Sustainability of Cropping Systems for Dryland Winter Wheat Production: A Simulation Approach.

Abstract:

Conventionally tilled dryland winter wheat followed by a 14-month period of fallow is the predominant cropping system for winter wheat production in the High Plains Ecoregion of Wyoming. Although practical, the system seems to be inefficient as soil water storage efficiency during fallow is frequently less than 25% as compared to conventional tillage. Alternative to this system can be no-till, which may increase yield while conserving soil water, the major limiting factor for dryland production. The objectives of this study were to determine long term effects of cropping system on yield, water content and water productivity of dryland winter wheat under conventional and no-till.  A field experiment with three replicates was conducted at the University of Wyoming Sustainable Agricultural Research and Extension Center (SAREC), near Lingle, WY, USA. The experimental data was used to calibrate the Cropping System Model (CSM)-CERES Wheat of the Decision Support System for Agrotechnology Transfer (DSSAT). The calibrated model was then used to simulate soil water under no-till and conventional cropping systems and to investigate the effect of the cropping systems for yield and water productivity of wheat using management practices, soil and 27 years of historical weather data representing the southeastern region of Wyoming.  The non-parametric Kolmogorov-Smirnov procedure was used to determine differences between cumulative distribution functions of simulated soil water content between no-till and conventional cropping systems. The model simulated the winter wheat yield with an RMSE of 952 kg ha^-1 under the conventional system and 994 kg ha^-1 under the no-till system. In the long-term, the no-till system resulted in higher yields compared to the conventional system. Water productivity of dryland winter wheat was not affected by the cropping systems. The no-till field resulted in same extractable water at maturity and higher soil water content compared to conventional field; therefore providing low risks of water stress for the next crop. These results also suggest that the no-till system may be an option for intensive crop rotation compared to the traditional CT wheat-fallow rotation. Further studies include alternative crops to fallow and their impact on soil moisture for the following wheat cycle.