Assessing planting date effects on seasonal water use of full- and short-season maize using SWAT in the southern Ogallala Aquifer region

Authors: Marek, Gary; CHEN, YONG - Texas A&M Agrilife; MAREK, THOMAS - Texas A&M Agrilife; HEFLIN, KEVIN - Texas A&M Agrilife; O`Shaughnessy, Susan; Gowda, Prasanna; Brauer, David

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2019
Publication Date: 10/30/2019
Citation: Marek, G.W., Chen, Y., Marek, T.H., Heflin, K.R., Oshaughnessy, S.A., Gowda, P.H., Brauer, D.K. 2019. Assessing planting date effects on seasonal water use of full- and short-season maize using SWAT in the southern Ogallala Aquifer region. Irrigation Science. 38:77-87. https://doi.org/10.1007/s00271-019-00653-3.
DOI: https://doi.org/10.1007/s00271-019-00653-3

Interpretive Summary: Declining water levels in the Southern Ogallala Aquifer region have led to interest in alternative management strategies to reduce groundwater withdrawals while maintaining profitable crop yields. The delayed planting of corn in the Texas High Plains is believed to reduce irrigation requirements by taking advantage of increased precipitation and reduced evapotranspiration demand. However, limited field data exist for corn planting dates in the region. Researchers from USDA-ARS at Bushland and Texas AgriLife Research used a calibrated SWAT model with long-term historical climate data to simulate corn irrigation and yields for both long and short season corn varieties. Simulation results suggested that delayed planting of corn resulted in decreased irrigation requirements with relatively small decreases in yield. Additional simulations showed that less frequent irrigations of greater application depth resulted in further water savings. These simulations suggest that the delayed planting of corn combined with effective irrigation management have the potential to reduce groundwater withdrawals from the Ogallala Aquifer.

Technical Abstract: A calibrated Soil and Water Assessment Tool (SWAT) model equipped with an alternative management allowed depletion (MAD) auto-irrigation algorithm was used to evaluate the effects of planting date on hybrid corn (Zea mays L.) yield and seasonal water use in the Texas High plains. Measured data from research fields at the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX and the Texas A&M AgriLife North Plains Research Field near Etter (NPRF), TX were used for model calibration. A composite, long-term (1925-2012) historical weather dataset was used to simulate continuous corn production using five planting dates (15-April, 1-May, 15-May, 1-June, and 15-June) for both long and short season corn hybrids. Results suggested that delayed planting resulted in a consistent reduction of seasonal water use for both long and short season varieties. Specifically, reductions in seasonal irrigation between the 15-April and 15-June were 28% and 31% for long and short season hybrids respectively, using an application depth of 25.4 mm (1 in). Corresponding reductions in yield were considerably less at 8.9 and 8.8% for long and short season hybrids. Reduced irrigation amounts were attributed primarily to decreased temperature stress and lower potential evapotranspiration of cooler, later growing season periods. However, simulation of long season corn for the 15-June planting resulted in increased late season cold temperature stress due to low temperatures. Further analysis of 19.1 mm (0.75 in) and 31.8 mm (1.25 in) irrigation application depths revealed the latter resulted in an average of 4.4 and 4.7% reductions in seasonal irrigation for long and short season hybrids, respectively. Reduced evaporative losses and greater infiltration associated with the larger application depths were attributed to the reductions in seasonal irrigation. Simulated corn yield and seasonal water use were in agreement with preliminary planting date field research data from the NPRF. Results from this assessment study suggest the delayed planting of corn may result in decreased irrigation requirements while maintaining profitable yields, potentially reducing withdrawals from the Ogallala Aquifer in the Texas High Plains region. Producers should be aware that some delayed planting dates may limit or preclude coverage by crop insurers.