Effect of sowing date and nitrogen on dry matter and nitrogen partitioning in malting barley

Variation in yield and quality of malting barley (Hordeum vulgare L. 'Triumph') are major problems for both producers and processors in the Manawatu, New Zealand. Climatic variation is partially responsible for this. However, crop management options may enable the variation to be reduced. The effects of sowing date and nitrogen (N) fertiliser on yield and quality of malting barley were evaluated over two seasons. In 1987/88, a grain yield of 7.0 t/ha was achieved with optimal management. Yields in 1988/89 were approximately half those in the previous season because of drier conditions during grain filling and a greater incidence of disease. N uptake was lower hi the second season, but this did not result in lower grain N content and, therefore, improved quality because dry matter (DM) yield was also lower. Grain N concentrations were significantly higher in the late sowings in both seasons. Differences in grain N concentrations were related to the timing of N accumulation in the plant. Over all sowings, the contribution of post-anthesis N uptake relative to total grain N was negatively related to grain N concentration (r=-0.78). This indicated that late N uptake may not always be detrimental to quality as the processes of carbon and N accumulation are closely linked during grain filling. The maintenance of green leaf area by fungal disease control or timely irrigation is considered important for maintaining high grain quality as these prolong the accumulation of DM during grain filling.