Submitted to: Open Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2020
Publication Date: 7/17/2020
Citation: Lascano, R.J., Leiker, G.R., Goebel, T.S., Mauget, S.A., Gitz, D.C. 2020. Water balance of two major soil types of the Texas High Plains: Implications for dryland crop production. Open Journal of Soil Science. 10:274-297. https://doi.org/10.4236/ojss.2020.107015.
Interpretive Summary: Agriculture in the Texas High Plains (THP) is changing and we are growing more of our crops using less irrigation water as it was done in the early part of the 20th century. Why is this taking place? The answer to this question is related to the fact that the irrigation-water from the Ogallala aquifer is more expensive to pump because the depth to the water table continues to increase. The Ogallala is a large aquifer that extends across 8 states of the Great Plains and in Texas, the aquifer is what is called a closed system, meaning water can only be extracted and not be replenished. The effect of this characteristic is that in several counties of the THP, the Ogallala aquifer has reached a point where it is no longer sustainable to irrigate crops. This means that producers will depend on water from rain to grow their crops. To address this problem and to seek solutions, ARS scientists in Lubbock, Texas used a simulation model to study the impact of a dry (7 inches), an average (18 inches) and a wet (26 inches) year of rainfall for two major soil types of the THP, Pullman in the north and Amarillo in the south. The results showed that for an average and wet year the Pullman soils can store water from the rainfall. However, this was not the case for the Amarillo soils. The good news is that we have at our disposal management practices such as minimum tillage and ground cover residue that can be used to enhance the capture of rainfall and assure adequate soil water to successfully grow crops.
Technical Abstract: Crop production in the Texas High Plains is shifting from irrigated to dryland due to the increase of the depth to the water table from the Ogallala aquifer in regions where the saturated thickness of 9 m, the minimum to sustain irrigation, has been reached. Our objective was to use the mechanistic model ENWATBAL to evaluate the daily and annual water balance for three scenarios of rainfall in this region, a dry (189 mm), an average (449 mm) and a wet (669 mm) year. These three scenarios were applied to two major soil series of this region, Pullman and Amarillo. In all simulations, we used hourly input weather data for a location near Lubbock, Texas and used measured soil hydraulic properties to simulate the water balance for each soil series and the three rainfall scenarios. Results showed that in years with average and wet rain, storage of rainfall occurred in the Pullman but not in in the Amarillo soil series. However, storage could be enhanced by combining furrow dikes with minimum tillage along with crop covers that provide a surface residue. The implications of our results for dryland crop production in the semiarid climate of the THP suggest that for years with average and wetter rainfall soils in the Pullman series could store water that would be available for crop use. However, this was not the case for the Amarillo soil series and these soils represent a higher risk for crop production.