New Method for Modeling Daily Available Soil Moisture Through the Growing Season.

Drought stress is one of the key yield-limiting factors faced by corn crops planted in the Midwestern United States. Having the ability to understand the timing and persistence of drought stress events based on a model of available water content at the field level, and also having the ability to aggregate that information up to larger regional and state levels allows for an understanding of the yield shortfalls that may be seen in individual fields, counties, regions and states in any given year. 

Using a newly developed, highly granular soil moisture model that considers soil type, daily rainfall, daily temperature, crop and crop growth stage, we will be tracking the timing and persistence of drought stress for each day of the 2012 crop season (April 1 to September 30) for every 2.5 x 2.5 mile square of land in Iowa, Illinois and Indiana.  Soil moisture values will be calculated for each grid for each day of the season based on an assumption of corn as the crop in the field .  The soil moisture model used in this study will be built on rainfall data from the AHPS data set (which reports rainfall for every 2.5 x 2.5 mile square of land in the country), a new gridded temperature data set, and soil type information from a gridded version of the SSURGO dataset.

The drought stress model that we will run differs from existing drought models such as PDSI and SMI in that it provides results at a resolution approaching field level, it identifies each individual day of drought stress to allow for differentiation between days of drought stress that occur in isolation and days of drought stress that come in succession, and the evapotranspiration factor in the model is dependent on the assumption of corn as the planted crop. Results of this study will allow better understanding of the role drought played in limiting yields for the 2012 corn crop in specific geographic locations across Iowa, Illinois and Indiana.