The differential response of barley genotypes to nitrogen application in a Mediterranean-type climate

Abstract

The response of 12 barley cultivars to nine levels of nitrogen was studied in the field at Adelaide, S.A. The cultivars were selected from a world collection according to origin, number of spikelet rows and maturity, and their response was measured in terms of yield components, harvest index and straw and grain yield.

The optimum nitrogen level for grain production differed greatly between cultivars, some giving a maximum yield at 0 kg N/ha, others showing a typical parabolic response, and others giving increasing yields up to 275 kg N/ha. Although grain yields by cultivars at their optimal level differed the highest-yielding cultivars with optima at 0,70 and 275 kg N/ha had similar yields, which indicated that it would be more profitable to grow different cultivars in areas naturally low or high in soil nitrogen than to apply additional nitrogen to cultivars adapted to higher fertility levels. Some cultivars, previously considered as intrinsically lower-yielding, may normally receive suboptimal fertilization.

Variation in yields of cultivars with nitrogen reflected variation in ear numbers. The grain weight per ear remained relatively constant in 11 cultivars, as changes in weight per grain compensated for changes in number of grains per ear. In contrast, a single cultivar believed to be adapted to fertile prairie conditions was extremely susceptible to nitrogen deficiency, showing a large reduction in the number and aggregate weight of grains per ear.

The reduction in ear numbers at high nitrogen levels in some cultivars appeared to be related to temporary crop lodging in the juvenile stage prior to stem elongation. Late cultivars with many long, narrow leaves per tiller and many tillers were most prone to this pseudostem lodging.