheric deposition, nitrogen fixation and sedimentation; and outputs from leaching, gaseous losses, and soil erosion) (Haileslassie et al., 2005). ...
... 52 cases out of 67 for N; 51 cases out of 52 for P) ( Fig. 2A). This is usually explained by the extended possibilities (in terms of cash, labor, livestock) of wealthier farmers for investing in soil fertility (Cobo et al., 2009), sometimes at the expense of poorer farmers (Zingore et al., 2007). In a similar way, fields near to the homestead (infields) usually had higher nutrient balances than plots of same farmers located relatively further away (outfields) (43 cases out of 48 for N, 11 cases out of 14 for P) (Fig. 2B), as farmers frequently allocate their resources and effort to the closest fields (Tittonell et al., 2007). ...
... Nevertheless, social, cultural, economical, and political conditions are also important drivers of variation on nutrient flows and balances at different scales (e.g., . For example, differences in nutrient balances between plot and farm types are usually associated not only to landscape position and specific soil fertility management practices (Haileslassie et al., 2007); but also to farmers' wealth class and even land tenure (Cobo et al., 2009). However, these factors may have less influence at a regional scale where main soil types, access to markets and climate are usually more influential (Haileslassie et al., 2007). ...
Nutrient balances are useful tools as indicators of potential land degradation and for optimizing nutrient use, and are thus highly relevant in the African context. A comprehensive literature review on nutrient balances in Africa was carried out to illustrate the main approaches, challenges, and progress, with emphasis on issues of scale. The review showed nutrient balances being widely used across the continent. The collected dataset from 57 peer-reviewed studies indicated, however, that most of the balances were calculated at plot and farm scale, and generated in East Africa. Data confirmed the expected trend of negative balances in the continent for nitrogen and potassium, where >75% of selected studies had mean values below zero. For phosphorus only 56% of studies showed negative mean balances. Several cases with positive nutrient balances indicated that soil nutrient mining cannot be generalized across the continent. Land use systems of wealthier farmers mostly presented higher nitrogen and phosphorus balances than systems of poorer farmers (p < 0.001). Plots located close to homesteads also usually presented higher balances than plots located relatively farther away (p < 0.05). Partial nutrient balances were significantly higher (p < 0.001) than full balances calculated for the same systems, but the later carried more uncertainties. The change in magnitude of nutrient balances from plot to continental level did not show any noticeable trend, which challenges prevailing assumptions that an increasing trend exists. However, methodological differences made a proper inter-scale comparison of results difficult. Actually, the review illustrated the high diversity of methods used to calculate nutrient balances and highlighted the main pit-falls, especially when nutrient flows and balances were scaled-up. Major generic problems were the arbitrary inclusion/exclusion of flows from the calculations, short evaluation periods, and difficulties on setting of spatial-temporal boundaries, inclusion of lateral flows, and linking the balances to soil nutrient stocks. The need for properly describing the methods used and reporting the estimates (i.e. appropriate units and measure of variability and error) were also highlighted. Main challenges during scaling-up were related to the type of aggregation and internalization of nutrient flows, as well as issues of non-linearity, and spatial variability, resolution and extent, which have not been properly addressed yet. In fact, gathered information showed that despite some few initiatives, scaling-up methods are still incipient. Lastly, promising technologies and recommendations to deal with these challenges were presented to assist in future research on nutrient balances at different spatial scales in Africa and worldwide.
... In fact, Shepherd and Walsh (2007) proposed that the successful "combination of infrared spectroscopy and geographic positioning systems will provide one of the most powerful modern tools for agricultural and environmental monitoring and analysis" in the next decade. The present study aims to contribute to this goal, and follows up a study from Cobo et al. (2009), in which three villages as typical cases of three settlement schemes in north-east Zimbabwe (i.e. communal area, old resettlement and new resettlement) were evaluated to determine specific cropping strategies, soil fertility investments and land management practices at each site. ...
... The assessment, however, was done at plot and farm level, and did not take into account spatial structures of soil properties. Hence, the same three villages of Cobo et al. (2009) were systematically sampled, soils characterized by MIRS, and data subsequently analyzed using conventional statistics and geostatistics tools. The main objectives of this study were: i) to evaluate advantages and disadvantages of using MIRS and geostatistics in the assessment of spatial variability of soils, ii) to test if MIRS can be directly integrated with geostatistics for landscape analyses, and iii) to present recommendations for guiding future sampling designs. ...
... Maize (Zea maiz L.) is the main crop planted in the three areas, and farmers have free access to communal grazing areas and woodlands. A full description of the sites' selection and characteristics is provided in Cobo et al. (2009). ...
Knowledge of soil spatial variability is important in natural resource management, interpolation and soil sampling design, but requires a considerable amount of geo-referenced data. In this study, mid-infrared spectroscopy in combination with spatial analyses tools is being proposed to facilitate landscape evaluation and monitoring. Mid-infrared spectroscopy (MIRS) and geostatistics were integrated for evaluating soil spatial structures of three land settlement schemes in Zimbabwe (i.e. communal area, old resettlement and new resettlement; on loamy-sand, sandy-loam and clay soils, respectively). A nested non-aligned design with hierarchical grids of 750, 150 and 30 m resulted in 432 sampling points across all three villages (730–1360 ha). At each point, a composite topsoil sample was taken and analyzed by MIRS. Conventional laboratory analyses on 25–38% of the samples were used for the prediction of concentration values on the remaining samples through the application of MIRS–partial least squares regression models. These models were successful (R2 ≥ 0.89) for sand, clay, pH, total C and N, exchangeable Ca, Mg and effective CEC; but not for silt, available P and exchangeable K and Al (R2 ≤ 0.82). Minimum sample sizes required to accurately estimate the mean of each soil property in each village were calculated. With regard to locations, fewer samples were needed in the new resettlement area than in the other two areas (e.g. 66 versus 133–473 samples for estimating soil C at 10% error, respectively); regarding parameters, less samples were needed for estimating pH and sand (i.e. 3–52 versus 27–504 samples for the remaining properties, at same error margin). Spatial analyses of soil properties in each village were assessed by constructing standardized isotropic semivariograms, which were usually well described by spherical models. Spatial autocorrelation of most variables was displayed over ranges of 250–695 m. Nugget-to-sill ratios showed that, in general, spatial dependence of soil properties was: new resettlement > old resettlement > communal area; which was potentially attributed to both intrinsic (e.g. texture) and extrinsic (e.g. management) factors. As a new approach, geostatistical analysis was performed using MIRS data directly, after principal component analyses, where the first three components explained 70% of the overall variability. Semivariograms based on these components showed that spatial dependence per village was similar to overall dependence identified from individual soil properties in each area. In fact, the first component (explaining 49% of variation) related well with all soil properties of reference samples (absolute correlation values of 0.55–0.96). This showed that MIRS data could be directly linked to geostatistics for a broad and quick evaluation of soil spatial variability. It is concluded that integrating MIRS with geostatistical analyses is a cost-effective promising approach, i.e. for soil fertility and carbon sequestration assessments, mapping and monitoring at landscape level.
... Such disruptions and incumbent practices result in a signifcant decline in yields [13]. In addition, unpredictable rainfall that results in extended dry spells and frequent droughts contributes further to the decline in agricultural productivity [21,22]. Adoption of ISFWM practices by farmers can assist greatly in increasing agricultural productivity in a sustainable manner. ...
Declining agricultural productivity has been a challenge worldwide and especially in Sub-Saharan Africa (SSA). Low agricultural productivity has been attributed to factors such as poor farm management practices, soil moisture stress, soil infertility, and soil degradation, among others. The nations in the SSA are prone to insufficient crop yields due to their inadequate capacity to adapt to good agricultural practices that support crop productivity such as integrated soil fertility and water management (ISFWM) practices. This lowers the farmers’ capacity to improve crop productivity, thus contributing in jeopardizing the food and nutritional security in SSA. Past research has shown that ISFWM strategies have not been properly adopted probably due to the lack of adequate awareness among the farmers about them. In addition, there is limited documentation on the importance of ISFWM in enhancement of soil fertility, water use efficiency, and sustainable crop production in SSA. This paper discusses some of the key ISFWM options that have the potential to enhance soil fertility, improve water use efficiency, and consequently increase agricultural productivity. The practices include intercropping, use of tied ridges, minimum tillage, mulching, and combined use of organic and inorganic fertilizers.
... For instance, soil fertility decline in Kenya due to limited soil inputs and land degradation has been reported to pose a food security issue, especially in maize production ( Karaya et al., 2012 ). Further, low and erratic rainfall worsens the situation in SSA ( Cobo et al., 2009 ). Several studies proposed animal manure as an organic resource ( Abuom et al., 2014 ;Shisanya et al., 2009 ;Mwaura et al., 2021 ), integrating inorganic with organic inputs and re- Fig. 1. ...
In sub-Saharan Africa (SSA), diminishing soil fertility has been experienced from continuous cropping and low nutrient replacement. Organic inputs and minimum tillage are proposed to increase the declining fertility of the soil to increase crop growth and yields. We reviewed animal manure and minimum tillage use on maize yields and soil organic carbon (SOC) in SSA. This involved a meta-analysis on the influence of minimum tillage and animal manure on maize grain yields and SOC. The peer-reviewed publications on animal manure and minimum tillage influence on maize yields and SOC were selected from articles that contained one or multiples of the following keywords, 'tillage, minimum tillage, conventional tillage, organic, manure, animal manure' using ScienceDirect database. Reported data on maize yields and soil organic carbon were extracted from figures, tables, and text, of the selected studies. These studies were analyzed using R, and results were presented in a forest plot. Minimum tillage had no significant influence on maize yields and soil organic carbon. Animal manure significantly improved maize yields and soil organic carbon. The study underscored the importance of animal manure in improving maize yields and soil organic carbon in SSA. Animal manure application in maize cropping systems is plausible to increase maize yields and soil organic carbon in SSA.
... These observations confirmed the perception that majority of the communal farmers had cash earnings which were too low for them to be able to buy adequate mineral fertilizer to meet soil nutrient requirements. Cobo et al. (2009) noted that with the exception of wealth families, most communal households fail to apply the recommended nutrients even the blanket recommendations because the costs are too high for them compared to their average incomes. These results imply that when abandoned fields are re-cultivated, majority of the farmers are not in a position to replenish fertility of their abandoned lands and this results in farmers getting yields which are too low and unsustainable. ...
There is need to establish whether indefinite fallows can restore soil fertility over time. A study was undertaken in 2015 to characterize fertility status of fallow fields in smallholder farming areas located in Buhera and Hwedza districts in Zimbabwe. Fallow fields were divided into four categories based on years of being fallow (0–5, 6–10, 11–20 and ≥ 20 years) across two soil types and agroecological gradient made up of four regions (AER II to V) where annual rainfall decreases from AER II to V. Soil samples were analysed for pH, N, P and K using standard laboratory methods. A survey was conducted to determine adequacy of nutrient resources used. Soil nutrients did not significantly vary (p > 0.05) with fallow age but varied with soil type and agroecological regions. Clay soils and soils from AER V had significantly high N, P and K content. In terms of adequacy of nutrients across all the three factors, N and P content were below required recommendations for crop production whilst K was adequate and soil pH was too acidic. With regards to fertilizer use, majority of the farmers failed to purchase mineral fertilizers because their annual cash earnings were far below money required. As a result 91% of the farmers were failing to apply recommended fertilizers for sustainable yields. In conclusion, fallow fields in Zimbabwe's communal areas do not restore soil fertility regardless of period to which a field has been fallow, soil texture or agroecological region. The fertility of these fallow soils remains poor and too low for crop growth. Farmers are financially unable to meet soil nutrient requirements to improve fertility of their fallow soils. These findings are important in determining appropriate measures to restore soil fertility and in determining efficient land use policing and planning measures.
... Communal farmers are aware that soil fertility is declining as shown in a study by Cobo et al. (2009) where 50 -80% of communal farmers, independent of wealth class, perceived that soil fertility has declined. Communal farmers, having noticed that maize yields were declining have been innovative in trying to address this problem. ...
There is soil fertility decline in maize (Zea mays L.)-based smallholder farming areas as a result of insufficient or lack of application of soil ameliorants. While some options can be employed such as manuring, cover cropping, intercropping and planting leguminous trees, these are often limited in terms of adaptability to very poor infertile soils and ability to give high returns on investment to encourage farmer adoption. This study sought to evaluate the potential soil fertility and maize yield benefits of hairy vetch (Vicia villosa
L.) when used in rotation or intercropped with maize. Field experiments on maize-legume rotations and relay intercropping were conducted from the 2009/2010 to 2011/2012 cropping seasons in Wedza and Chihota communal areas, and on-station at the Grasslands Research Station in Marondera. Greenhouse and field experiments were also setup during the 2011/2012 season to evaluate the effect of soil acidity and Rhizobium
leguminosarum strain on growth and N2 fixation of hairy vetch. Results from the maize legume rotation experiment showed that when legumes were basal fertilized with 300 kg ha -1 NPK fertilizer (7N : 14 P2O5 : 7 K2O), sunnhemp produced the highest aboveground biomass (7.7 t ha -1) followed by cowpea (5.9 t ha -1) and hairy vetch (2.5 t ha -1) during the first season (2009/2010). Sunnhemp also fixed more N2 (161.5 kg N ha -1) than cowpea (84.7 kg N ha -1) and hairy vetch (25 kg N ha -1). There were no significant differences (P > 0.05) in maize grain yield between basal fertilized maize that followed basal fertilised legumes and maize that was fertilised with ammonium nitrate (34.5% N) and NPK fertiliser. When relay intercropped and provided with 300 kg ha -1 NPK, sunnhemp was also superior in improving maize grain yields by at least 50% compared to
the control. Leaching tube incubations revealed that residues of hairy vetch, cowpea and sunnhemp mineralized about 18% more N than when they were mixed with maize residues. They were however, no significant differences in net N mineralized between the sole legumes residues for the 56 day incubation period. The liming and inoculation experiment revealed that there were no significant differences in biomass production of hairy vetch between limed and unlimed (acidic) soil, implying that soil acidity (pH 4.7)
was not a significant problem to hairy vetch. The R. leguminosarum strain had a significant effect on biomass production and when hairy vetch was inoculated with the strain MAR833 it fixed up to 66.5 kg N ha -1. Inoculating hairy vetch with the strain MAR833 improved its biomass production to 3.1 t ha -1 compared to the control (0.37 t ha -1). In low soil fertility conditions coupled with erratic rainfall distribution it might be
worthwhile to include sunnhemp in maize cropping systems as compared to cowpea and hairy vetch. However the potential of hairy vetch still needs to be assessed with new inoculant strains and more multi-location experiments should be done to identify a strain that can further boost its biomass production.
... Woodlands make nutrients available to crop production through woodland-field lateral transfers and through shifting cultivation. In the former, nutrients are transported to the field to boost yields [52] and sustain production on inherently infertile soils, reducing the need for chemical fertilizers and fallow periods. Common in Zimbabwe [52 -56], this largely takes the form of the transport of woodland termitaria soils or leaf litter to the fields (often mixed with manure before application). ...
Miombo and mopane woodlands are the dominant land cover in southern Africa. Ecosystem services from these woodlands support the livelihoods of 100 M rural people and 50 M urban dwellers, and others beyond the region. Provisioning services contribute $9 ± 2 billion yr−1 to rural livelihoods; 76% of energy used in the region is derived from woodlands; and traded woodfuels have an annual value of $780 M. Woodlands support much of the region's agriculture through transfers of nutrients to fields and shifting cultivation. Woodlands store 18–24 PgC carbon, and harbour a unique and diverse flora and fauna that provides spiritual succour and attracts tourists. Longstanding processes that will impact service provision are the expansion of croplands (0.1 M km²; 2000–2014), harvesting of woodfuels (93 M tonnes yr−1) and changing access arrangements. Novel, exogenous changes include large-scale land acquisitions (0.07 M km²; 2000–2015), climate change and rising CO2. The net ecological response to these changes is poorly constrained, as they act in different directions, and differentially on trees and grasses, leading to uncertainty in future service provision. Land-use change and socio-political dynamics are likely to be dominant forces of change in the short term, but important land-use dynamics remain unquantified.
This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’.
... As applied to agricultural management, balances quantify net gain or loss of nutrients over time for fields and other land units and can identify which nutrients (for example, N, P) or processes (for example, manure inputs, crop export) most limit agroecosystem productivity, suggesting leverage for innovations in practices (Berry and others 2003; Baijukya and others 2005). Mass balances have also identified crop rotations, land uses, or spatial components of systems that are most vulnerable to nutrient depletion (Elias and others 1998; Wortmann and Kaizzi 1998; Lesschen and others 2007), or suggested that relative wealth or poverty drive degradation (Elias and others 1998; Nkonya and others 2005; Yirga and Hassan 2006; Cobo and others 2009). In this study, we used nutrient balances to evaluate the relative importance of environmental, social, and management drivers on the sustainability of soil nutrient stocks in Andean agroecosystems. ...
Sustainable nutrient cycling in agroecosystems combining grazing and crops has global ramifications for protecting these ecosystems and for the livelihoods they support. We sought to understand environmental, management, and social drivers of nutrient management and sustainability in Andean grazing/crop systems. We assessed the impact of farmer wealth, fields’ proximity to villages, topography, and rangeland net primary productivity (NPP) on mass balances for nitrogen (N), phosphorus (P), and potassium (K) of 43 fields. Wealthier farmers applied greater total amounts (kg) of manure nutrients. However, higher manure application rates (kg ha−1) were associated with field proximity and NPP rather than wealth. Manure P inputs in far fields (> 500-m distant) were half those in near fields. Harvest exports increased with manure inputs (P P −1 y−1, combined mean) when calculated without erosion, but zero in near fields and negative in far fields with erosion included (−6.1 kg P ha−1 y−1 in far fields). Near/far differences in both inputs and erosion thus drove P limitation. Crop K exports dominated K balances, which were negative even without accounting for erosion. Modeled intensification scenarios showed that remediating far field deficits would require P addition and erosion reduction. Management nested within environmental constraints (NPP, erosion) rather than socioeconomic status drives soil nutrient sustainability in these agroecosystems. Time-lags between management and long-term degradation are a principal sustainability challenge to farming in these montane grazing/crop agroecosystems.
... Improvement of household food security in the sub-Saharan Africa (SSA) region has been elusive due to a combination of factors related to low and variable rainfall, poor fertility of the highly weathered soils and inappropriate soil management practices (Sanchez, 2002;Cobo et al., 2009;Belane and Dakora, 2010). Productivity in smallholder systems of Africa is further hampered by the low adoption of improved technologies with potential to increase farming output, and poor input-output market system (Dar and Twomlow, 2006). ...
Proponents of conservation agriculture (CA) argue that the CA approach offers the greatest opportunity to increase the productivity in smallholder agro-ecosystems. This study was designed to assess (1) first year maize, cowpea and sorghum yield responses to a combination of reduced tillage and mulching and (2) maize yield responses to rotation with cowpea and sorghum in reduced tillage systems. Two conservation tillage methods (ripping and planting basins) combined factorially with seven mulch levels (0, 0.5, 1, 2, 4, 8 and 10 t ha⁻¹) were compared with conventional mouldboard ploughing. The experiment was run for four consecutive growing seasons allowing for a rotation of maize, cowpea, sorghum and maize in some fields used in the study. Crop yields were determined across all tillage and mulch combinations in each year.
... Rainfed smallholder agro-ecosystems in sub-Saharan Africa are characterized by low productivity largely due to widespread soil degradation (Twomlow et al., 2006). The soils are generally infertile and the situation is exacerbated by the limited use of external nutrient inputs (Belane and Dakora, 2010;Cobo et al., 2009;Sanchez, 2002). Restoring and maintaining soil productivity remain a major challenge for smallholder agriculture in sub-Saharan Africa. ...
... They also have higher levels of input use, and reduced or even reversed levels of soil mining. This is explained by the possibility of wealthier farmers to invest in soil fertility (Cobo et al., 2009), sometimes at the expense of poor farmers (Zingore et al., 2007); i.e. nutrient fluxes from the poor farmers' fields to the rich farmers' livestock and for mulching. According to the FAO (1990), large resource availability determines the potential to acquire more farm resources for crop and livestock production by transforming the outputs into inputs for different enterprises in the agricultural system. ...
To combat soil erosion in the northern part of Taraba State, Nigeria, farmers are of major importance. Their perceptions vitally influence the levels of support and investment associated with solving problems of soil erosion through adoption of practices that are alternative to those in current use, including approaches focused on soil conservation. The objective of this study was to evaluate how farmer perceptions of soil erosion influence their investments in soil conservation, particularly soil or stone bunds, their applications of organic amendments and inorganic fertilizers and other soil conservation practices. In the study area, we undertook a field plot experiment and carried out a survey, using open- and closed-ended questions. Water erosion and depletion of fertility were taken as the main indicators of soil erosion. The results of the experiment showed that farmers were aware of and perceived both indicators as having increased over the past decade. Farmer investments in water erosion control (3.7 US$/ha) and the prevention of soil fertility depletion (37.8 US$/ha) in the study area were found to be limited. The results also showed that awareness of water erosion was only marginally correlated with investment in water erosion control (χ2 = 4.906, P = 0.09) and not associated with investments in soil fertility control measures (χ2 = 0.175, P = 0.92). Those farmers who identified depletion of soil fertility as a problem, based on erosion, were not significantly more likely to make greater investments in soil conservation (χ2 = 0.947, P = 0.62) but did invest more in fertility measures (χ2 = 3.199, P = 0.20). Hence, further research is needed to determine other factors that may influence farmer investment in soil conservation, especially factors related to socio-economic characteristics of farm households, institutional and technological innovations and field characteristics that were not addressed in this study.
The continued threat to the world's land resources is exacerbated by the protracted food crisis in sub-Saharan Africa. Per capita food production continues to decrease even though this region compares favorably with other tropical regions in terms of climate and soil resources. The main determinant of this situation is the widely recognized need for an enabling policy environment that favors smallholder rural development. However, there are two other key determinants to food security and environmental sustainability in Africa that have not received sufficient attention in the past and are the focus of this contribution: (1) the need to tackle soil fertility depletion as the fundamental biophysical constraint to food security and (2) the need for more intensive and diverse land use, based on the domestication of indigenous trees to produce high value products while increasing agroecosystem resilience. Approaches that include these three issues will transform smallholder farming in Africa into productive and sustainable enterprises and will contribute greatly to food security and environmental conservation, in a win-win situation. (C) 1997 Elsevier Science B.V.
Little is known about the in situ hydrological properties of soils in the semi-arid regions of the world where subsistence agriculture is the common land use. The work reported here concentrates on three major soil types, considered representative of the agriculturally important Zimbabwean fersiallitic group of soils, and describes the water regimes that develop under conventional (flat) and improved (tied ridge) practices in response to natural and simulated rainfall. The first soil, typical of those used by small scale farmers, is a deep coarse-grained granitic sand with a low available water capacity. The second is a silty clay loam derived from mafic rocks and typical of the red clays associated with Zimbabwe's commercial farming areas. The third is a sandy loam that readily compacts and crusts under natural rainfall, prone to runoff and thus drought sensitive. The climate at each site has a five month rainy season, when most of the rain falls as heavy convectional storms and a dry spell from April to October. However, total seasonal rainfall at each site is unreliable (200 to 1100 mm) with unpredictable dry periods of 1–3 weeks, especially at the beginning and middle of the wet season when rain occurs as intense storms of short duration. Long term monitoring of the three soil types has shown that at the end of the dry season, the quantity of water stored in the top 0.3 m of the profile is negligible, typically below permanent wilting point. Water stored in the 0.9 m profile at the end of the dry season is more variable and depends on total seasonal rainfall, its distribution, the type of crop grown and the tillage management. At the beginning of the wet season, the recharge of the soil profile is of fundamental importance for subsequent crop establishment and can benefit from improved soil water storage in the previous season and tillage practices that help to catch the first rains of the wet season. In general terms the tillage treatment that impounds the most water (tied ridges) was the wettest, whatever the soil type. However, the incomplete wetting up of the tied ridges early in the wet season, frequently resulted in poor crop establishment or a delay in planting until the ridge structure was fully wetted. This was in contrast to the conventionally tilled soils, which were more uniformly wet in the top 200 mm of the soil profile and significantly wetter than the ridged soils early in the wet season. Irrespective of tillage technique, good weed management was critical to maximize the availability of water for crop growth.
Improvement and maintenance of soil fertility is the major constraint to sustainable crop production in the communal areas (CAs) or peasant farming areas of Zimbabwe. This study assessed soil fertility status in CAs at two levels, i.e., regional and village levels. The regional soil fertility assessment was based on soil samples submitted by CA farmers to the Soil Testing Laboratory of the Chemistry and Soil Research Institute (CSRI) for analysis and fertilizer recommendations in 1992–1994. It was assumed that these samples would represent the general soil fertility conditions in the most crop production-based CAs since CSRI soil testing service is the only one normally available for farmers in the CAs. To assess soil fertility status at village level, systematic soil sampling in maize-based fields was conducted in Chinamhora and Mhondoro CAs using mapping units of 1–10 km, which would presumably capture some effects of farmer soil management on soil fertility status. The regional assessment revealed that 77% of the soils required lime (pH [CaCl2] < 5.0) for most crops, and problems of potential Al toxicity (pH [CaCl2] < 4.3) and P deficiency in over 40% of the soils. Serious problems were incidences of very low N (82%) and marginal to deficient P (84%) levels. The levels of K and Mg were generally adequate (94%). The village level assessment showed wide variations in soil properties between fields of less than 2 hectares within distances of about 1 km. This implied high probability of multiple soil fertility problems for crops in the CAs. Compared to previous assessments, the results revealed that there is a general acidification and decline in the nutrient status of CA soils. Soil fertility management effects were implied by the lower incidences of P deficiency in the more heavily fertilized Chinamhora CA, and lower incidences of potential Al toxicity and low K at the regional level than at village level which suggested greater use of acidifying N fertilizers and more depletion of soil K under maize. Acidification and depletion of nutrients may become even greater constraints to crop production in the CAs if the trend continues, especially under maize.
Many commentators on African agriculture believe soil fertility is declining to levels where food production can no longer be sustained, thus spelling disaster for the future. But how accurate are these doomsday pictures? This paper takes a more focused look at the issues of soil fertility management using a case study from southern Zimbabwe. An historical perspective is taken which attempts to unravel the range of factors which have influenced the changes in soil fertility at landscape and farm levels over the past century. The story that emerges is not one of terminal decline, but one where some areas have increased in fertility status through active enrichment through management, while others have declined. The role of institutions, both local and external, in mediating the processes of soil fertility change is highlighted through an examination of the patterns of labour organisation, land tenure, government legislation and markets and prices. The resulting story, not surprisingly, is much more complex than the simplistic commentaries so often dominating environmental and agricultural policy debates. The implications of this complexity for planning and policy are briefly discussed.
Based on the results of an erosion damage assessment in Southern Zimbabwe, where mechanical conservation work has been carried out since the 1940s, this paper describes the impact of mechanical conservation systems on processes leading to rill erosion. In a study of a catchment area, it was found that influxes of water from roads and waterways as well as contour ridges that were originally designed to control rill erosion had a major role in the formation of rills. Existing rills and depressions which cause water concentration, siltation of contour drains and overflowing of contour ridges were the main factors leading to excessive rill erosion. The study showed that particularly during a highly erosive year like 1992/93, the damage due to rill erosion can be excessive, causing an abrupt degradation.It is concluded that the present conservation system is insufficient to control rill erosion effectively and is often the cause of this erosion. Effective control of rill erosion is a pre-condition for optimal implementation of land management systems such as conservation tillage. Therefore, an integrated approach to land husbandry must be developed jointly with farmers and promoted in order to improve crop production and sustainable management of natural resources. This should consider improved mechanical conservation as well as agronomic and biological soil and water conservation techniques.
Zimbabwe's fast track land reform has generated significant attention in southern Africa and beyond due to its speed, scale and the forced displacement of land owners and farm workers. Less attention however, has been paid to the broader framework which has been used to support this rapid and often careless transformation of rural Zimbabwe. Land reform is a means not an end. It is a means to address issues of inequality, historical injustices, inefficiencies in production and distribution, poverty in communal areas, et al. In sum, land reform provides the means to achieve complex goals to make life better for some people without harming, certainly not in the longer term, the productive base of a national economy. While arguments for land reform have been well-articulated including resisting globalization and western domination, the national government and ruling party of Zimbabwe have not directly expressed their views of what Zimbabwe should be like following its land reform. It is a surprising silence given the importance that the land issue played in the constitutional referendum of 2000 and the following parliamentary and presidential elections and the growing economic crises in Zimbabwe. In one effort to examine the potential consequences of fast track land reform, Sam Moyo and Paris Yeros in their recent book suggest that Zimbabwe is on the cusp of a national democratic revolution. In contrast, this paper examines the little that is known about the vision for Zimbabwe's rural areas in the government owned press and statements by the ZANU-PF political leadership. It asks what are the most likely potential paths given the rich historical, legal and ethnographic literature on rural Zimbabwe? It examines what we might expect in the context of what we know about the ruling party and how the state has acted in the recent past toward its communal and resettlement areas. It will also consider what class forces will be like in the contemporary period and therefore why there will not be any 'revolution' but rather the continued impoverishment of rural families unless they have wage earners abroad. It is argued that fast track land reform has diminished rather than expanded the possibilities for a genuine transformation of rural society. In turning its back upon the multiple changes in production, distribution and consumption that have characterized Zimbabwe since 1990, ZANU-PF seeks a repeasantized and politically loyal subject population that will not contest the party's nationalization of key national resources for its own benefit.
An improved understanding of soil fertility variability and farmers’ resource use strategies is required for targeting soil fertility improving technologies to different niches within farms. We measured the variability of soil fertility with distance from homesteads on smallholder farms of different socio-economic groups on two soil types, a granite sand and a red clay, in Murewa, northeast Zimbabwe. Soil organic matter, available P and CEC decreased with distance from homestead on most farms. Soil available P was particularly responsive to management, irrespective of soil type, as it was more concentrated on the plots closest to homesteads on wealthy farms (8–13mgkg−1), compared with plots further from homesteads and all plots on poor farms (2–6mgkg−1). There was a large gap in amounts of mineral fertilizers used by the wealthiest farmers (>100kg N and >15kg P per farm; 39kgNha−1 and 7kgPha−1) and the poorest farmers (13kgPha−1), but decreased to 10–20N and 6–9kg P per plot (
An appreciation of the dynamism of the links between soil resources and society provides a platform for examining food security
over the next 50 years. Interventions to reverse declining trends in food security must recognize the variable resilience
and sensitivity of major tropical soil types. In most agro-ecosystems, declining crop yield is exponentially related to loss
of soil quality. For the majority smallholder (subsistence) farmers, investments to reverse degradation are primarily driven
by private benefit, socially or financially. “Tragedy of the commons” scenarios can be averted by pragmatic local solutions
that help farmers to help themselves.
Issues of land and further resettlement are central within the inter related crises that Zimbabwe is currently understood to be experiencing. This paper presents objective data that has not been available to date, concerning the landscape outcomes of the resettlement programme in Zimbabwe as it was implemented in the first two decades after independence. Sequential aerial photograph interpretation and GIS techniques are used to document and explore spatial patterns of resource use, landscape structure and change. Based on 21 resettlement villages across three scheme areas, the analysis explicitly considers the role of national drivers (of the relatively consistent policy and procedures during that time), of agro-ecology and of multidirectional transformations at the village level to raise understanding of these outcomes. The implications of these findings and the value of the methodological techniques for the design and monitoring of further resettlement in the country and the wider region are suggested. Copyright © 2006 John Wiley & Sons, Ltd.
Nutrient depletion is a major constraint to crop production for moist savanna soils, and inputs of nutrients are required to overcome this constraint. The impact of sole and combined applications of organic inputs (OIs) [fresh tree prunings, Pueraria phaseoloides (Roxb.) Benth. residues, and manure] and urea [(NH2)2CO] on maize (Zea mays L.) performance was investigated at four sites in West Africa. Interactions between OIs and urea resulting in added benefits from their mixed rather than sole application were quantified, and likely causes were evaluated. Maize in the mixed treatments, receiving 45 kg ha-1 urea N and 45 kg ha-1 N as OIs, produced 1.6 and 3.7 Mg ha-1 grain in Sékou and Glidji, respectively. Based on the yields from sole application of either OIs or urea, added benefits from the mixture were 0.49 Mg ha-1 grain (P < 0.001) in Sékou and 0.58 Mg ha-1 (P < 0.15) in Glidji. These benefits were generated during grain filling, which was characterized by drought, and they were likely caused by improved soil water conditions with mixed applications compared with sole applications. Nitrogen recovery from urea was higher in the combined treatments (44% in Sékou and 32% in Glidji) relative to the sole urea treatments (22% in Sékou and 15% in Glidji). Positive interactions between OIs and urea occurred at two of four sites and were likely caused by improved soil water conditions after applying OIs. Organic inputs can alleviate constraints to crop growth other than N depletion and, as such, improve the use efficiency of N fertilizer.
This paper examines the emergence of a complex socio-political and economic conflict over unequal land and natural resources control in Zimbabwe, focusing on the post independence period from 1980. Colonial expropriation of agricultural land and vast natural resource reservoirs, such as indigenous woodlands, water systems and wildlife resources, established a dualistic political-economic landscape characterised by competing resource ownership structures and multifaceted conflicts. Race dominance of natural resources by a white settler minority class of 4000 commercial farmers with an average of 200 hectares and large scale tourists operators, alongside large state controlled but leased forest and wildlife conservancies marginalized about 1.5 million peasants families, and other sub-altern classes from the access to key resources. The latter depend on natural resources for most of their basic livelihoods needs. Throughout the first 20 years of independence this extractive system remained unchanged and was worsened by increased demand for land by a growing rural and unemployed urban population. Neoliberal land reform and environmental management policies based on private property relations applied to commercial farmers' land rights vis-à-vis 'communal tenure' and partially decentralized land and natural resources management systems, with limited financial and infrastructural investments failed to assuage historic grievances over resource control and the growing fragility of livelihoods among the poor. An export oriented structural adjustment programme, favouring elite natural resources utilization and which led to wide economic decline, ignited popular struggles to regain land. A combination nationalist elite interests and peasants movements challenged the existing property relations of white minority and the 'rule of law' on which these inequities were founded, through a lands occupation or seizure process. A radical land redistribution programme based on land expropriation was initiated by the state in 2000, leading to the reallocation of the prime commercial lands to over 150 000 peasants and about 1600 new black sized farmers. While the redistribution resolved overarching inequities it has led to a series of political, economic and resource conflicts underlain by economic decline, and a second generation of inequities. Resolving these new resource conflicts remains a key challenge.
A quarter of a century after independence the distribution of land has become the dominant issue in Zimbabwe, the focal point of political upheaval and the reason behind Zimbabwe's departure from the Commonwealth. Attempts to resolve the issue in the 1980s were thwarted by scarce resources, escalating land values and a failure to turn donor pledges into cash. The issue resurfaced in the late 1990s, symbolized by occupations by ‘war veterans’ against a background of violence and intimidation. The controversial fast track programme that emerged transformed land ownership structure in Zimbabwe, with white commercial farmers losing about 78% of their land to black farmers, but at a huge price to the Zimbabwean people.
The extraction of earth alkaline and alkali metals (Ca, Mg, K, Na), heavy metals (Mn, Fe, Cu, Zn, Cd, Pb) and Al by 1 M NH4NO3 and 0.5 M NH4Cl was compared for soil samples (texture: silt loam, clay loam) with a wide range of pH(CaCl2) and organic carbon (OC) from a forest area in W Germany. For each of these elements, close and highly significant correlations could be observed between the results from both methods in organic and mineral soil horizons. The contents of the base cations were almost convertible one-to-one. However, for all heavy metals NH4Cl extracted clearly larger amounts, which was mainly due to their tendency to form soluble chloro complexes with chloride ions from the NH4Cl solution. This tendency is very distinct in the case of Cd, Pb, and Fe, but also influences the results of Mn and Zn. In the case of Cd and Mn, and to a lower degree also in the case of Pb, Fe, and Zn, the effect of the chloro complexes shows a significant pH dependency. Especially for Cd, but also for Pb, Fe, Mn, Zn, the agreement between both methods increased, when pH(CaCl2) values and/or contents of OC were taken into account. In comparison to NH4Cl, NH4NO3 proved to be chemically less reactive and, thus, more suitable for the extraction of comparable fractions of mobile heavy metals. Since both methods lead to similar and closely correlated results with regard to base cations and Al, the use of NH4NO3 is also recommended for the extraction of mobile/exchangeable alkali, earth alkaline, and Al ions in soils and for the estimation of their contribution to the effective cation-exchange capacity (CEC). Consequently, we suggest to determine the mobile/exchangeable fraction of all elements using the NH4NO3 method. However, the applicability of the NH4NO3 method to other soils still needs to be investigated.
Designed experiments conducted by crop scientists often give rise to several random sources of variation. Pertinent examples are split-plot designs, series of experiments and repeated measurements taken on the same field plot. Data arising from such experiments may be conveniently analysed by mixed models. While the mixed model framework is by now very well developed theoretically, and good software is readily available, the technology is still under-utilized. The purpose of the present paper is, therefore, to encourage more widespread use of mixed models. We outline basic principles, which help in setting up mixed models appropriate in a given situation, the main task required from users of mixed model software. Several examples are considered to demonstrate key issues. The theoretical underpinnings are briefly sketched in so far as they are practically relevant for making informed use of mixed-model computer packages. Finally, a brief review is given of some recent methodological developments, which are of interest to the plant sciences. A German version of this paper is available from the corresponding author upon request.
The African Green Revolution is starting to gain momentum and there is now optimism about sub-Saharan Africa’s ability to
rapidly increase its agricultural productivity. This is partly due to some key successes—at the local and national levels—of
policies that support smallholder farmers. The 80 Millennium Villages, which comprise approximately 400,000 people in ten
countries of sub-Saharan Africa, have drastically increased production of staple food crops, transforming food deficits into
crop surpluses. Maize yields more than doubled at the village scale, from 1.7 to 4.1tons ha−1. In Malawi, because of a smart input subsidy program implemented by the government, maize harvests have greatly surpassed
those of previous years, turning that country from a recipient of food aid into a food exporter and food aid donor to neighboring
countries. Other countries are beginning to implement similar efforts. They will require novel financial mechanisms from the
donor community to support them adequately. There is little question that sub-Saharan Africa can greatly improve food security
with an ecologically-sound African Green Revolution supported by science-based policies, community mobilization, gender empowerment
and effective governance.
The continued threat to the world's land resources is exacerbated by the protracted food crisis in sub-Saharan Africa. Per capia food production continues to decrease even though this region compares favorably with other tropical regions in terms of climate and soil resources. The main determinant of this situation is the widely recognized need for an enabling policy environment that favors smallholder rural development. However, there are two other key determinants to food security and environmental sustainability in Africa that have not received sufficient attention in the past and are the focus of this contribution: (1) the need to tackle soil fertility depletion as the fundamental biophysical constraint to food security and (2) the need for more intensive and diverse land use, based on the domestication of indigenous trees to produce high value products while increasing agroecosystem resilience. Approaches that include these three issues will transform smallholder farming in Africa into productive and sustainable enterprises and will contribute greatly to food security and environmental conservation, in a win-win situation.
We discuss the temporal and spatial dynamics of nutrient resources and water within cropping and livestock systems, their interactions and those with other resources such as labour. Short-term dynamics (within season) revolve around nutrient availability and losses as a function of soil moisture dynamics. Longer-term effects (multiple seasons and years) are related to residual effects of crop management in successive seasons and to changes in soil organic matter contents.Spatial patterns of resource use are consistent across different tropical farming systems. Farmers preferentially allocate manure, mineral fertilizers and labour to fields close to the homestead, resulting in strong negative soil fertility gradients away from the homestead. Livestock are the central means of concentration of nutrients within farming systems, resulting in their inequitable redistribution from common lands and poorer households to richer households. Productivity gains achieved by concentration on home plots are at the expense of long-term declining productivity on remote fields. Restricted availability of inputs leads to a form of self-organization resulting in repeating patterns of farm organization that are recognisable across sub-Saharan Africa.Principles for enhancing allocation efficiency of scarce resources are required that address the dynamics of interacting temporal and spatial scales. Managed variability that creates gradients of soil fertility can have major effects on resource use efficiency of both nutrients and water, necessitating analysis of trade-offs at farm scale. Investment decisions of farming families are shaped through complex interactions among competing demands for investment of cash and labour within and beyond farm boundaries. Combinations of socio-economic and agro-ecological conditions can provide windows of opportunity in both time and space that favour investment in particular forms of management.Past research provides a vast array of technologies to improve agricultural production, and understanding of the underlying processes. A research framework is proposed representing farm systems as sets of interacting components. This framework can be used ex-ante, to assist in targeting technologies to specific types of farmers, and for identification of more appropriate technologies. It can be used to explore short and long-term trade-offs of management strategies and to evaluate effects of policy on farms varying in resource endowment.
There is a need for an improved understanding of nitrogen (N) dynamics in depleted sandy soils in southern Africa. A field experiment was conducted to evaluate the performance of different soil fertility improvement practices on a degraded granitic sandy soil in Zimbabwe. Legumes capable of accumulating large amounts of N through biological N2 fixation and subsoil N capture were tested against soybean/maize rotation, cattle manure fertilization and continuous maize (Zea mays L) with or without fertilizer. Soybean (Glycine max) accumulated 82 kg ha−1 N (seed+stover), while mucuna (Mucuna pruriens) produced 87 kg ha−1 N in its biomass. Soybean fixed 76% of its N, while mucuna fixed 96% of the accumulated N as estimated by the natural abundance method. Although the following maize crop in the second season suffered from drought stress, maize N uptake was 14.8 kg ha−1 following soybean and 16.4 kg ha−1 following mucuna, compared with 5.2 kg ha−1 for the unfertilized maize and 25.6 kg ha−1 for the maize fertilized with N at 90 kg ha−1. Cajanus cajan and Crotalaria paulina added barely 10 kg ha−1 of N through their biomass and had no effect on N uptake by maize. Apparent recovery of the added N by maize was 47% for the fertilized maize, 36% for soybean, 12% for mucuna and 9% for cattle manure. There was very little partitioning of N into grain and uptake was mostly before the onset of the drought. Despite the large differences in added residue N, differences in soil mineral N were only evident up to 4 weeks after the beginning of the rains, after which mineral N concentrations became very small in all treatments due to leaching, rather than crop uptake. By the eighth week after crop emergence, maize root length density had increased to about 0.1 cm cm−3 at the 60–80 cm depth, the rapid increase apparently stimulated by the drought. It was concluded that mineral N available to maize from the residues tested falls short of what is required to sustain high maize yields. In these environments where biomass accumulation in many legumes is restricted by soil biophysical factors (poor nutrient concentrations, acidity, coarse texture), combinations of legume rotations and mineral N fertilization will remain the most viable option for sustainable agriculture.
A model, designed to carry out soil nutrient audits, has been used to calculate nutrient balances for Africa for the period 1961–1998 for land used for arable and permanent crops. The model indicates that in Africa and most African countries, nutrient depletion has been increasing and in 1998 was 3.5 million tonnes nitrogen (17.4 kg N ha−1 year−1). The corresponding data for phosphorus were 0.7 million tonnes (3.3 kg P ha−1 year−1), and for potassium, 4.1 million tonnes (20.0 kg K ha−1 year−1). Average total nutrients output (embodied in crop output) increased by 2.5% year−1 between 1961 and 1998, but in the same period, output capita−1 per year fell by about 10%.Nutrient audits for six countries in SSA (Kenya, Malawi, Nigeria, Uganda, Zambia and Zimbabwe), for the period 1961–1998, show large differences in input and output rates and balances. In 1996–1998, total nutrient inputs (N+P+K) ranged from 23 kg ha−1 year−1 (Zambia) to 81 kg ha−1 year−1 (Zimbabwe). Total nutrient output (crop production) for the corresponding period was in the range 21 kg ha−1 year−1 (Zambia) to 97 kg ha−1 year−1 (Nigeria). Nutrient balance time series show that for most countries, N, P and K nutrient depletion rates have increased between 1961 and 1998 but have fluctuated considerably during this period. The depletion rate in Nigeria has increased threefold since 1980 and in 1998 was 73 kg ha−1 year−1. Because both inputs and outputs were low, Zambia had the lowest total nutrient depletion rate of 5 kg ha−1 year−1. In all cases, the highest depletion rates are for K.To achieve a sustainable nutrient output per capita will require a large increase in fertilizer use. It is unlikely that these consumption rates will be achieved and hence future food security could be impaired. Policy implications are discussed.
Soil fertility decline is perceived to be widespread in the upland soils of the tropics, particularly in sub‐Saharan Africa. Most studies have used nutrient balances to assess the degree and extent of nutrient depletion; these have created awareness but suffer methodological problems as several of the nutrient flows and stocks are not measured. This chapter focuses on the assessment of soil fertility decline using soil chemical data (pH, organic C, total N, available P, cation exchange capacity (CEC), and exchangeable cations) that are routinely collected in soil surveys or for the assessment of fertilizer recommendations. Soil fertility decline can be assessed using a set of properties from different periods at the same site or from different land‐use systems with the same soils. The former is easier to interpret; the latter can be rapidly collected but differences may be due to inherent differences and not have resulted from soil management. This study provides an analytical framework for the assessment of soil fertility decline and shows pitfalls and how they should be handled. Boundary conditions are presented that could be used in future studies on soil fertility management and crop productivity in the tropics.
A 2-year study was conducted in three rainfall zones of Zimbabwe to explore opportunities for harnessing biological nitrogen fixation of non-cultivated herbaceous legumes, which hitherto have been regarded simply as weeds, in order to improve soil productivity on smallholder farms. The rainfall zones used ranged from sub-humid (800 mm annually) to semi-arid (<650 mm). Nitrogen is the single most important crop nutrient under the predominantly leached sandy soils of southern Africa, and alternative N sources are lacking for smallholder farmers. Diversity and abundance of indigenous legume species were determined under different land uses using farmer participatory research techniques among other methods. Over 30 different legume species, mainly of the genera Crotalaria, Indigofera and Tephrosia, were identified across the three agro-regions. With the participation of farmers, a simple technique, termed the gwezu smell technique, was developed which enabled participating farmers to distinguish between legumes and non-leguminous plants. Diversity was higher in areas with less than 20 years of cropping compared with old farming areas with over 70 years of cultivation, suggesting that prevailing management practices have over time rendered soil environments unfavourable for productivity and regeneration of these legumes.
Organic resources play a critical role in both short-term nutrient availability and longer-term maintenance of soil organic matter in most smaller holder farming systems in the tropics. Despite this importance, there is little predictive understanding for the management of organic inputs in tropical agroecosystems. In this paper, an organic resource database (ORD) is introduced that contains information on organic resource quality parameters including macronutrient, lignin and polyphenol contents of fresh leaves, litter, stems and/or roots from almost 300 species found in tropical agroecosystems. Data on the soil and climate from where the material was collected are also included, as are decomposition and nutrient release rates of many of the organic inputs. Examples of uses of ORD are provided in the paper: (1) nutrient contents (including median values and ranges) and other resource quality parameters of farmyard manure and crop residues are compared to that of alternative nutrient sources such as different plant parts and plant types; (2) nutrient stocks found in farm boundary hedges are estimated and evaluated as a source of nutrients for soil fertility management; (3) hypotheses regarding the indices and critical values of N, lignin, and polyphenol contents for predicting N release rates are tested; (4) organic materials for soil fertility management experiments are selected. This database, when coupled with models and decision support tools, will help advance organic matter management for soil fertility improvement from an empirical to a predictive practice.
This paper reviews current organic nutrient management practices and their integration with mineral fertilizers in Sub-Saharan Africa with a view to understanding the potential impacts on a range of input markets. A number of different organic nutrient management practices have been found to be technically and financially beneficial, but they differ considerably as to their effectiveness and resource requirements. A review of African smallholder experiences with integrated soil fertility management practices finds growing use, both indigenously and through participation in agricultural projects. Patterns of use vary considerably across heterogeneous agroecological conditions, communities and households, but are stimulated by profitable commercially oriented agricultural opportunities. The potential for integrated soil fertility management to expand markets for organic inputs, labor, credit, and fertilizer is explored. We found that there are few direct analyses of these links and indirect evidence at this point in time is inconclusive.
Evidence on the performance of Zimbabwe’s early land reform effort is mixed. In this paper we use a unique micro data set with information on land reform beneficiaries and a control group of nonbeneficiaries and employ propensity score matching to examine household and per capita benefits associated with land reform. Combining this information with estimates on the cost of land reform we find that the economic return is positive but modest. Its magnitude depends on assumptions about the opportunity costs of land and the reasons for the observed increase in the size of resettled households.
Indigenous soil fertility management strategies in semi-arid Communal Areas of Zimbabwe have largely been driven by an extensive use of resources. The shrinking of common property resources (CPRs) due to expansion of cultivated lands, the general loss of productivity in natural ecosystems (e.g., poor grazing) and increasing demand for nutrient sources due to the increased number of farming households have resulted in a critical scarcity of the traditional sources of nutrients. Although farmers use many locally derived fertilizers (e.g., leaf litter, manure or termitaria), they do so more in desperation than by choice. Because of their low quality and declining availability, locally derived fertilizers fall short of satisfying crop growth requirements for the current market-oriented economy. Such inputs also require a lot of labor for collection and transport, often for little return in soil fertility improvement. There should therefore be a limit to which we can expect to manipulate farmer innovativeness or exploit indigenous knowledge systems in order to sustainably manage soil fertility. Farmers have probably done their best under the prevailing circumstances. The study by Scoones et al. (1996) gives examples of how farmers have adopted and fine-tuned technologies to suit a variety of circumstances. This raises a major issue of whether indigenous soil fertility management and practices in semi-arid Communal Areas can be improved without introducing major changes to the farming systems. The answer depends on the level of production that it is hoped farmers can achieve. If yields above subsistence production levels are expected, then the idea of low-input agriculture in these marginal environments is nonsensical. As population pressure continues to increase, the major challenge in semi-arid communal Areas is that of transforming an extensive management system into an intensive one. This involves changes in extension strategies, farmers attitudes and perceptions and a concomitant change in resource utilization. It therefore requires an interdisciplinary and integrated approach and should be expected to take time. Current indigenous soil fertility management practices are dependent on CPRs. Net nutrient outflows from these ecosystems are likely to result in declining productivity of CPRs. Households in semi-arid areas get significant income from forestry products (Clarke et al. 1996) e.g., crafts and wood carvings. Intensification of soil fertility management on arable lands will save forestry resources and spare these ecosystems from degradation. Under the current management practices, the only viable nutrient sources are manure and crop residues
We discuss the temporal and spatial dynamics of nutrient resources and water within cropping and livestock systems, their interactions and those with other resources such as labour. Short-term dynamics (within season) revolve around nutrient availability and losses as a function of soil moisture dynamics. Longer-term effects (multiple seasons and years) are related to residual effects of crop management in successive seasons and to changes in soil organic matter contents. Spatial patterns of resource use are consistent across different tropical farming systems. Farmers preferentially allocate manure, mineral fertilizers and labour to fields close to the homestead, resulting in strong negative soil fertility gradients away from the homestead. Livestock are the central means of concentration of nutrients within farming systems, resulting in their inequitable redistribution from common lands and poorer households to richer households. Productivity gains achieved by concentration on home plots are at the expense of long-term declining productivity on remote fields. Restricted availability of inputs leads to a form of self-organization resulting in repeating patterns of farm organization that are recognisable across sub-Saharan Africa. Principles for enhancing allocation efficiency of scarce resources are required that address the dynamics of interacting temporal and spatial scales. Managed variability that creates gradients of soil fertility can have major effects on resource use efficiency of both nutrients and water, necessitating analysis of trade-offs at farm scale. Investment decisions of farming families are shaped through complex interactions among competing demands for investment of cash and labour within and beyond farm boundaries. Combinations of socio-economic and agro-ecological conditions can provide windows of opportunity in both time and space that favour investment in particular forms of management. Past research provides a vast array of technologies to improve agricultural production, and understanding of the underlying processes. A research framework is proposed representing farm systems as sets of interacting components. This framework can be used ex-ante, to assist in targeting technologies to specific types of farmers, and for identification of more appropriate technologies. It can be used to explore short and long-term trade-offs of management strategies and to evaluate effects of policy on farms varying in resource endowment.
The government of Zimbabwe launched the Fast Track Land Reform Programme (FTLRP) in 2000 as part of its ongoing land reform and resettlement programme aimed at addressing a racially skewed land distribution. Its goal has been to accelerate both land acquisition and redistribution, targeting at least five million hectares of land for resettlement. This paper investigates the impact of the FTLRP on its beneficiaries’ perceptions of land tenure security, and how these subsequently impacted soil conservation investments. Evidence suggests that the programme created some tenure insecurity, which adversely affected soil conservation investments among its beneficiaries. We find support for the contention that households invest in land-related investments to enhance security of tenure. The results underscore the need for the government of Zimbabwe to clarify and formalise land tenure arrangements within the programme.
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