Fertilizer Effects on Yield, Grain Composition, and Foliar Disease of Doublecrop Soft Red Winter Wheat¹

Abstract

Abstract Improvements in cultivars and management technology have increased the yield potential of soft red winter wheat (SRWW) ( Triticum aestivum L.). Field experiments were conducted for 3 yr to define fertilizer requirements for doublecrop SRWW grown on Sharkey clay soil (Vertic Haplaquent). Nitrogen rates were 0, 34,56,78, and 101 kg ha −1 applied as both a single February topdress application (growth stage 5, Feeke's scale) and as a fall‐February split with 17 kg of the total N applied preplant. The effects of application of P (20 kg ha −1 ) and K (24 kg ha −1 ) were evaluated singly and in combination at a February applied N rate of 56 kg ha −1 and fall + February split N application rates of 17 + 39 and 17 + 62 kg N ha −1 . Significant yield increases were obtained from applied N up to the maximum rate of 101 kg ha −1 . The best estimate of yield ( Y ) plotted against N rate ( X ) was the linear equation Y = 3002 + 9.9 × ( R 2 =0.98). Kernels per spike increased and specific kernel weight decreased slightly with N application. There was no yield benefit from splitting the total applied N. Leaf rust ( Puccinia recondita Rab. ex Desm.) and powdery mildew ( Erysiphe graminis D.C.) infection showed a positive linear association with increasing N rate ( R 2 =0.77 and 0.42, respectively). Phosphorus fertilization decreased the incidence of both leaf rust and powdery mildew. Nitrogen, at the rates applied in this study, did not affect grain protein content but did increase total protein per hectare by increasing yield. Nitrogen fertilization increased the S content of grain and tended to decrease P and K content. Phosphorus and K had no effect on grain protein or mineral composition.