Constraints on water use efficiency of drought tolerant maize grown in a semi-arid environment

- The high stress environment significantly constrained the yield and water use efficiency of the more stress tolerant hybrid as well as those of the less tolerant hybrid.
- Crops grown in the sandy loam and fine sand had larger WUE compared with those grown in the clay loam and silt loam, especially under limited irrigation.
- One hybrid out yielded the other hybrid while using the same or significantly smaller amounts of water.

Identifying the constraints on crop water use efficiency (WUE) will help develop strategies to mitigate these limitations, potentially guiding agronomic and irrigation management strategies as well as providing needed directions in breeding. Boundary functions identify the upper limits of yield per unit of crop water use, and are useful for identifying constraints on WUE. The objectives of this research were to (1) develop a boundary function for maize using data (n = 260) from research projects conducted at Bushland, TX, and (2) compare the yields of two recently developed, drought tolerant maize (Zea mays L.) hybrids with the boundary function and examine possible abiotic and biotic constraints on maximizing water use efficiency. A commercially available hybrid and an experimental hybrid were grown in 2012 (high environmental stress environment) and 2013 (moderate stress environment) in 48 weighing lysimeters containing soil monoliths of either clay loam, silt loam, sandy loam, or fine sand in a rain shelter facility. Plant density was 8 plants m−2; irrigation treatments were 50% and 80% replacement of predicted crop evapotranspiration. The high stress environment of large vapor deficits and high temperatures during early reproductive growth stages in 2012 compared with 2013 significantly constrained the yield potential of both hybrids. It also showed the difference in stress tolerance of the hybrids with significant differences in WUE, yield and yield components between hybrids. Soil textural class was a significant constraint on WUE and harvest index (HI), with larger WUE and HI from crops in the fine sand and sandy loam compared with those of the crops in the clay loam and silt loam. Continued increases in the tolerance of maize to abiotic and biotic stresses will be necessary to maintain maize production in the southern High Plains region as irrigation water resources decline.