Simulating Semiarid Dryland Cropping Systems Using the Precision Agricultural Landscape Modeling System.

The Precision Agricultural Landscape Modeling System (PALMS) is a terrain and weather driven, distributed parameter hydrological-biophysical model primarily used in the Midwestern United States. Recently, research was started to evaluate the effectiveness of PALMS on dryland cropping systems in the semiarid Southern High Plains (SHP) of Texas. The accuracy of PALMS in semiarid climates needs to be assessed due to the contrasting nature of climate and soil type in the Midwest and SHP. Two characteristic soils in the SHP are the Amarillo series (fine-loamy, mixed, superactive, thermic aridic paleustalfs) and the Acuff series (fine-loamy, mixed, superactive, thermic aridic paleustalls). The hydraulic properties of these soil series are different than those previously used and tested in PALMS, and thus calculated values of the soil water balance need to be verified for the region of interest. A further objective has been included to determine if PALMS can simulate the effect of row orientation on the surface hydrology and rainfall capture in dryland agricultural fields. Two dryland locations under cotton and grain sorghum production in Dawson County, Texas were selected to evaluate PALMS and to study the effects of circular planting patterns on the surface hydrology and rainfall capture in semiarid dryland cropping systems. Soil water and plant growth monitoring were conducted at the selected locations during the growing seasons between 2007 and 2009 to compare the effects of circular planting to conventional linear planting patterns on the water balance of semiarid cropping systems. Results from field monitoring were compared to PALMS simulations to validate the model as well as to determine if the detail of input data was suitable. Initial results indicate that inclusion of measured soil hydraulic properties may be useful to increase the reliability of PALMS simulations in semiarid regions. Further results show that circular planting is effective for increasing rainfall capture and crop yield in semiarid dryland cropping systems.