Impacts of use of observed and exponential functions of root distribution in soil on water utilization and yield of wheat, simulated with a crop model

Abstract

The suitability of two exponential distribution functions for the description of winter wheat root length distribution in a soil profile was examined. The impact of use of both the observed and fitted distribution functions as input parameters for simulation of wheat growth with the Crop Environment Resource Synthesis-Wheat crop model was determined. The fit between the observed and root distribution predicted with exponential functions was significant in all cases (R2 > 0.79, p < 0.01); in 8 of the 12 cases the fit was tight (R2 > 0.9). The simulation of the wheat crop growth was performed with 20 years’ daily meteorological data for clay-loam and loamy-sand soils. The impacts of using the observed or fitted exponential root distributions on growth and root distribution simulated with the crop model was negligible in those cases with a fit over about R2 > 0.9. In two cases with the worst fit (R2 = 0.79 and 0.82), the available water was reduced especially in sandy-loam soil, on average of years by 15 mm. On average, wheat yields decreased by 304 and 60 kg ha−1 for sandy-loam and clay-loam soils when the fitted exponential distributions were used compared with the observed ones.