Modelling of Cowpea Response to Varying Irrigation and SAP Levels Under Greenhouse Conditions Using AquaCrop

Irrigation water management is key to promoting resilient crop production amidst the increasing effects of climate change. Super absorbent polymer (SAP) is an innovative technology for conserving irrigation water within arid and semi-arid lands (ASALs). AquaCrop, a water productivity model, has been used for irrigation water management. This study aimed to model the response of cowpea to various irrigation and SAP levels under greenhouse conditions via AquaCrop. The experiments included five SAP application rates [0% (control), 0.05%, 0.1%, 0.15% and 0.2% to weight of the soil substrate] and five irrigation levels [full irrigation (FI), and 80%, 70%, 60% and 30% FI]. The AquaCrop model simulations matched the observed values with a normalized root mean square error of less than 16%. The simulated yield and biomass for full irrigation and 0% SAP were 5.1 and 11.0 t/ha, respectively, whereas the observed values were 5.3 and 10.8 t/ha, respectively. Treatments with SAP showed increased yield, biomass, water productivity (WP_ET) and harvest index (HI) with increased water stress up to 137%, 17%, 10% and 117%, respectively. Thus, SAP can improve crop production, and the AquaCrop model is suitable for improving irrigation water productivity within ASALs where water is scarce.