Soil Use and Management
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Sustainable agricultural development in sub‐Saharan Africa: the case for a paradigm shift in land husbandry Abstract In order to tackle poverty and hunger in sub‐Saharan Africa (SSA) there is a strong case for a focus of effort on improving rainfed agricultural systems. The challenge is to deliver a transformation of agricultural productivity in such systems without adverse impacts on environmental goods and services. We examine the growing advocacy of ‘conservation agriculture’ (CA) as the desired approach and assess the evidence to support the assertion that it can deliver sustainable agricultural development in SSA. We examine in particular the evidence which derives from experience with ‘zero tillage sustainable agriculture’ in Brazil. We ask the question, is there a case for a paradigm shift in land husbandry? The case for a paradigm shift hangs on the premise that conventional practice promotes land degradation, while adoption of CA practice delivers a range of benefits through promoting soil ecosystem health. The guiding principle is to promote biological tillage through minimizing mechanical soil disturbance and maintaining permanent organic soil cover. We examine evidence of benefits in the context of the wider debate on low‐external‐input technology. We conclude that CA does not overcome constraints on low‐external‐input systems and will deliver the productivity gains that are required to achieve food security and poverty targets only if farmers have access to fertilizers and herbicides. We conclude also that widespread adoption of the new paradigm amongst millions of small farmers in order to achieve the ‘doubly green revolution’ in SSA is subject to the familiar constraints of knowledge transfer and success will depend upon creating innovation networks. Further, we conclude that amongst small‐scale farmers partial adoption will be the norm and it is not clear that this will deliver soil health benefits claimed for full adoption of the new paradigm.
Soil Use and Management - Tập 24 Số 1 - Trang 92-99 - 2008
A lysimeter study of nitrate leaching from grazed grassland as affected by a nitrification inhibitor, dicyandiamide, and relationships with ammonia oxidizing bacteria and archaea Abstract Nitrate (NO3 − ) can contribute to surface water eutrophication and is deemed harmful to human health if present at high concentrations in the drinking water. In grazed grassland, most of the NO3 − ‐N leaching occurs from animal urine‐N returns. The objective of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO3 − leaching in three different soils from different regions of New Zealand under two different rainfall conditions (1260 mm and 2145 mm p.a.), and explore the relationships between NO3 − ‐N leaching loss and ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA). The DCD nitrification inhibitor was found to be highly effective in decreasing NO3 − ‐N leaching losses from all three soils under both rainfall conditions. Total NO3 − ‐N leaching losses from the urine patch areas were decreased from 67.7–457.0 kg NO3 − ‐N/ha to 29.7–257.4 kg NO3 − ‐N/ha by the DCD treatment, giving an average decrease of 59%. The total NO3 − ‐N leaching losses were not significantly affected by the two different rainfall treatments. The total NO3 − ‐N leaching loss was significantly related to the amoA gene copy numbers of the AOB DNA and to nitrification rate in the soil but not to that of the AOA. These results suggest that the DCD nitrification inhibitor is highly effective in decreasing NO3 − leaching under these different soil and rainfall conditions and that the amount of NO3 − ‐N leached is mainly related to the growth of the AOB population in the nitrogen rich urine patch soils of grazed grassland.
Soil Use and Management - Tập 25 Số 4 - Trang 454-461 - 2009
Identification and quantification of organic phosphorus forms in soils from fertility experiments Abstract The effects of soil type, crop rotation, fertilizer type and application rate on the composition of organic phosphorus (P ) compounds in soils from four sites in a S wedish long‐term fertilizer experiment were investigated with 31 P ‐NMR . Soil textures investigated were loamy sand, sandy loam, silty clay loam and clay. Phosphorus has been added to the soils since the 1950s and 1960s at four different rates in the form of either mineral fertilizer or a combination of manure and mineral fertilizer. Results show that in soils receiving no P addition, most of the soil P was present in the form of phosphate monoesters (60–70%, depending on soil type). However, a P addition equivalent to the amount of P removed annually by harvest altered this relationship so that the soils were dominated by orthophosphate instead. This trend became more obvious with increasing P addition. At the greatest P application rate, orthophosphate comprised 70% or more of the total extracted P in all the soils. These changes in the soil were due entirely to increase in orthophosphate, because the amounts of monoesters did not change with increasing P additions. This was true both for mineral fertilizer and the combination of manure and mineral fertilizer P . Soil type and crop rotation did not influence the results. The results indicate that there is no apparent build‐up of organic P in the soils, but that P addition mainly affects the orthophosphate amounts in the soils regardless of form or amount of fertilizer.
Soil Use and Management - Tập 29 Số s1 - Trang 24-35 - 2013
Leaching of nitrate and phosphorus after autumn and spring application of separated solid animal manures to winter wheat Abstract Animal slurry can be separated into solid and liquid manure fractions to facilitate the transport of nutrients from livestock farms. In Denmark, untreated slurry is normally applied in spring whereas the solid fraction may be applied in autumn, causing increased risk of nitrate and phosphorus (P) leaching. We studied the leaching of nitrate and P in lysimeters with winter wheat crops (Triticum aestivum L.) after autumn incorporation versus spring surface application of solid manure fractions, and we compared also spring applications of mineral N fertilizer and pig slurry. Leaching was compared on a loamy sand and a sandy loam soil. The leaching experiment lasted for 2 yr, and the whole experiment was replicated twice. Nitrate leaching was generally low (19–34 kg N/ha) after spring applications of mineral fertilizer and manures. Nitrate leaching increased significantly after autumn application of the solid manures, and the extra nitrate leached was equivalent to 23–35% of total manure N and corresponded to the ammonium content of the manures. After spring application of solid manures and pig slurry, only a slight rise in N leaching was observed during the following autumn/winter (<5% of total manure N). Total P leaching was 40–165 g P/ha/yr, and the application of solid manure in autumn did not increase P leaching. The nitrogen fertilizer replacement value of solid manure N was similar after autumn and spring application (17–32% of total N). We conclude that from an environmental perspective, solid manure fractions should not be applied to winter wheat on sandy and sandy loam soils under humid North European conditions.
Soil Use and Management - Tập 28 Số 1 - Trang 1-11 - 2012
Long-term nitrogen supply from cattle slurry
Soil Use and Management - Tập 21 Số 2 - Trang 196-204 - 2005
Effectiveness of different precipitated phosphates as phosphorus sources for plants Abstract. Eleven precipitated phosphates were evaluated as sources of phosphorus (P) for plant growth by comparing their effectiveness with that of monocalcium phosphate, a source of water soluble P that is generally considered to be fully plant available. The precipitated phosphates comprised struvites recovered from waste water discharges (mainly magnesium ammonium phosphate), laboratory synthesised struvites, a synthetic iron phosphate and a recovered calcium phosphate. Precipitating phosphates in these forms could be a way for removing P from waste water before it is discharged to rivers, so reducing the risk of eutrophication. Application to agricultural land would be one potential use for such phosphates. Evaluation was by pot experiments with a sandy loam soil and with a sandy clay loam soil using perennial ryegrass (Lolium perenne) as the test crop. The soils differed in pH (6.6 and 7.1) and in Olsen P (28 and 11 mg L−1 ). Measured variables were grass dry matter (DM) yield and grass P concentration which were used to calculate offtake of P in the harvested grass. DM yields of ryegrass and P offtakes given by the synthetic and recovered struvites were not significantly different statistically either between themselves or to MCP applied at the same rate. On this basis these struvites could be used to recycle P to similar soils and the effect of the P on crop yield should be similar to that of MCP
Soil Use and Management - Tập 19 Số 1 - Trang 45-49 - 2003
How geostatistics can help you Abstract. Geostatistics is basically a technology for estimating the local values of properties that vary in space from sample data. Research and development in the last 15 years has shown it to be eminently suited for soil and ripe for application in soil survey and land management. The basic technique, ordinary kriging, provides unbiased estimates with minimum and known variance. Data for related variables can be incorporated to improve estimates using cokriging. By more elaborate analysis using disjunctive kriging the probabilities of deficiency and excess can be estimated to aid decision.The variogram is crucial in all geostatistics; it must be estimated reliably from sufficient data at a sensible scale and modelled properly. Once obtained it can be used not only in the estimation itself but also to choose additional sampling sites, improve a monitoring network or design an optimal sampling scheme for a survey. It may also be used to control a multivariate classification so that the resulting classes are not too fragmented spatially to manage.
Soil Use and Management - Tập 7 Số 4 - Trang 206-217 - 1991
Using soil organic matter fractions as indicators of soil physical quality Abstract The objective of this study was to evaluate the use of chemical and physical fractions of soil organic matter (SOM ), rather than SOM per se , as indicators of soil physical quality (SPQ ) based on their effect on aggregate stability (AS ). Chemically extracted humic and fulvic acids (HA and FA ) were used as chemical fractions, and heavy and light fractions (HF and LF ) obtained by density separation as physical fractions. The analyses were conducted on medium‐textured soils from tropical and temperate regions under cropland and pasture. Results show that soil organic carbon (SOC ), SOM fractions and AS appear to be affected by land use regardless of the origin of the soils. A general separation of structurally stable and unstable soils between samples of large and small SOC content, respectively, was observed. SOM fractions did not show a better relationship with AS than SOC per se . In both geographical regions, soils under cropland showed the smallest content of SOC , HA and carbon concentration in LF and HF , and the largest HF /LF ratio (proportion of the HF and LF in percent by mass of bulk soil). With significant associations between AS and SOC content (0.79**), FA /SOC (r = −0.83** ), HA /FA (r = 0.58** ), carbon concentration of LF (r = 0.69** ) and HF (r = 0.70** ) and HF /LF ratio (r = 0.80** ), cropland showed lowest AS . These associations indicate that SOM fractions provide information about differences in SOM quality in relation to AS and SPQ of soils from tropical and temperate regions under cropland and pasture.
Soil Use and Management - Tập 34 Số 2 - Trang 187-196 - 2018
Multi‐objective optimization for diffuse pollution control at zero cost Abstract Agricultural best management practices (BMP s) are gaining ground as a means of mitigating diffuse nutrient pollution of surface waters in agricultural catchments; however, their cost‐effectiveness depends on the location‐specific characteristics of the land on which they are applied. To identify acceptable catchment management solutions with respect to environmental and economic objectives, a decision support tool (DST ) is used in this study. The DST integrates the river basin soil and water assessment tool (SWAT ) model that serves as the nonpoint source pollution estimator into an optimization framework consisting of a multi‐objective genetic algorithm that searches for optimal selection and location of BMP s in the landscape. A three‐objective optimization problem has been previously solved for the A rachtos catchment in western Greece including the implementation costs of several types of BMP s such as nutrient application, crop, soil and livestock management and total annual diffuse losses of total phosphorus (TP ) and nitrate‐nitrogen (NO 3 ‐N ) from land to surface waters. In the present study, a solution of negligible total cost for the whole catchment was selected from optimal two‐dimensional trade‐off curves of cost‐TP and cost‐NO 3 ‐N , aiming to complement previously analysed management options and further enhance decision‐making in this catchment. The zero cost solution led to 30 and 20% reductions in TP and NO 3 ‐N river concentrations, respectively, corresponding to contour cultivation without tillage in corn, fertilizer management in alfalfa as well as livestock and manure management along with the establishment of filter strips at the edge of some corn and pastureland fields. The proposed methodology enabled the identification of a low cost, and possibly more favourable, compared to previous findings, combination of BMP s that ensures good quality of river water. It helps to provide the basis for sustainable land‐use planning and management in large agricultural landscapes, thus aiding decision‐making and cost‐effective implementation of E nvironmental D irectives.
Soil Use and Management - Tập 29 Số s1 - Trang 83-93 - 2013
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