Soil moisture is the component in the hydrologic water balance which controls land water interaction through water and energy balances. Soil moisture content in the root zone influences evapotranspiration (ET); evapotranspiration decreases as soil water content decreases. If the available soil moisture does not meet the water requirements of the crop, the ET decreases and the crop undergoes moisture stress. Plant available soil moisture is positively correlated with crop yield. However, soil moisture may differ greatly from region to region and among the differing soil textural classes. In general, coarse-textured sandy soils have lower water holding capacities than fine-textured clay-based soils. Also, topography affects the amount of available water to plant through horizontal and vertical water distribution. Basically, water applied to the field either by rainfall or irrigation accumulates in relatively lower areas of the field, increasing available soil moisture which results in relatively higher yields. Though uniform amounts of fertilizer are typically applied to the entire field, redistribution of the material could cause significant variations in yield. Interaction of weather factors with topography could cause difference in crop growth and yield. Climatic parameters like rainfall, air and soil temperature, solar radiation and humidity are other factors determining soil moisture and ultimately crop yield of the area.
The drought of 2012 reduced yields of many field crops (wheat, corn and soybean) in the central USA. On a local scale, high spatial variability in yields were observed as related to topography. My research will focus on the integrated influence of soil texture, topography, and climate in soil moisture and crop yields. Quantification of the effect of topography in soil moisture and crop yield will allow the development of improved management strategies at the field level. I will examine the influence of topography with a process-based crop simulation model that allows hypothetical experimentation of crop yield response to a variety of input factors including climate.