Yield and quality of malting barley (Hordeum vulgare L-'Valetta') in response to irrigation and nitrogen fertilisation

Interactions of soil water and nitrogen (N) fertiliser application on the quality of barley (Hordeum vulgare L. 'Valetta') for malting were studied in a rain shelter experiment at Lincoln, New Zealand. Treatments were arranged in a factorial design, consisting of five levels of soil water (fully irrigated, rain-fed, early drought, late drought, and full drought) and four levels of N fertiliser (nil, 1 x 50, 2 x 50, and 3 x 50 kg N/ha). N treatments were applied at emergence, appearance of the second node, and at flowering, respectively. Variables indicative of grain quality (N concentration, grain size, and screenings) and micro-malting characters (water uptake, malting loss, N index, wort-N, beta-glucan, fine extract, coarse extract, and fine-coarse difference) were evaluated for responses to the water and N treatments. Drought influenced the distribution pattern of kernel mass along the main stem and tiller spikes and also influenced the relative proportions of grain in the standard size categories. The level of N fertiliser had little effect on the kernel size properties. Screenings originated from both the proximal and distal ends of tiller spikes and from the proximal end of the main stem spike. The less severely water stressed treatments had fewer small kernels and, mean weight of kernels was greater over all kernel positions. Grain N concentration responded to N fertiliser application but was unresponsive to water treatment. The reverse was true for kernel size and the malting characters of water uptake, malting loss, extract levels, and fine/coarse difference. Drought increased the levels of wort P-glucan and lowered wort N and N index whereas N fertiliser caused an increase in wort P-glucan and wort N but lowered the N index. Interactions between water and N effects were only significant for the latter. Both the timing of drought and fertiliser treatment had strong effects on the biochemical and physical characteristics of grain.