Maize yield stability under organic and conventional farming systems in sub-humid agro-ecozones of Central Kenya

Summary

Maize (Zea mays L.) is the main staple crop and is important to the food security and livelihoods of people globally. We evaluated the effects of organic and conventional farming systems on maize grain yield and temporal yield stability under different external input levels in a long-term experiment (2007–2022) at two sites in Kenya. We implemented four farming systems: organic high (Org-High), conventional high (Conv-High), organic low (Org-Low), and conventional low (Conv-Low) in a randomized complete block design. Growth indicators for maize, height, stem diameter, and grain yield were higher in high input systems, but grain yield stability was not. At the onset of the experiments, grain yields of conventional systems were higher compared to the organic systems, whose yield levels gradually increased over time, reaching the yield levels of conventional systems. With regard to grain yield stability, the site (Chuka) with better soil fertility, the Conv-High system had the least residual variance (0.28 Mg ha−2), followed by Org-Low, Conv-Low, and Org-High showing the highest residual variance (0.67 Mg ha−2). Contrary, in the site (Kandara) with low soil fertility, Org-Low had the lowest residual variance in grain yield (0.16 Mg ha−2), followed by Conv-Low and Org-High, while Conv-High (4.15 Mg ha−2) had the highest residual variance. We observed that applying higher nutrient input levels did not necessarily lead to yield stability. Our findings suggest promoting long-term implementation of organic farming practices, especially in regions with degraded soils, for improved yield and resilience.