Root: shoot ratio and water use efficiency differ in cool season cereals grown in pure and mixed stands under low and high water levels

This study examined the effect of low and high water levels on the root: shoot ratio (R:S) and water use efficiency (WUE) response of four cool season cereals [wheat ( Triticum aestivum , cv. TAM III), barley ( Hordeum vulgare , cv. P919), rye ( Secale cereale , cv. Elbon), and oat ( Avena sativa , cv. Walker)]. The pot experiment was conducted in the green house of Dryland Agriculture Institute, West Texas A&M University Canyon, Texas, USA during winter 2009-10. Hypothesis that crop stands and water level have no significant effect on R:S and WUE of field crops was tested in the trial. Significant variations in the R:S and WUE were observed for crops combinations and water levels. The increase in plants competitions in the mixed stands not only reduced roots and shoot biomass but also declined the R:S and WUE. The increase in R:S under low water was observed for all four crop species due to the increase in the root biomass and the corresponding decrease in the shoot biomass.