Assessment of Farmer-Led Irrigation Development (FLID) in South Africa: A Case Study of Vhembe District

Abstract

Small-scale farming has been identified as a driver of poverty reduction and food security worldwide. However, several issues facing small-scale agriculture are exacerbated by factors such as water scarcity, soil degradation, and climate change. In sub-Saharan Africa, Farmer-led irrigation development (FLID) has emerged as a decentralised pathway for agricultural intensification, particularly in semi-arid regions. Despite its growing popularity and relevance worldwide, farmer-led irrigation development in South Africa remains insufficiently quantified, particularly with respect to its performance determinants and environmental sustainability. Hence, identifying, characterising, and assessing FLID, along with the associated agricultural water and soil management practices, will improve the country's agricultural sector. In this context, this study assessed FLID in South Africa, integrating socio-economic analysis with empirical soil and irrigation water assessments to evaluate farm productivity outcomes, irrigation water quality impacts, and soil sustainability under independent smallholder farms. A mixed-methods design was employed. Structured questionnaires were administered to 66 irrigation farmers across Thulamela and Makhado municipalities to characterise irrigation technologies, water sources, cropping intensity, soil–water management practices, institutional linkages, and income performance. Principal Component Analysis (PCA) identified composite management dimensions, and Multiple Linear Regression (MLR) quantified their influence on farm income. From this survey, eight representative farms were purposively selected for detailed biophysical assessment. Soil samples were collected from cultivated and adjacent uncultivated reference areas at depths of 0–20 cm and 20–40 cm. Undisturbed cores were used to determine bulk density (BD), porosity, and soil water retention curves (SWRC), amongst others, while composite samples were analysed for pH, electrical conductivity (EC), exchangeable bases, sodium adsorption ratio (SAR), nitrate nitrogen, available phosphorus (P), and potassium (K). Irrigation water samples were analysed for EC, SAR, major cations, and nitrate. Statistical analyses included analysis of variance, descriptive statistics, correlation, and regression at p ≤ 0.05 using Minitab version 19.0. for soil and water data, while the Statistical Package for Social Science (SPSS) was used to analyse the questionnaire data. Results show that 63% of farmers relied on boreholes and 62% used drip irrigation, enabling two to three cropping cycles annually. Income performance was significantly associated with integrated soil and water-saving knowledge and irrigation scheduling capacity (P ≤ 0.05), indicating that management intensity rather than farm size determined productivity. However, groundwater dependence introduced measurable chemical risks. Borehole water exhibited a mean electrical conductivity of 737 μS/cm and SAR of 1.09, with 75% of samples exceeding FAO salinity risk thresholds. Irrigation water electrical conductivity was positively correlated with soil sodium adsorption ratio at 0–20 cm (r = 0.753, p = 0.015), while irrigation water sodium adsorption ratio explained 59.81% of the variability in surface soil nitrate nitrogen (R² = 0.598, p = 0.024), demonstrating a statistically significant soil response to irrigation water quality. Concurrently, cultivated soils showed substantial nutrient enrichment relative to reference sites, with available phosphorus increasing by 309%, nitrate nitrogen by 435%, and exchangeable potassium by 73% (P ≤ 0.05), reflecting active fertilisation practices. Mean bulk density was 1.36 g/cm³, and soil water retention curve analysis revealed a mean available water capacity of 0.24 m³/m³, ranging from 0.17 m³/m³ in sandy soils to 0.30 m³/m³ in clay soils. Soil water retention curve (SWRC) analysis revealed a mean available water capacity of 0.24 m³/m³, ranging from 0.17 m³/m³ in loamy sands to 0.30 m³/m³ in clay soils. The greater buffering capacity of clay-rich soils moderated sodium accumulation and moisture stress, highlighting the role of pedological variability in system resilience. Although no severe degradation thresholds were exceeded, the statistically significant soil–water interactions indicate detectable early-stage sodicity development. FLID in Vhembe District, therefore, represents a productive yet environmentally conditional intensification pathway, where long-term sustainability depends on proactive groundwater monitoring, improved soil management, and stronger institutional integration to safeguard soil functionality and smallholder livelihoods in semi-arid South Africa.