Improving fertilizer recommendations for farmers is essential to increase food security in smallholder landscapes. Currently, blanket recommendations are provided across agro-ecological zones, although fertilizer response and nutrient use efficiency by maize crop are spatially variable. We aimed to identify factors that could help to refine fertilizer recommendation by analyzing the variability in fertilizer response (FR) and the agronomic nitrogen use efficiency (N-AE). A literature search for on-farm studies across Kenya and Sub-Sahara Africa (SSA), excluding Kenya, yielded 71 publications. The variability in FR was studied using a meta-analysis whereas key factors that influence FR and N-AE were studied with linear regression models. On average, the FR was 2, but it varied considerably from 1 to 28.5 (excluding outliers). In SSA, 18% of the plots were non-responsive plots with an FR < 1. The main factors affecting N-AE for Kenya were P-Olsen, silt content, soil pH, clay and rainfall, whereas only soil pH, exchangeable K and texture were important for SSA. However, our study indicates that available data on soil, climate and management factors could explain only a small part (< 33%) of the variation in FR and N-AE. Soil pH, P-Olsen, silt content, and rainfall had significant but low levels of power in explaining variation in FR and N-AE. Our findings indicate that strategies to refine fertilizer recommendation should include information on soil types and soil properties.
Tag: fertilizer application
Phosphorus management in tropical agroforestry: current knowledge and research challenges
Impacts of Grinding and Acidification of Animal Bones with Coffee Wastewater on Plant Dry Matter Yield and Recovery of Phosphorus
In sub-Saharan Africa, soil fertility depletion and limited access to mineral phosphorus (P) fertilizers are considered among the main constraints of crop productivity. The goal of our work is to make P fertilizer from locally available materials, thus reducing the costs due to importation and transportation for smallholder-farmers with limited financial capacities. Cattle bones collected from slaughterhouses were ground to two fineness-level, acidified using coffee wastewater (pH ~4.3), and then compared to commercially available diammonium phosphate (DAP) in a pot experiment using Zea mays (maize) and Phaseolus vulgaris (common bean). Finely ground bones increased maize and common bean dry matter yield (DMY) and P uptake compared to coarsely ground bones, but a significant interaction between grinding and acidification also suggests that acidification with coffee wastewater increased availability of bone-based P, at least two-times more DMY and P uptake under acidified finely ground bones than for non-acidified treatments. In addition, acidified finely-ground bones produced maize and common bean DMY, P uptake and P recovery efficiency that were comparable to those of DAP. These results demonstrate the utility of acidified finely ground bones to enhance crop yields, potentially serving as an alternative P-rich resource to imported and expensive fertilizers that depend on nonrenewable resources. © 2021 Taylor & Francis Group, LLC.
Use and benefits of tree germplasm from the World Agroforestry genebank for smallholder farmers in Kenya
The World Agroforestry (ICRAF) in Kenya plays a key role in conserving tree genetic diversity, thereby contributing to the delivery of ecosystem services in tree-based production systems. This study explored the benefits of using the two most popular fodder tree species among smallholder farmers, sourced from the ICRAF genebank: Calliandra calothyrsus (Calliandra) and Gliricidia sepium (Gliricidia). Through a survey of key informants and genebank users, we examined the benefits derived from the adoption of Calliandra and Gliricidia and the unique role of the ICRAF genebank as the main source of tree germplasm for Kenyan smallholders. The constraints to germplasm access could limit protein fodder supply and the intensity of fertilization in farmers’ fields, which in turn could affect productivity in livestock and maize sectors in Kenya. We find that improved food security, higher incomes, increased milk production, reduced vulnerability to drought, reduced soil erosion, and enhanced soil fertility are identified as the main farmer-perceived benefits linked to the use of Calliandra and Gliricidia. The findings demonstrate the importance of agroforestry in the delivery of ecosystem services, in the light of climate change and heightened pressure for sustainable agricultural practices, and the crucial role of the genebank in conserving and distributing unique, high quality tree germplasm.