C. C. Kapkwang, E. C. Kipkorir, D. Raes
Abstract: Water virtually and across the world is a dynamic limited resource and the dramatic increasing population mainly in developing countries requires significant increase in food production. Inadequate water utilization in arid and semi-arid regions are used to improve crop water productivity. Irrigation optimization strategy at field level considers scheduling parameters, when and how much to apply, for each water application is viable. Optimizing control and scheduling parameters in irrigation is one major interconnected problems. The study conducted at Eldume irrigation scheme, Kenya sought to highlight the application of AquaCrop model to simulate crop water productivity of maize crop in arid and semi arid climatic condition. AquaCrop model focuses on water productivity values normalized for atmospheric evaporative demand and of carbon dioxide concentration. An on-field trial experiments were conducted in four randomized block treatments each having three replicates with varied water stress levels. The fields were planted with maize crops Duma 43 cultivar with different irrigation schedules ranging from 5, 7, 10 and 12 days irrigation intervals. The climatic parameters, soil and crop characteristics were used as input to the crop model and the results were used to assess the model performance. The AquaCrop model was calibrated and validated based on data obtained from irrigation schedules for the trial experiments and for the simulation period between 5th December, 2017 to 9th March, 2018. The model prediction indicated reasonable results: canopy cover range (R2 = 0.81 to 0.99), biomass production range (R2 = 0.89 to 0.98), and grain yields range (R2 = 0.82 to 0.96), however the model tracked the influence of soil, climate, crop parameters and seasonal evapotranspiration on crop growth. In 5 days irrigation interval the maize yield produced was 6.18 ton/ha when gross irrigation water depth of 1, 631mm (16, 310m3/ha) was applied. The 7 days irrigation interval produced 5.26 ton/ha under 1, 170mm (11, 700m3/ha), 10 days interval yielded 4.09 ton/ha with 792mm (7, 920m3/ha) and the 12 days irrigation interval produced 3.02 ton/ha under 672mm (6, 720m3/ha) respectively in the growing season. Optimization shown yield felt within 5 % of yield target for most of simulated treatments. The weekly (7 days) irrigation interval had the maximum maize yield with corresponding financial benefit achieved under limited water use. This was recommended irrigation schedule fit for effective arid to semi-arid regions water application for short season maize crop variety.
Keywords: Optimization, simulation, water scarcity, semi-arid environment