Climate-smart agriculture options on coarse-textured soils for improved food security in semi-arid areas: climate change awareness and adaptation, sub-surface water retention, plant density and nutrient managem

Rainfed maize production by smallholder farmers is at risk due to climate change, exacerbated by low soil moisture and poor fertility in sandy soils under semi-arid conditions. This thesis assessed climate-smart agriculture (CSA) options to deal with the risks. A survey was conducted in Zimbabwe to assess farmers’ awareness of extreme weather events, their adaptation strategies and associated maize yield. On-farm experiments evaluated CSA options for management of soil water, nutrients and crop density. All 245 farmers interviewed reported awareness and experience of extreme weather events such as drought, flooding and temperature changes. However, despite a range of reported adaptation strategies, reported maize yield averaged only 0.6 t ha-1. Integrating sub-surface water retention technology (SWRT) with different maize densities or soil amendments improved maize productivity to different degrees in dry (305-352 mm) and wet (424-780 mm) seasons. Use of SWRT increased maize grain by 21-24% and total biomass yield by 13-22%, and showed potential to increase maize rainwater use efficiency (RWUE) over four years. Plant density increased from 37,000 to 43,000 plants ha-1 gave optimal four-year average maize grain yield (2.7 t ha-1), and RWUE (5.5 kg ha-1 mm-1). Combining organic and inorganic soil amendments gave 2.3-3.4 t ha-1 grain yield as a three-year average. Average maize yield ranged between 0.3-1.4 t ha-1 in dry seasons and 3-5.5 t ha-1 in wet seasons. In conclusion, management of crop density, soil water and nutrients in smallholder farming increased maize productivity to varying degrees due to seasonal variations in rainfall patterns.