Water use by wheat on the Canterbury Plains

Abstract

This study analysed the 'on-farm' water use and water use efficiency of 36 autumn and winter sown wheat crops in Canterbury. These crops were divided into 7 groups based on their geographical location. Simple non-parametric tests were used to determine whether there were differences in either water use or water use efficiency between these locations. The crops at Kirwee were found to have significantly higher water uses than those at Lincoln, Irwell and Timaru. Mean water use at Kirwee for the period 1/9/90 to 1/1/91 was 403 mm (sd=23mm). This was compared with 330mm (sd=19mm), 289mm (sd=41mm), and 321mm (sd=19mm) for Lincoln, Irwell and Timaru crops, for the same period, respectively.

An apparent significant difference in water use efficiency between crops at some of the locations was later disregarded because of the effects of possible capillary rise of water at one, and of the late sowing dates at another location. It was the conclusion of this study that the differences found in water use between the crops at Kirwee and at Lincoln, Irwell and Timaru were probably caused by differences in the saturation deficit of the air at the locations. High air saturation deficits occurred during periods of north-westerly winds when both ETp and crop water use were found to be highest. The north-westerly wind was shown to occur more frequently and with greater force at Kirwee.