PLANTING DATE AND NITROGEN RATE EFFECTS ON SPRING MALTING BARLEY

Planting date (D) and N fertilizer have been shown to significantly increase spring malting barley (Hordeum vulgare L.) grain yield and protein when grown under dryland production systems where water is limiting. This study was conducted to determine D and N rate effects on grain yield, grain protein, kernel plumpness and yield components of spring malting barley grown under a production system that minimized crop water stress. Between 1984 and 1988, 'Klages' barley was planted at 2-wk intervals between 15 April and 19 May (expressed as days from 1 January) at Powell, WY on a Garland clay loam (fine, mixed, mesic, Typic Haplargid). Ammonium nitrate was applied at rates of 0, 67, 134, and 202 kg N ha-1. Early planting increased kernel weight 14% and kernel density 16% compared to late planting; spike density was not affected. Increasing N from 0 to 202 kg N ha-1 increased spike density 39% and kernel density 63%; kernel weight was not affected. Grain yield decreased from 4.7 to 4.0 Mg ha-1 with later planting date and increased from 3.4 to 4.9 Mg ha-1 as N rate increased from 0 to 202 kg N ha-1 [Grain yield (Mg ha-1) = 6.92 - 0.027(D) + 0.007(N); R2 = 0.89**, significant at P = 0.01]. Grain protein was unaffected by D and increased from 102 to 121 g kg-1 as N rate increased from 0 to 202 kg N ha-1 [Grain protein (g kg-1) = 127 - 0.194(D) + 0.095(N);R2 = 0.96**]. Kernel plumpness decreased from 97 to 95% with delayed D and was unaffected by N rate [Kernel plumpness (%) = 106 - 0.076(D) - 0.005(N); R2 = 0.80**]. Spring barley grain yield and kernel plumpness response to D and N rate for furrow irrigated cropping was similar to responses for dryland cropping. However, contrary to dryland results, grain protein was not affected by D when grown with minimum water stress.