A self-regulating, low-energy, clay-based irrigation system : performance assessment in moringa and cowpea

Abstract

Crop failures are common in rain-fed farming in sub-Saharan Africa, especially in water-scarce South Africa. Inadequate rainfall necessitates innovative solutions to enhance food production. Water-saving irrigation technologies can significantly reduce crop failures, particularly for smallholder farms with limited access to irrigation water. This study evaluated the effects of Self-Regulating, Low-Energy, Clay-Based Irrigation System (SLECI), subsurface (SDI) and surface drip (DI) on the performance of moringa (Moringa oleifera) and cowpea (Vigna unguiculata), cultivated either as mono (sole) crops or in intercropping systems, in an open experimental field in South Africa. The experimental design was a factorial Randomized Complete Block Design (RCBD) replicated three times. The main aim was to assess water productivity and yield performance in different irrigation systems over two growing seasons. The results showed that the SLECI irrigation system was more suitable for M. oleifera, while V. unguiculata performed best with standard drip irrigation. Moringa oleifera fresh leaf biomass was higher under SLECI with sand around the clay element and surface drip irrigation with 1.42 t/ha, followed by the SLECI treatment without sand with 1.25 t/ha, while the least yield was noted in subsurface drip irrigation treatment with 1.18 t/ha. Vigna unguiculata (a dual-purpose crop for grain and leaves) produced higher total fresh biomass yield under subsurface drip irrigation treatment with 66.26 t/ha, followed by the SLECI treatment without sand (61.51 t/ha), while drip and SLECI with sand showed similar yield with 52.34 and 52.31 t/ha, respectively. In M. oleifera, the irrigation water productivity (IWP) varied from 0.26 kg/m3 below the surface to 0.65 kg/m3 after the SLECI treatment with sand. IWP in V. unguiculata treatments ranged from 27.52 kg/m3 in SLECI without sand to 9.52 kg/m3 under surface drip irrigation. In addition, chlorophyll content and stem diameter were elevated under SLECI, reflecting enhanced nutrient and water availability. The findings have important implications for sustainable agriculture under water-limited conditions.