EFFECT OF NITROGEN-FERTILIZER ON THE YIELD AND QUALITY OF 6 CULTIVARS OF AUTUMN-SOWN WHEAT

A field experiment was conducted to evaluate the effect of various rates and timings of nitrogen (N) fertiliser application on yield, grain quality, quantities of various classes of proteins, and milling and baking characteristics of New Zealand wheat cultivars. Six cultivars of autumn-sown wheat-'Batten', 'Kotare', 'Oroua', 'Rongotea', 'Ruapuna', and 'Tui'-were grown under five N fertiliser treatments: no N; 50 kg N/ha applied at late tillering; 50 kg N/ha applied at both late tillering and booting; 100 kg N/ha applied at late tillering; and 100 kg N/ha applied at late tillering and 50 kg N/ha applied at booting. The site was severely N depleted and ear numbers were low. However, weight per grain was high and relatively unaffected by N fertiliser. Grain yield, grain protein, and Mechanical Dough Development (MDD) Bake Score increased with increasing fertiliser N, irrespective of time of application, but, between cultivars, yield was inversely related to both grain protein and bake score. No one cultivar produced a flour with good values of all the quality characteristics. Nitrogen fertiliser improved flour and bread making quality, especially when applied at booting. There were highly significant correlations between high and low molecular weight glutenins, work input loaf volume, and bake score. Loaf texture was highly significantly correlated with both gliadin and kernel weight.