Monday, November 13, 2006

Improving Irrigated Cropping Systems on the High Plains Using Crop Simulation Models.

Christopher Pachta, Kansas State Univ., 3709 Throckmorton Hall, Manhattan, KS 66506 and Scott Staggenborg, Kansas State University, 2004 Throckmorton Plant Sci. Ctr, Manhattan, KS 66506, United States of America.

Current irrigated cropping systems in the High Plains region are dominated by water intensive corn (Zea mays L.) production, which along with other factors has caused a decline in the Ogallala aquifer.  There is the potential to decrease the demand for water from the aquifer by the inclusion of drought tolerant crops such as grain sorghum (Sorghum bicolor L.) and cotton (Gossypium hirsutum L.) into the cropping systems of this region.  The objectives of this study are to calibrate the CERES-Maize, CERES-Sorghum, CROPGRO-Cotton models for the High Plains region and to study the simulated effects of the inclusion of grain sorghum and cotton into traditional corn cropping systems on overall water use.  Input files were created from research plots in Hugoton, Pratt, Hutchinson, Scandia, and Manhattan, Kansas to calibrate the models.  Information collected at the research sites for these data sets included: soil physical properties, dry matter, leaf area, initial and final soil water content, management, and weather.  Models in DSSAT were used to simulate the inclusion of grain sorghum and cotton into the cropping systems and evaluate the water use of these different cropping systems.  Preliminary validation results using data collected in 2005 in Hugoton and Pratt had CERES-Maize predicting yield within 13% of the actual yields over the two locations.  Simulated peak LAI was 40% of the measured value and peak specific leaf area (SLA) was 36%.  Kernel number, kernel weight, and ear number were simulated within 38, 12, and 2% of the corresponding measured values, respectively.  The CROPGRO-Cotton model simulated yield was 17% of the measured yield at the two locations. Peak LAI and SLA were 37 and 23%, respectively of the measured values.  Simulated boll number was 15% of the actual.  Calibration continues on the CERES-Maize and CROPGRO-Cotton models along with CERES-Sorghum.