Validation of AquaCrop Model for Simulated Climate Change Strategies for Maize Production in a Kenyan Nitisol

Abstract

Climate models predict temperature increases of between 3-4o C in Africa by the end of the 21st Century; roughly 1.5oC higher than the global mean. AQUACROP model was validated to compare climate adaptation measures of irrigation, fertility and planting dates using maize crop. Data was collected in the two seasons of 2012 at Kabete in the Upper Midland agro-zone of Kenya from Climate Analogue Location in East and Southern Africa (CALESA) project. Long-term monthly rainfall, minimum and maximum temperatures data from Kabete Meteorological Station were used to determine trends while additional parameters were used to compute other model parameters. A scenario of 10% decline in rainfall and 3oC temperature increase led to at least 6 and 12% enhanced of biomass and yields respectively. Late planted crop suffered 0.3% reduction in canopy cover (CC), and 7.5% reduced transpiration hence 0.2% biomass. This probably resulted from disuse of initial moisture availability and nitrogen flush usually at rainfall onset. Application of 20 kg/ha of N enhanced transpiration hence biomass and especially grain yields by 24.7%. However, while 40kg/ha of N enhanced canopy cover, this did not lead to increased biomass and/or yields. It is purposeless to irrigate when rains are adequate since this only delays harvest index but does not enhance biomass or yields. Late planting is not recommended since the crop would suffer reduced transpiration, CC and biomass. It is needless to continusly enhance fertility levels beyond 20 kg/ha for maize at Kabete.