An analysis of a nitrogen-induced depression of yield in irrigated 'Kopara' wheat

Abstract

Heavy applications of nitrogen fertiliser (200 kg/ha) applied in early spring to wheat (Triticum aestivum L. cv. 'Kopara') on a Wakanui silt loam, in which irrigation was used to maintain soil-water levels above -0.5 bar, depressed grain yield by 30%. Poor grain set was the main cause of the low yields, but mean grain weights were also reduced. Analysis of data indicated that grain set was probably restricted by the availability of carbohydrate during the critical pre-anthesis period of floret development.