Comparison of lysimeter-derived crop coefficients for legacy and modern drought-tolerant maize hybrids in the Texas High Plains

Authors: Marek, Gary; MAREK, THOMAS - Texas A&M Agrilife; Evett, Steven - Steve; BELL, JOURDAN - Texas A&M Agrilife; Colaizzi, Paul; Brauer, David; HOWELL, TERRY - Retired ARS Employee

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2020
Publication Date: 12/1/2020
Publication URL: https://handle.nal.usda.gov/10113/7224984
Citation: Marek, G.W., Marek, T.H., Evett, S.R., Bell, J.M., Colaizzi, P.D., Brauer, D.K., Howell, T.A. 2020. Comparison of lysimeter-derived crop coefficients for legacy and modern drought-tolerant maize hybrids in the Texas High Plains. Transactions of the ASABE. 63(5):1243-1257. https://doi.org/10.13031/trans.13924.
DOI: https://doi.org/10.13031/trans.13924

Interpretive Summary: Producers in the semiarid Texas High Plains rely on groundwater from the declining Ogallala Aquifer for irrigation to supplement inadequate precipitation for corn production. The use of daily reference evapotranspiration and crop coefficient (Kc) values are commonly used in irrigation scheduling to maximize crop water productivity. However, questions about the applicability of Kcs derived from legacy corn hybrids to modern drought tolerant (DT) hybrids have been raised. Researchers from USDA-ARS Bushland and Texas A&M University compared lysimeter-derived Kcs from legacy and modern DT corn hybrids grown in large weighing lysimeter fields at the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX. Although maximum daily Kc values were similar for all hybrids, the average season length of the DT hybrid was approximately 25 days shorter than that of the legacy hybrids, characterized by a shortened initial growth period followed by increased slope during the development period. Comparisons of published and fitted Kc functions illustrated the effect of environment on crop water use and reinforced the importance of climate-specific Kcs. Farmers and crop consultants that use evapotranspiration data to schedule irrigation need to be aware of changes in growth characteristics of modern DT corn hybrids so that they can better match applications with crop needs and reduce pumping costs and water use.

Technical Abstract: Corn (Zea mays L.) is a major irrigated crop grown in the Southern High Plains including the Texas Panhandle. Irrigation from the Ogallala Aquifer is required to sustain profitable corn production in the region by supplementing inadequate and erratic rainfall. Effective irrigation scheduling works to extend limited groundwater resources by avoiding water losses associated with runoff and/or percolation below the rooting zone. The use of crop coefficients (Kcs) and reference evapotranspiration (ETo) to estimate daily crop water use (ETc) remains an effective scheduling tool that can complement other irrigation scheduling approaches. Both Food and Agriculture Organization (FAO-56) piecewise and curvilinear Kcs for corn are found in the literature. However, advances in cultivar genetics have led to questions about the applicability of Kcs developed using legacy corn varieties to modern drought tolerant (DT) hybrids. Lysimeter-derived Kcs from legacy corn hybrids grown in large weighing lysimeter fields at the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX were compared with those derived from a modern DT corn hybrid recently grown in the same fields. Results indicated that although maximum daily Kc values were similar for all hybrids, average season length was approximately 25 days shorter for the DT hybrid, characterized by a shortened initial growth period followed by increased slope during the development period. Presented data suggest that the modern DT hybrids may be more effective at assimilating yield from ETc during periods of heat stress in semi-arid environments, resulting in a shortened season relative to legacy full-season corn hybrids. Both FAO-56 and curvilinear Kcs for the legacy and the DT grown in the Texas High Plains are presented and discussed.