REGSOMMICS

Background

Low maize yields in sub-Saharan Africa are often the result of poor soil fertility and pose a challenge to local food security. Although maize monocultures are common in Kenya, it has been shown that such systems often lose soil fertility over time, even when they receive high levels of external organic resources and fertilizer inputs. A potential solution for regenerating soil fertility and increasing soil organic matter is to stimulate root inputs, for example by incorporating root-intensive forages and N-fixing legumes. However, the main processes that facilitate soil organic matter formation, the trade-offs between soil organic matter formation and crop yield, and the role of nutrient limitation in agroecosystem regeneration remain poorly understood in tropical agroecosystems. In this project, we address these issues by studying four long-term trials in Kenya, representing four different pedoclimatic conditions, that were redesigned using regenerative system approaches. Based on the former treatments before the redesign, the trials represent different levels of soil degradation which will be used to study the effectiveness of maize-legume rotation, maize-legume intercropping and maize-forage grass relay in building up soil organic matter and increasing yield. The role of external inputs will be tested by dividing the system treatments into those receiving either farmyard manure or green manure of Tithonia Diversifolia, with or without mineral N fertilizer, and those receiving no external inputs.