Organic farming with smallholder input rates cannot close the yield gap in Central Kenya

Compared to the rest of the world, crop production by smallholder farmers in sub-Saharan Africa shows sizeable yield gaps to the attainable yield. Organic farming is offered as one solution due to its positive impact on human and environmental health, but it is also questioned for its suitability to improve yield substantially. However, data on the comparative performance of organic systems under smallholder agriculture practices is scarce in the developing world. Our study addresses this critical aspect of crop production in sub-Saharan Africa. We investigated annual crop productivity under organic and conventional farming systems using smallholder nutrient application rates in two long-term systems comparison trials in the Central Highlands of Kenya. They involved a three-year crop rotation of maize, leafy vegetables, legumes, and potatoes, repeated five times since its establishment in 2007. Our results show that crop yields in conventional and organic farming systems were generally lower than achievable yields. The yield gap to the attainable yield was neither closed under the organic nor conventional systems. In addition, crop yield under organic was usually lower than in conventional systems. The low yields and yield gap resulted from the limited nutrients, high pest and disease pressure, and dependence on the declining and varying rainfall amounts. Our study highlights the need to improve input rates and, thus, the productivity of smallholder farmers as a key component in reducing poverty and increasing food security.