Comparative effect of different irrigation levels and soil amendments on cabbage productivity in semi-arid Central Namibia

In semi-arid Central Namibia, poor sandy soils limit sustainable crop production. We assessed cabbage performance in two split-plot field experiments. In Experiment 1, treatments comprised two irrigation levels: full irrigation (watered 3 days a week) and reduced irrigation (watered 2 days a week) as the main plot factor and six soil amendments (biochar; compost; zeolite; nitrogen, phosphorus potassium [NPK]; Be-Grow boost [L] hydrogel; and hoof and horn + bone [HHB] meal) as subplot factors in three replications. Full irrigation produced a significantly higher yield (21.1 t ha⁻¹), head weight (0.958 kg) and larger head girths (42.1 cm). Biochar produced the highest marketable heads (24,884 heads ha⁻¹), water use efficiency (76.0 kg ha⁻¹ mm⁻¹) and the largest head girths (42.7 cm). In Experiment 2, water was applied 5 and 4 days a week for full and reduced irrigation; the application rates of compost, HHB meal, Be-Grow boost (L) hydrogel and NPK were modified. The interaction of Be-Grow boost (L) hydrogel, NPK and biochar with full irrigation and HHB meal with reduced irrigation produced more marketable heads (28,935, 28,009, 27,546 and 28,703 heads ha⁻¹, respectively). Therefore, full irrigation with these amendments could be used for resilient cabbage production in Central Namibia.