Diagnostic trials: a field guide

The Diagnostic Trials, conducted in Kenya, Malawi, Mali, Nigeria, and Tanzania, constitute a major part of Africa Soil Information Service agronomic activities. This guide provides a standard tool that is part of a structured approach for the diagnosis of soil health related constraints to crop production. It is intended for use by national and international agricultural research systems, development partners and extension services to ensure standard procedures in data collection that will feed to an Africa-wide database of diagnostic trials, allowing an increase in data density over time and an improvement of the reliability in the assessment of soil constraints and inferences

Profitability of diammonium phosphate use in bush and climbing bean-maize rotations in smallholder farms of Central Burundi

Article purchasedSoil fertility decline is a major constraint to bean (Phaseolus vulgaris L.) and maize (Zea mays) production in the Central Highlands of Burundi. Nutrient sources, specifically fertilizers, are paramount to increasing the production in the regions. Hence, improving fertilizer use efficiency is considered as a key factor towards sustainable intensification. The use of grain legumes with low harvest indices, such as climbing beans, are assumed to improve soil fertility and fertilizer use efficiency. This study compares the rotational effects of bush and climbing bean varieties on maize and evaluates the profitability of diammonium phosphate (DAP, 18–46-0) fertilizer in the bean-maize rotations in 59 smallholder farms of Mutaho district, Gitega Province in Central Burundi. The application of DAP fertilizer significantly increased the grain yields by 14% and 21% for bush and climbing beans, respectively (P 2 $$−1) in a climbing bean-maize rotation while 45% of the farmers in a bush bean-maize rotation. Regression tree analysis showed that targeting fertilizer use to soils with higher C and clay content, and ensuring timely planting are the predominant factors to ensure fertilizer response and profitable returns. This study confirms the need for integrated soil fertility management (ISFM), and that a combination of judicious fertilizer use, an improved grain legume (climbing bean) and adjustment to local conditions (targeting to responsive soils) maximizes economic returns of legume-cereal rotation systems

Maize response to macronutrients and potential for profitability in sub-Saharan Africa

The final publication is available at Springer via http://dx.doi.org/10.1007/s10705-015-9717-2Sub-Saharan Africa (SSA) is plagued by low productivity and little research is available on the attainable responses and profitability to applied nutrients under variable environments. The objective of this study was to determine the attainable maize grain response to and potential of profitability of N, P and K application in SSA using boundary line approaches. Data from experiments conducted in SSA under AfSIS project (2009–2012) and from FAO trials database (1969–1996) in 15 countries and constituting over 375 different experimental locations and 6600 data points are used. Both response to fertilizer and value cost ratio (VCR) are highly variable and no more than 61 % cases for N, 43 % for P and 25 % for K attain VCR of 2 or more. Also, based on the recent AfSIS data, VCR exceeds 1 in just 67 % (N), 57 % (P) and 40 % (K) of the cases, even when best management practices are applied on a research farm, and interest rates are zero. Chances for profitability are highest when soil organic carbon is 1–2 % and control maize grain yield is 1–3 t ha−1 but also depends on relatively static soil properties (primarily texture and mineralogy) that are not under farmer control. We conclude that return on investment of macronutrient fertilizer is highly variable and can be substantially increased by helping farmers decide where to apply the fertilizers. Consequently, farmers need access to information on factors influencing economic returns of fertilizer use in order to make the right decisions

Legume CHOICE - a participatory tool to fit multi-purpose legumes to appropriate niches in mixed crop-livestock farming systems

German Federal Ministry for Economic Cooperation and DevelopmentDeutsche Gesellschaft für Internationale Zusammenarbei

Soil: the great connector of our lives now and beyond COVID-19

Humanity depends on the existence of healthy soils, both for the production of food and for ensuring a healthy, biodiverse environment, among other functions. COVID-19 is threatening food availability in many places of the world due to the disruption of food chains, lack of workforce, closed borders and national lockdowns. As a consequence, more emphasis is being placed on local food production, which may lead to more intensive cultivation of vulnerable areas and to soil degradation. In order to increase the resilience of populations facing this pandemic and future global crises, transitioning to a paradigm that relies more heavily on local food production on soils that are carefully tended and protected through sustainable management is necessary. To reach this goal, the Intergovernmental Technical Panel on Soils (ITPS) of the Food and Agriculture Organization of the United Nations (FAO) recommends five active strategies: improved access to land, sound land use planning, sustainable soil management, enhanced research, and investments in education and extension

Looking back and moving forward: 50 years of soil and soil fertility management research in sub-Saharan Africa

Article purchased; Published online: 02 Nov 2017Low and declining soil fertility has been recognized for a long time as a major impediment to intensifying agriculture in sub-Saharan Africa (SSA). Consequently, from the inception of international agricultural research, centres operating in SSA have had a research programme focusing on soil and soil fertility management, including the International Institute of Tropical Agriculture (IITA). The scope, content, and approaches of soil and soil fertility management research have changed over the past decades in response to lessons learnt and internal and external drivers and this paper uses IITA as a case study to document and analyse the consequences of strategic decisions taken on technology development, validation, and ultimately uptake by smallholder farmers in SSA. After an initial section describing the external environment within which soil and soil fertility management research is operating, various dimensions of this research area are covered: (i) ‘strategic research’, ‘Research for Development’, partnerships, and balancing acts, (ii) changing role of characterization due to the expansion in geographical scope and shift from soils to farms and livelihoods, (iii) technology development: changes in vision, content, and scale of intervention, (iv) technology validation and delivery to farming communities, and (v) impact and feedback to the technology development and validation process. Each of the above sections follows a chronological approach, covering the last five decades (from the late 1960s till today). The paper ends with a number of lessons learnt which could be considered for future initiatives aiming at developing and delivering improved soil and soil fertility management practices to smallholder farming communities in SSA

Carbon and nitrogen dynamics in a phosphorus deficient soil amended with organic residues and fertilizers in western Kenya

The contribution of organic resources to the restoration of soil fertility in smallholder farming systems in East Africa is being tested as an alternative to costly fertilizers. Organic inputs are expected to have advantages over fertilizers by affecting many biochemical properties controlling nutrient cycling. Our study examined changes in soil C and N, C and N mineralization, microbial biomass C (MBC) and N (MBN), and particulate organic matter (POM) in a P-limiting soil in western Kenya after applications of organic residues and fertilizers to overcome P limitation to crops. Leaf biomass from six different tree (shrub) species was incorporated into the soil at 5 Mg ha−1 for five consecutive maize growing seasons, over 2.5 years. Triple superphosphate was applied separately at 0, 10, 25, 50, and 150 kg P ha−1 in combination with 120 kg N ha−1 as urea. Soil inorganic N, soil organic C, mineralizable N, and total C in all POM fractions and total N in the 53- to 250-μm POM fraction increased following addition of all organic residues compared to the control. Whether there was an advantage of organic residue incorporation over inorganic fertilizer use depended on the soil parameter studied, the organic residue and the rate of fertilization. Most differences were found in N mineralization where 14.4–21.6 mg N kg−1 was mineralized in fertilizer treatments compared to 25.2–30.5 mg N kg−1 in organic residue treatments. C and N mineralization and the 53- to 250-μm POM fractions were the most sensitive parameters, correlating with most of the studied parameters. Organic residues can contribute to improved soil nutrient cycling while the magnitude of their contribution depends on the biochemical properties of the residues

Sulphur immobilization and availability in soils assessed using isotope dillution

Increasing recognition of S deficiency in soils has raised the need for understanding processes governing S cycling and availability in soils. However, the quantification of the two main processes of S cycling, i.e. mineralization and immobilization, remains difficult as these processes occur simultaneously. A modified isotope 35SO4 dilution technique was developed and used to measure the effect of sulphate (SO4) fertilization on S mineralization and immobilization in planted (pot experiment with ryegrass (Lolium multiflorum L.)) and unplanted soils (incubation). The immobilization and mineralization of S was calculated from the dynamics of stable and labelled S in soil KH2PO4 extracts containing an anion exchange membrane that concentrates SO4 and mainly excludes other S species. The mathematical analysis of the isotope dilution data differs from methods proposed earlier. The radiolabile S in unplanted soil (E value) and in ryegrass (L value) were used as a measure of total available S in soils. Sulphate immobilization rate significantly declined during incubation. Sulphate application reduced gross mineralization but surprisingly reduced SO4 immobilization. The E value significantly increased during the incubation in all soils as a result of gross mineralization, e.g. from 3.8 mg S kg−1 at day 0 to 11.5 mg S kg−1 at day 43 in the sandy soil with no sulphate addition. A full recovery in the E value of S added in (+S) treatments was achieved. Similarly, radiolabile S in the above-ground ryegrass biomass (L value) increased with S addition, with a full recovery of added S. The E and L values nearly fit a 1:1 line suggesting identical S dynamics in a planted and unplanted soil. The method proposed has operational advantages compared to methods used earlier

Population density and distance to market does not influence the farmers use of organic manure.

This study developed and employed a socio-economic-ecological-modeling (SEEM) framework in its analyses. The SEEM is made up of four resource use domains of highlow population density and highlow access to market and two agro-ecologies in the savanna of Nigeria. Data used comprises a sample of 320 farm households in northern Nigeria. The pattern of organic manure use varied slightly and insignificantly across agro-ecological and resource use domains. The major finding of the study is that the resource use domains made use of same amount of organic manure. The level of organic manure use is, however, below the recommended levels for the cereal-based production systems in the study area. Policy that encourages the intensity of manure use and crop-livestock integration is recommended to support integrated soil fertility management practices in the study area