Evaluating hydrogel amendment rates as a climate-smart strategy for cowpea production under moderate drought in semi-arid Zimbabwe

Abstract

Superabsorbent hydrogels (SAPs) are three-dimensional polymer networks capable of absorbing hundreds of times their weight in water and gradually releasing it to plant roots as soil dries. This property buffers moisture fluctuations, reduces percolation losses, and extends water availability between rainfall events, positioning SAPs as climate-smart amendments for mitigating drought stress in rainfed agriculture. In semi-arid regions such as Zimbabwe, erratic rainfall and mid-season dry spells increasingly constrain crop productivity, underscoring the need for soil amendments that enhance water retention. This study evaluated hydrogel incorporation (0, 0.1, 0.2, 0.3, and 0.4 g/kg soil) under two moisture regimes—well-watered (75–85% field capacity) and moderate drought (45–55%)—on phenology, reproductive traits, and yield of cowpea in a randomized complete block design with three replicates. Hydrogel application progressively delayed flowering (up to 4.4 days) and maturity (up to 5.2 days), while increasing seeds per pod from 10.4 (control) to 13.2 (0.4 g). Moderate drought increased 100 seed weight (19.80 g vs. 14.67 g), partially compensating for reduced seed number. Shelling percentage exhibited a significant hydrogel × moisture interaction (p = 0.026). Most notably, seed yield per plant rose by 41% at the highest hydrogel rate, and the main effect of moisture regime on yield was not significant (p = 0.314), indicating hydrogel fully offset drought penalties. Hydrogel × moisture interactions were largely non-significant, suggesting additive benefits. Overall, superabsorbent hydrogels at 0.4 g/kg of soil represent an effective, climate-smart amendment for enhancing cowpea productivity and buffering against moderate water deficits in semi-arid environments.