The effects of soil moisture stress at different stages of development on the grain yield of two New Zealand wheat varieties

The importance of the wheat plant needs no emphasis. Among the cereals it is second to none in economic importance and in total yearly production. In New Zealand, of course, it is the most important of all arable crops; its production and the acreage of land devoted to its growing continue to increase (Copp, 1962-64; N.Z. Wheat Rev. 9:11-19). Although catastrophic droughts, such as those known in U.S.A., U.S.S.R. and India, are not known in the wheat growing areas of New Zealand, yields are quite often dependent on the availability of water. This is particularly true in the growing areas of the Canterbury Plain. It is very surprising that virtually no work has been done in New Zealand on the effect of drought on the yield of this important crop. Investigations seem to be concentrated on the disease aspects and on mineral requirements of the plant. The present investigation was, therefore, intended to give some indication of the drought susceptibility or resistance of New Zealand wheats. It was designed to compare the sensitivity (expressed in grain yield) of the different stages of development of the plant to soil-moisture stress. The stages of growth chosen for the imposition of the drought treatment are those currently thought to be critical in moisture availability. For the sake of simplicity only mother shoots were used in the study - all other tillers being removed soon after they appeared. Two New Zealand varieties, Arawa and Hilgendorf '61, were used - both of which are widely grown in the South Island. These two varieties were chosen because they differ in the make-up of their yield (Langer, 1965), and it seemed likely that this would be reflected in their reaction to drought imposed at different stages of development.