Low rainfall rarely limits wheat yields in southern New South Wales

Abstract

Alternative models were compared for predicting the yield of wheat (Triticum aestivum) from water-use and water-use efficiency. A locally derived empirical model most closely predicted experimental yields at Wagga Wagga and was used to compute water-limited potential yields for the district surrounding Wagga Wagga for the period 1960-84. District yields were close to the predicted potential in dry years, but reached a plateau of about 2.0 t/ha regardless of rainfall and the water-limited potential yield. The yields were less than 50% of potential when water-use exceeded 300 mm, which occurred in 19 years between 1960 and 1984. Some individual farmer-yields approached the potential. These results are similar to others from South Australia. Together, they suggest that low rainfall does not directly limit yield in many years over much of the wheat belt of southern and south-eastern Australia. We suggest therefore that an analysis of the reasons for low yield on farms could lead to substantial increases in yield for many farmers.