On farm testing of integrated nutrient management strategies in Eastern Uganda

This paper reports on a Participatory Learning and Action Research (PLAR) process that was initiated in three villages in eastern Uganda in September 1999 to enable small-scale farmers to reverse nutrient depletion of their soils profitably by increasing their capacity to develop, adapt and use integrated natural resource management strategies. The PLAR process was also used to improve the participatory skills and tools of research and extension personnel to support this process. The farming systems of the area were characterised for socio-economic and biophysical conditions that included social organisations, wealth categories, gender, crop, soil, agro forestry and livestock production. Farmers identified soil fertility constraints, their indicators, and causes of soil fertility decline, and suggested strategies to address the problem of soil fertility decline. Soil fertility management diversity among households indicated that most farmers were not carrying out any improved soil fertility management practices, despite previous research and dissemination in the area. Following the diagnosis stage and exposure visits to other farmer groups working on integrated soil fertility projects, the farmers designed 11 experiments for on-farm testing. One hundred and twenty farmers then chose, for participatory technology development, sub-sets of these 11 experiments, based on the major agricultural constraints and the potential solutions identified and prioritised by the farmers. Quantitative and qualitative results from the testing, farmer evaluation and adaptation, training, dissemination strategies and socio-economic implications of these technologies are discussed

Fertilizer Use Issues for Smallholder Agriculture in Tropical Africa

Fertilizer is an essential input for wide-scale sustainable intensification of crop productivity in tropical Africa, but its use by smallholders is often financially constrained. Four fertilizer use issues are addressed. Smallholders need high net returns from their investments, with acceptable risk, which can be achieved with good crop-nutrient-rate choices made in consideration of the farmer’s financial and agronomic context. Soil acidification, which is affected by crop N supply, is best managed with the use of slightly more acidifying but less costly common N fertilizer, e.g., urea, coupled with lime use compared with the use of more costly but less acidifying N fertilizer such as calcium ammonium nitrate. This chapter addresses the feasibility of tailored fertilizer blends for maximizing farmer profit with respect to the nutrient supply cost, the need for flexibility in nutrient application according to the farmer’s context, and the weak justification for tailoring blends based on soil test results. The use of a well-formulated blends is justified in some cases, e.g., for some crops in Rwanda, but the supply of blends does not justify restricting the supply of common fertilizers. Farmers need to be aware that unregulated nontraditional products very often fail to provide the claimed benefits. Fertilizer use, sometimes with timely lime application, can be highly profitable with modest risk with good crop-nutrient-rate choices, adequate free-market fertilizer supply, and avoiding products with unsubstantiated claims

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

Bringing Climate Smart Agriculture to Scale: Experiences from the Water Productivity Project in East and Central Africa

Since 2010, six research organizations in the region have implemented a regional project that sought to combat food insecurity, poverty and climate change by up-scaling Climate-Smart Agriculture (CSA) technologies across farms and landscapes using the Climate Smart Landscape (CSL) approach. Several CSA technologies were evaluated and promoted across landscapes using this approach with remarkable success. Maize yields in Kenya rose from 0.5 to 3.2 t ha-1, resulting in over 90% of the watershed communities being food secure. In Madagascar, rice yields increased from 2 to 4 t ha-1 whilst onion yields increased from 10 to 25 t ha-1, resulting in watershed communities being 60% food-secure. In Eritrea, sorghum yields increased from 0.6 to 2 t ha-1. Farmers in Ethiopia earned US$10,749 from the sale of pasture whilst in Madagascar, watershed communities earned additional income of about US$2500/ha/year from the sale of onions and potatoes during off-season. Adoption levels of various CSA technologies rose from less than 30% to over 100% across the participating countries, resulting in rehabilitation of huge tracts of degraded land. In a nutshell, the potential for CSL in the region is huge and if exploited could significantly improve our economies, lives and environment

THE EFFECT OF TIME ON PHOSPHORUS AVAILABILITY ON TWO SOILS AS DETERMINED BY SOIL ANALYSIS AND PLANT UPTAKE

Laboratory analysis and greenhouse experiments were conducted to investigate if standard soil tests for P adequately evaluate the availability of applied fertilizer, the nature and availability of residual P, and evaluation of the applicability of Langmuir and Freundlich adsorption equations in describing P sorption by a calcareous Uly silt loam subsoil and an acidic Thurman loamy fine sand topsoil. Monopotassium phosphate (KH(,2)PO(,4)) at 0, 10, 20, 40, and 80 mg P kg(\u27-1)was mixed with soils and incubated at field capacity for 20 months. Phosphorus was extracted with Bray P-1, NaHCO(,3), Mehlich No. 2, North Carolina, and Truog\u27s extractants. Oats (Avena sativa) were grown on the soils after 4, 8, and 20 months. The A and L values were also determined using (\u2732)p. Highly significant (P \u3c 0.01) regression coefficients were obtained between extractable P with A and L values. The results suggest that Bray P-1, NaHCO(,3), and Mehlich No. 2 extractants were better indicators of plant available P as compared to North Carolina and Truog extractants. However, it was apparent that as soils were fertilized with P. all three extractants underestimated plant available P. Maximum dry matter yield and total P uptake was obtained at \u3e40 mg P kg(\u27-1). Generally, there was a decrease in extractable P with time using the five soil tests in both soils. However, there was high correlation (r \u3e 0.88) among amounts of Bray P-1, NaHCO(,3), and Mehlich No. 2 extracted phosphorus. The phosphate potential studies indicated that fertilizer reaction products are P rate dependent. Uly soil was undersaturated with octocalcium phosphate (OCP) \u3c20 mg P kg(\u27-1), whereas the soil was at equilibrium or OCP was precipitated at \u3e40 mg P kg(\u27-1). The pH and phosphate potentials suggest amorphous Al-P and Fe-P were the dominant reaction products in Thurman soil. The sorption data indicated two adsorption surfaces in Uly soil and one adsorption surface in Thurman soil