Impact of Irrigation Levels on the Growth, Yield, and Seasonal Evapotranspiration of Hard Red Winter Wheat.

The Southern High Plains (SHP) is a main winter wheat growing region of the USA. In this region, the Ogallala aquifer is the main source of irrigation; and it is depleting at an alarming rate. One way to slow down this depletion will be to decrease amount of irrigation in field crops without a substantial yield loss. Twenty hard red winter wheat genotypes, comprising of ten Texas lines and ten other varieties from neighboring states were grown at North Plains Research Field, Etter, Texas (36° 00’ N. latitude, 101° 59’ W. longitude, 3,618 elevations) in 2013. The irrigation treatment consisted of four levels, viz. 50, 65, 75, and 100% ET (control), and was provided with a center pivot system. The objectives were to determine optimum irrigation level for wheat without yield penalty, and to identify high yielding genotypes under deficit irrigation. There were significant effects of irrigation and genotype on all recorded traits; however, the effect of irrigation × genotype interaction was not significant except for the grain yield. There was no difference between the control and 75% ET levels for spike number and grain yield, when averaged across the genotypes; which decreased substantially at 65 and 50% ET levels. There was significant decrease in above ground biomass and the seasonal evapotranspiration at 75, 65, and 50% ET levels, when compared to the control. There was a significant effect of genotype on grain yield at every ET levels except 50% ET. In summary, this study showed that irrigation level of 75% is enough to produce as much spike number and grain yield as at 100% ET in SHP; which can save a substantial amount of irrigation water. The study also suggests that the irrigation level of 65% and below is not beneficial for producer in terms of growth and grain yield.