When yield gaps are poverty traps: The paradigm of ecological intensification in African smallholder agriculture

TLDR

Yield gaps are widespread across African smallholder farms, largely driven by poor soil fertility and limited nutrient availability. The study aims to define two key yield gaps—between actual yields and water‑limited potential, and between actual yields and locally attainable yields—and to examine the ecological intensification paradigm for African agriculture. The authors estimate these gaps for major crops and present a practical framework for calculating yield gaps across diverse farming systems. The analysis shows that smallholder farmers cannot reap gains from genetic improvement because continued cropping without adequate nutrients and organic matter degrades soils, creating a chronic poverty trap that calls for a policy rethink to improve productivity and food security.

Abstract

Yield gaps are pervasive in African smallholder agriculture, and are large for almost all crops in all regions. There is consensus that poor soil fertility and nutrient availability are the major biophysical limitations to agricultural production in the continent. We identify two major yield gaps: (1) the gap between actual yields (YA) and the water-limited yield potential (Yw), which is the maximum yield achievable under rainfed conditions without irrigation if soil water capture and storage is optimal and nutrient constraints are released, and (2) The gap between YA, and a locally attainable yield (YL) which corresponds to the water and nutrient-limited yields that can be measured in the most productive fields of resource endowed farmers in a community. Estimates of these two yield gaps are given for major crops, together with a framework for how yield gaps can be estimated in a pragmatic way for different farming systems. The paradigm of ecological intensification which focuses on yield potential, soil quality and precision agriculture is explored for the African context. Our analysis suggests that smallholder farmers are unable to benefit from the current yield gains offered by plant genetic improvement. In particular, continued cropping without sufficient inputs of nutrients and organic matter leads to localised but extensive soil degradation and renders many soils in a non-responsive state. The lack of immediate response to increased inputs of fertiliser and labour in such soils constitutes a chronic poverty trap for many smallholder farmers in Africa. This necessitates a rethink for development policy aimed to improve productivity and address problems of food insecurity.