In this study we provide recommendations for optimal and minimal irrigation capacities for grain sorghum production in western Kansas using long-term crop water production functions and water use efficiency for different irrigation strategies. We used both field trials and computer simulations using the Decision Support System for Agrotechnology Transfer- Cropping System Model (DSSAT-CSM) to create curves of crop yield response to water also known as production functions.
We also compared two cultivars of grain sorghum, early and late maturity, three irrigation scheduling scenarios and four different irrigation capacities as well as rainfed and full irrigation. From these scenarios, we modeled yield outcomes then evaluated against long-term water use efficiency.
Our results indicated irrigating grain sorghum in Western Kansas from the panicle initiation to grain-fill was optimal for maximizing yield and crop water productivity. To achieve a yield target goal of 80 bu/ac, minimum irrigation capacity required is 0.07-0.1 in/day and to achieve a yield target goal of 96 bu/ac this increases to 0.14 in/day. Applications over 0.14 in/day had little impact on yield.
Higher irrigation capacities resulted in less significant increases in yield due to poor crop water utilization and higher losses to drainage. There is a need for further research on the economic aspects of irrigation, water use efficiency, and yield as these are necessary for insights to farm-level profit and risk.
Publication: Araya, A., I. Kisekka, P.H. Gowda, and P.V.V. Prasad (2018). Grain sorghum production functions under different irrigation capacities. Agricultural Water Management.