|NELSON, JOHN - Kansas State University|
|BOOKER, JON - Texas Tech University|
|ZARTMAN, RICHARD - Texas Tech University|
Submitted to: Open Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2013
Publication Date: 8/1/2013
Citation: Nelson, J.R., Lascano, R.J., Booker, J.D., Zartman, R.E., Goebel, T.S. 2013. Evaluation of the precision agricultural landscape modeling system (PALMS) in the semiarid Texas Southern High Plains. Open Journal of Soil Science. 3:169-181.
Technical Abstract: Accurate models to simulate the soil water balance in semiarid cropping systems are needed to evaluate management practices for soil and water conservation in both irrigated and dryland production systems. The objective of this study was to evaluate the application of the Precision Agricultural Landscape Modeling System (PALMS) model to simulate soil water content throughout the growing season for several years and for three major soil series of the semiarid Texas Southern High Plains. Accuracy of the model was evaluated by comparing measured and calculated values of soil water content and using root mean squared difference, squared bias, squared difference between standard deviations, and lack of correlation weighted by the standard deviation. Different versions of the model were obtained by modifying soil hydraulic properties, including saturated hydraulic conductivity and residual and saturated soil volumetric water content, which were calculated using Rosetta pedotransfer functions. These modifications were combined with updated routines of the soil water solver in PALMS to account for rapid infiltration into dry soils that often occur on the Southern High Plains. Field studies were conducted across a wide range of soil and water conditions. Soil water content was measured by neutron attenuation and gravimetrically throughout the growing seasons at each location to compare absolute values and the spatial distribution of soil water with PALMS calculated values. Use of Rosetta calculated soil hydraulic properties improved PALMS soil water calculation from 1% - 13% of measured soil volumetric water content depending on soil type. Large-scale models such as PALMS have the potential to more realistically represent management effects on soil water availability in agricultural fields. Improvements in PALMS soil water calculations indicated that the model may be useful to assess long-term implications of management practices designed to conserve irrigation water and maximize the profitability of dryland and irrigated cropping systems on the Southern High Plains.