Soils, woody plants and farm-household wealth: Context-specific links in Southern Africa

Abstract

In Southern Africa, agriculture is the primary income source for many people. However, smallholder farmers face challenges with low soil fertility and demanding field management. Soil fertility is determined by inherent soil properties as well as by field management, specifically vegetation and soil management. Management requires economic resources and thus varies with farm-household wealth. Wealthier farmers may have preferential access to high-quality agricultural land, which can confound the relationship between soil quality and wealth. The main objective of this study was to analyse the relationship between household wealth and socio-economic factors, soil quality and smallholder farmers' field management in two different agricultural policy contexts in Southern Africa. Our hypothesis was that farm household wealth is linked to better soil quality and field management. The study was undertaken in the Western Province of Zambia and the Zambezi Region of Namibia, analyzing the economic backgrounds and field management practices of 90 farmers based on data from household surveys across different wealth classes (low, intermediate, high). Field-based ecological studies were conducted on the croplands of the selected farmers, investigating woody plants, and soil properties, including texture, soil organic carbon, and cation exchange capacity. In Zambia, homogeneity of inherent soil properties limits disparities in land distribution and soil quality across wealth classes. Higher yields among relatively wealthy farmers were primarily attributable to soil fertility management rather than differences in inherent soil quality. However, these management practices did not improve soil fertility. In Namibia, soil heterogeneity was linked to unequal land distribution, with the wealthier households farming on inherently better soils with higher clay, silt, and organic carbon contents. However, these farm-households invested less in field management; consequently, higher soil fertility did not result in higher yields. Among wealthy farm-households, off-farm income opportunities decouple agricultural productivity from land quality by reducing field management efforts. Farm-household wealth does not universally correlate with better soil quality or yields in our study area, as off-farm income decouples management from productivity. Wealthier farmers have better inherent soils, indicating preferential access to agronomically suitable land. The findings highlight the need for context-specific agricultural strategies that consider both socio-economic and biophysical factors for sustainable agricultural production. In contexts characterised by heterogenous soil quality, disparities in farm-household wealth can produce inequalities in land quality distribution. Land reform and allocation policies must account for this relationship to reduce the risk of soil-quality-induced poverty traps. Interactions between household wealth, soils, and field management in smallholder farming systems in Zambia and Namibia: The figure contrasts Zambia (top panels) and Namibia (low panels) in terms of soil texture, soil organic carbon (SOC), field management, woody plants and maize yields across three wealth classes (Low, Intermediate, High). In Zambia, wealthier households invest more in field management, resulting in higher yields despite similar soil conditions. In Namibia, wealthier farmers farm better soils, but invest less in management, resulting in no yield benefit. • Wealth-Soil-Management dynamics vary by country context. • Natural soil heterogeneity shapes inequalities in land access. • Soil fertility management drives yields in homogeneous soil landscapes. • Off-farm income weakens agricultural investments.