Simulation of efficient irrigation management strategies for grain sorghum production over different climate variability classes

Authors: KOTHARI, K - Texas A&M University; ALE, S - Texas A&M University; BORDOVSKY, J - Texas A&M University; Thorp, Kelly; PORTER, D - Texas A&M University; MUNSTER, C - Texas A&M University

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2018
Publication Date: 1/4/2019
Citation: Kothari, K., Ale, S., Bordovsky, J.P., Thorp, K.R., Porter, D.O., Munster, C.L. 2019. Simulation of efficient irrigation management strategies for grain sorghum production over different climate variability classes. Agricultural and Forest Meteorology. 170:49-62. https://doi.org/10.1016/j.agsy.2018.12.011.
DOI: https://doi.org/10.1016/j.agsy.2018.12.011

Interpretive Summary: Crop simulation models are increasingly being used as research tools to address a variety of agricultural issues, including assessments of irrigation management strategies for sorghum in semi-arid regions of the western U.S. The objective of the present study was to evaluate crop simulation models for sorghum and cotton using nine years of data collected at a research site near Halfway, Texas. The evaluated sorghum model was then used to identify optimal levels of soil moisture at planting and irrigation management strategies that optimized sorghum yield and water use. Results showed that initial water content of 75%, triggering irrigation at 50% soil water, and irrigating to 85% soil water was sufficient for sorghum production in cold, wet years. However, in warm, dry years, triggering irrigation at 60% soil water and irrigating to 100% soil water was necessary to prevent sorghum yield loss. The study will be most useful for scientists, researchers, and producers who require irrigation management recommendations for sorghum production systems.

Technical Abstract: The Texas High Plains (THP) is a productive agricultural region, and it relies heavily on the exhaustible Ogallala Aquifer for irrigation water for crop production. Efficient use of irrigation water is critical for the sustainability of agriculture in the THP. Grain sorghum is one of the major crops grown in the region, and it is known for its drought tolerance and lower water requirement compared to other cereal crops such as corn. In this study, the CERES-Sorghum and CROPGRO-Cotton modules of the Decision Support System for Agrotechnology Transfer (DSSAT) were evaluated using data from cotton-sorghum rotation experiments at Halfway, Texas over a period of nine years (2006-2014). The evaluated CERES-Sorghum module was then used to identify the optimum (i) initial soil moisture at planting (ISM); (ii) soil moisture threshold to start irrigation (ITH); and iii) deficit/excess (DFI) irrigation strategy for grain sorghum production based on simulated sorghum yield, irrigation water use efficiency (IWUE), and grain water use efficiency (WUE). In addition, the effect of weather conditions on simulated strategies was elucidated by dividing the long-term (1977-2016) weather data into cold, warm, wet, dry, and normal climate variability classes based on the 33rd and 66th percentiles of growing season temperature and precipitation. The DSSAT model adequately simulated grain sorghum and seed cotton yields during calibration (average Percent Error (PE) of 1.3% and 3.4%, respectively) and evaluation (average PE of -2.2% (sorghum) and -10.5% (cotton)). The results from long-term simulations indicated that weather conditions played a key role in selecting appropriate irrigation management strategies. Under normal/cold/wet weather, ISM of 75% of plant Available Water Content (AWC), ITH of 50% AWC, and DFI 85% were found to be adequate for irrigated grain sorghum production. However, in warm/dry weather, ISM of 75%, ITH 60%, and DFI at 100% reduced sorghum yield loss.