Soil water extraction and use by winter wheat cultivars under limited irrigation in a semi-arid environment

Authors: THAPA, SUSHIL - Texas Agrilife Research; XUE, QINGWU - Texas Agrilife Research; JESSUP, KIRK - Texas Agrilife Research; RUDD, JACKIE - Texas Agrilife Research; LIU, SHUYU - Texas Agrilife Research; DEVKOTA, RAVINDRA - Texas Agrilife Research; BAKER, JASON - Texas Agrilife Research

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2019
Publication Date: 11/6/2019
Citation: Thapa, S., Xue, Q., Jessup, K., Rudd, J.C., Liu, S., Devkota, R.N., Baker, J.A. 2019. Soil water extraction and use by winter wheat cultivars under limited irrigation in a semi-arid environment. Journal of Arid Environments. 174. Article 104046. https://doi.org/10.1016/j.jaridenv.2019.104046.
DOI: https://doi.org/10.1016/j.jaridenv.2019.104046

Interpretive Summary: Water supply and distribution over the growing season are the main limiting factors to winter wheat yield in the semi-arid U.S. southern Great Plains. To manage crop water demand, limited irrigation (also called deficit irrigation) is commonly practiced in the region. Working in a project funded by the USDA ARS Ogallala Aquifer Program, scientists with Texas AgriLife Research evaluated yield of winter wheat varieties as influenced by the depth and amount of net soil water extraction (SWE) under limited irrigation. Only 2.5 inches of seasonal precipitation occurred in the 2011 (historic drought) season and the net SWE was limited to the upper 4 feet of soil. In 2016, 12 inches of seasonal precipitation occurred and the net SWE extended to 6 feet in the soil. Grain yield was largely influenced by the amount of net SWE during the growing season. Hence, ensuring early plant growth to promote root development for extracting soil water from the deeper profile later in the season should be a key strategy to take full advantage of limited irrigation.

Technical Abstract: Water supply and distribution are the main limiting factors to wheat (Triticum aestivum) yield in a semi-arid region of the U.S. southern Great Plains. To manage crop water demand, limited irrigation (also called deficit irrigation) is commonly practiced in the region. A 4-yr study was conducted to evaluate yield in winter wheat cultivars as influenced by the depth and amount of net soil water extraction (SWE) under limited irrigation. For timing the irrigation application, we considered critical growth stages (jointing, tillering, and anthesis) as well as soil water depletion at the crop root zone below 50%. Volumetric soil water content was measured in 0.2'm increments to the depth of 2.4'm'at planting, jointing, anthesis, and physiological maturity. Since the irrigation capacity was limited, seasonal precipitation was still an important factor for determining SWE. The 2011 season was one of the historic drought seasons with only 60'mm of seasonal precipitation and the net SWE in that season was limited to the upper 1.2'm profile. In contrast, the 2016 season was more favorable for crop growth with 315'mm of seasonal precipitation and the net SWE in that season reached to 2.0'm deep. Grain yield was largely influenced by the amount of net SWE during the growing season. For the wheat with grain yield of 4807'kg'ha-1, net SWE was 165'mm (2016). However, wheat with grain yield of 2933'kg'ha-1 only extracted 70'mm stored soil water (2011). The 2012 and 2017 seasons remained intermediate in terms of seasonal precipitation, SWE, and yield. Although the 2011 and 2016 seasons had similar stored soil moisture at planting, more early-season as well as total precipitation in 2016 appears to have enabled plant growth to access the deeper water. In contrast, a greater amount of stored soil water was left unused at the end of the 2011 season due to drought and poor plant growth. Hence, in addition to adding water at critical growth stages, ensuring early plant growth to promote root development for extracting soil water from the deeper profile later in the season should be a key strategy to take full advantage of limited irrigation.