Browsing by Author "Fonte Steven J."

Now showing 1 - 3 of 3
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    A Soil Tool Kit to Evaluate Soil Properties and Monitor Soil Health Changes in Smallholder Farming Contexts
    (Elsevier Publishing Company, 2020-10-15) Nyamasoka-Magonziwa Blessing; Vanek Steven J.; Ojiem John O.; Fonte Steven J.
    Smallholder farmers often face challenges in managing soil fertility due to limited inputs and high spatial variability on their farms. While improved knowledge of soil constraints could help them manage limited resources more effectively, formal soil analyses are typically out of reach due to high costs of testing and transport associated with regional analytical laboratories. To address these challenges, we assembled a tool kit that uses minimal reagents and low-cost equipment to provide in-field quantitative data that are comparable to formal laboratory methods. We validated our tool kit measurements against standard analyses conducted at national laboratories on soils collected from 36 smallholder farms in Kenya and 115 farms in Peru. Additionally, in Kenya, we evaluated two legume treatments, involving the incorporation of residues from: 1) Lablab purpureus (lablab), versus 2) Phaseolus vulgaris (common bean). The tool kit measurements that were considered include important indicators of soil health (such as permanganate oxidizable carbon (POXC), available P, pH, particulate organic matter (POM), and aggregate stability) that can influence crop yields and multiple soil functions. POXC and pH measured with the tool kit from Kenyan soils were highly correlated to those measured by a standard laboratory (R2 = 0.77; R2 = 0.56; respectively). The tool kit and standard laboratory available P were less well correlated, but also showed a highly significant positive relationship (R2 = 0.30). Similar patterns were noted for POXC, pH and available P measured in Peruvian soils (R2 = 0.75; R2 = 0.75; R2 = 0.35; respectively). Importantly, the tool kit and standard lab analyses also displayed similar abilities to predict maize grain yield in Kenya. When used to detect soil impacts of incorporating P. vulgaris versus L. purpureus, only POM differed significantly between the two legume treatments, although L. purpureus was slightly higher for most of the beneficial soil health properties. Our findings suggest that the tool kit methods proposed here have broad applicability to smallholder farms for explaining variability in crop yields, assessing soil contexts, and quantifying management-induced changes in soil health.
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    Examining the Contributions of Maize Shoots, Roots, and Farming Manure to Stable Soil Organic 2 Carbon Pools in Tropical Smallholder
    (Elsevier B.V, 2022) Nyamasoka-Magonziwa Blessing; Vanek Steven J.; Ojiem John O.; Fonte Steven J.
    Continuous inputs of organic matter are vital for sustaining soil organic carbon (SOC) and productivity of soils in smallholder crop-livestock systems. However, the dynamics of the different inputs i.e. maize shoots, roots and manure used are poorly understood. Along with organic inputs, use of mineral fertilizers can alter the nutrient stoichiometry of organic matter inputs and have implications for SOC turnover. This study sought to understand how maize-based inputs and alterations to nutrient stoichiometry contribute to stable SOC pools. We hypothesized that higher quality litter (i.e., manure) contributes more than maize residues to stable SOC pools and that N, P and S additions, designed to balance the stoichiometry of inputs to reflect the stable fine fraction of soil organic matter (C:N:P:S-10,000:833:200:143) results in greater SOC stabilization. We used a 13C natural abundance approach, where the C4 maize residues were incubated for 11 months to trace C stabilization into different SOC pools within a C3 soil. Contrary to our expectations,we observed greater recovery and stabilization of shoot-derived C (2 X more than manure and 1.63 X more than roots) in the mineral-associated organic matter (MAOM) fraction. Mineral N, P and S additions reduced new C recovery in MAOM by 40% compared to no mineral nutrient’s additions. Our study highlights the importance of residue retention as a strategy to maintain SOC and soil health in smallholder systems, and our results challenge the idea that nutrient additions increase C stabilization of added residues.
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    Organic Nutrient Source Allocation and Use in Smallholder Farming Communities: What Are We Missing?
    (Frontiers in Sustainable Food Systems, 2021-08-25) Nyamasoka-Magonziwa Blessing; Vanek Steven J.; Carolan Michael; Ojiem John O.; Fonte Steven J.
    Organic nutrient sources (ONS) are managed as a key resource by smallholder farmers to maintain the productivity of soils. Recycling of ONS by applying them to soils is a globally dominant strategy of ecological nutrient management. Understanding how ONS produced on-farm are allocated and what drives farmer decision making around their use is critical for sustainable nutrient management in smallholder agroecosystems. Using focus group discussions and a survey of 184 farming households, we studied socio-economic, socio-cultural, and environmental drivers of ONS allocation and use at the farm scale in three contrasting agroecological zones of western Kenya. Farm typologies of ONS management were also developed using cluster analysis based on resource endowment and the connectedness of farmers, management norms, and interaction with extension. Our findings suggest that the more resource endowed a farmer is, the more ONS are allocated to the main plot within the farm. We also observed that farmers preferred allocating more resources to plots that were considered more fertile. Land tenure had an important influence, in that main plots not owned by farmers were more likely to retain ONS such as crop residues. Management of residues is dependent on farmer gender, for instance, female farmers tended to burn legume residues in particular, which is notable since these higher quality residues are often considered key to sustainable soil nutrient management. Farm typologies featured different allocation patterns of ONS and were associated with resource endowment and farmer networks, including external ties to extension agents and internal ties to other farmers. Finally, there was a strong overarching influence of agroecological zone that often escapes characterization on the allocation of ONS. As research and development organizations continue to engage with smallholder farmers to reduce the burden of global food insecurity, the insights gained by this research will allow better anticipation of drivers and obstacles to improved nutrient management in these farming landscapes and communities