Simulation of maize grain yield variability within a surface-irrigated field

Spatial variability of crop yield within a surface-irrigated field is relat ed to spatial variability of available water due to nonuniform irrigation a nd soil characteristics, among other factors (e.g., soil fertility). The in filtrated depth at each location within the field can be estimated by measu rements of opportunity time and infiltration rate or simulated with irrigat ion models, We investigated the use of the crop growth model EPICphase to s imulate the spatial variability of maize (Zea mays L.) grain yield within a level basin using estimated or simulated (with the irrigation model B2D) i nfiltrated depth. The relevance of the spatial variability of infiltration rate, opportunity time, and soil surface elevation in the simulation of gra in yield spatial variability was also investigated. The measured maize grai n yields at 73 locations within the level basin, ranging from 3.16 to 11.54 t ha(-1) (SD = 1.79 t ha(-1)), were used for comparison. Estimated infiltr ated depth considering uniform infiltration rate resulted in poor simulatio n of the spatial variability of grain yield [SD = 0.59 t ha(-1), root mean square error (RMSE) = 1.98 t ha(-1)]. Simulated infiltrated depth with the irrigation model considering uniform infiltration rate and soil surface ele vation resulted in grain yield simulations with lower variability than meas ured (SD = 0.64 t ha(-1), RMSE = 1.58 t ha(-1)). Introducing both sources o f spatial variability in the irrigation model resulted in the best simulati on of grain yield spatial variability (SD = 1.68 t ha(-1), RMSE = 1.16 t ha (-1); regression of calculated vs. measured yields: slope = 0.74, r(2) = 0. 56).