Evaluating the Soil Moisture and Plant Growth of Guayule Using Remote Sensing and the WINDS Model With Subsurface Drip and Flood Irrigation

Abstract

The purpose of this research is to simulate the soil water content of a two-year guayule crop grown in sandy loam soil with both furrow and subsurface drip irrigation (SDI) treatments using the WINDS model. The simulated soil water content was compared to actual soil moisture measurements taken by a neutron moisture meter (NMM) in order to calibrate the model. The irrigation experiment implemented six irrigation treatments where five of them were subsurface drip irrigation, (SDI) with application rates of 50, 75, 100, 125, and 150% of estimated crop evapotranspiration [ET] (D50, D75, D100, D125, and D150). The D100 was the control treatment. There was also a 100% flood irrigation treatment (F100). The experiment consisted of a split-plot design with field location as the main plot and the treatments as the split-plots. The treatments were randomly assigned in each block area. One objective of this research is to model the wetting patterns and soil water content of guayule with SDI. This is done through a configuration process that adjusts the fraction of total wetted width of soil layers in the soil profile. Establishing a reliable configuration process was critical towards creating WINDS soil moisture simulations for guayule. In addition to the fraction wetted procedure, other configuration-based activities consist of setting root growth curves, ET fraction changes for layers in the root zone and creating plant growth and crop coefficient curves that rely upon remote sensing measurements. In addition, soil property calibration methods were established based on observed moisture contents in the field. The primary soil parameters in this research were field capacity (FC) and permanent wilting points (PWP) for the soil layers.