What Drives or Constrains Legume Production in Semi-Arid Smallholder Systems? Unpacking Socio-Economic Determinants, Yield Variability, and Decadal Trends in Mkalama District, Tanzania

Abstract

Despite the recognized nutritional, agronomic, and economic roles of grain legumes in sub-Saharan Africa, smallholder yields in semi-arid regions remain persistently low and unstable, with limited empirical understanding of the underlying socio-economic drivers. This study investigated the levels, variability, and ten-year production trends of legumes among smallholder farmers in Mkalama District, Tanzania, and systematically examined the influence of key socio-economic factors on output. A cross-sectional survey of 138 legume-growing households was conducted using structured questionnaires, and data were analyzed using descriptive statistics, one-way ANOVA, and chi-square tests. Results revealed a mean total legume production of 784.52 kg per farmer (SD = 1489.35 kg), indicating extreme variability. Beans dominated as the primary crop (84.06% of farmers), while groundnuts and green gram each accounted for one-third. Over the past decade, production trends were highly unstable: 48.55% of farmers reported fluctuating yields, 35.51% reported declines, and only 2.90% reported increases. One-way ANOVA demonstrated that annual income and farm size significantly influenced legume output (p < 0.001). Farmers earning above 2,000,000 TZS produced on average 2678.08 kg compared to 234.13 kg for those earning below 200,000 TZS. Similarly, farmers with >6 acres produced 1477.35 kg, more than five times the output of those with 1–3 acres. In contrast, education level showed no significant effect on production, and chi-square tests found no significant associations between demographic variables (sex, education, income) and production trends (p > 0.90). These findings provide two key contributions: empirically, they demonstrate that resource endowments, not demographic characteristics, are the primary drivers of legume productivity in semi-arid smallholder systems; and for policy, they highlight the ineffectiveness of undifferentiated demographic targeting. We recommend prioritized interventions in climate-resilient technologies, equitable input subsidies, market linkages, and support for resource-poor farmers to reduce yield variability and stabilize legume production in semi-arid zones.