Preharvest Sprouting of Hard Winter Wheat as Affected by Nitrogen Nutrition1

Abstract

Preharvest sprouting seriously reduces milling and baking quality of hard winter wheat (Triticum aestivum L.) grain. Nitrogen fertilization is used to increase grain yield and protein content, but its effect on preharvest sprouting is unclear. To determine the effect of nitrogen nutrition on preharvest sprouting, five wheat genotypes differing in susceptibility to sprouting were grown in sand with nutrient solution. Differential N regimes were imposed by leaching nutrients from one set of plants at early boot stage (Feekes scale 9), after which complete nutrient solution or solution devoid of N was used until plants were mature. Grain dormancy was assessed 15 days after physiological maturity by treating spikes with simulated rain. Grain from control (no simulated rain) spikes had no preharvest sprouting and low a‐amylase activity in all genotypes. Simulated rain did not cause preharvest sprouting or increase a‐amylase activity in highly resistant genotypes ‘Clark's Cream’ and ‘Lancota’, but increased preharvest sprouting and a‐amylase activity in susceptible genotypes KS75216 and ‘Parker 76’. High N fertility increased absolute α‐amylase activity but not specific α‐amylase activity (activity • mg N−1). We concluded that high levels of fertilization increase rain‐induced preharvest sprouting in genotypes with moderate or low levels of resistance. Nitrogen fertilization probably would not affect preharvest sprouting of genotypes with strong resistance and all genotypes in areas where conditions are not conducive to preharvest sprouting.