|dc.description.abstract||Two field experiments were carried out on a medium, moderately fertile soil in Canterbury in the 1984-85 and 1985-86 growth seasons. The aim was to investigate and analyse the effect of sowing date, cultivar and disease on grain yield and yield components of barley with respect to growth and development. The first experiment included two barley cultivars; Triumph (2-row spring barley) and Sonja (2-row true winter barley) sown at four dates in May, June, July and September. Half the plots were treated by fungicides for disease control. Dry matter accumulation, yield components and grain yield were measured and maximum crop dry matter, weighted mean absolute crop growth rate, maximum absolute crop growth rate and the effective length of crop growth were calculated. Disease incidence and non green leaf area were assessed. The delay in sowing from autumn to spring reduced an average grain yield of Triumph from 7 to 5.3 t ha⁻¹ and Sonja from 6 to 2.5 t ha⁻¹. The yield advantage for autumn sowing was due to the higher number of ears per unit area (both cultivars), number of grains per ear (Sonja) and mean grain weight (Triumph). Triumph generally produced a higher yield than Sonja because of a greater number of ears per unit area and number of grains per ear. In the absence of disease, the mean efficiency of conversion of accumulated intercepted radiation to final total dry matter was 0.7 g MG⁻¹ Thus, the improvement in grain yield with autumn sowings in disease-free conditions was associated with a greater total dry matter production at maturity and related to a larger amount of total radiation intercepted by the crop. Diseases, mainly scald and leaf rust, reduced grain yield of Triumph by 13-60 % and Sonja by 22-63 %. These reductions were associated with the increase in percent non green leaf area. As a consequence, the efficiency of radiation conversion to final total dry matter appeared to be lower when diseases were present particularly at the spring sowing. Diseases also reduced weighted mean absolute crop growth rate, the maximum crop growth rate and an individual grain weight. Plant population of Sonja at the May and July sowings was reduced by the seed treatment chemical (Triadimenol plus fuberidazole) by 27 and 37%.
Illia, a 6-row true winter barley, was compared with Triumph in the following season. The crop was sown at six dates in early May, late May, July, September, October and November. Disease was controlled in all plots. Dry matter accumulation, the peak number of tillers, percent tiller survival, grain yield and yield components were measured. Delaying the sowing from autumn to spring reduced grain yield of Triumph from 5.5 to 4.6 t ha⁻¹ and Sonja from 7.6 to 3 t ha⁻¹. The higher yields for autumn sowings were associated with the higher final total dry matter accumulation and related to a longer duration of growth. Illia produced a higher yield than Triumph at the autumn sowings, but Triumph out yielded Illia when sown in spring. Illia failed to produce ears from October and November sowings presumably due to a lack of vernalization.
Drought avoidance and consequent higher yield is the main advantage for autumn sown barley compared with spring sowing providing that the available soil moisture is adequate during autumn and winter. This practice is likely to become widely adopted by cereal growers in New Zealand particularly if a high malting quality winter barley can be bred. The present studies show that Triumph has a moderately high yield potential when sown in autumn providing that disease is controlled. This is because autumn sowing increases the risk of disease problems. Despite a costly disease control programme, the grain of Triumph is acceptable for malting. This cultivar should be a reasonable choice for the farmer until a newly bred true winter cultivar with high quality together with disease resistance is available. Illia and Sonja, because they are only feed barleys, command a much lower price. However, Illia is more attractive than Sonja for the autumn sowings because of its higher yield potential and disease resistance.||en