Effects of nitrogen topdressing timing on yield and grain protein content of 'yumeshihou' wheat

Abstract

In two growing seasons (2008-09 and 2009-10) we applied nitrogen topdressing every 1 to 2 weeks from stem elongation to ripening, and examined the effects on yield, grain protein content, and dry matter and nitrogen accumulation in the spikes after anthesis in 'Yumeshihou' wheat. Topdressing at the stem elongation stage about 16 days before anthesis, and that at the mid-grain-filling stage about 20 days after anthesis tended to increase the yield in both growing seasons. The topdressing at about anthesis did not increase the yield owing to a decrease in grain number per spike. Dry-matter accumulation after anthesis was increased by topdressing at the stem-elongation and mid-grain-filling stages. Grain protein content was increased by topdressing at anthesis to ripening stage but not by topdressing at the stem elongation stage. The lack of increase in grain protein content in the plants topdressed at the stem elongation stagewas attributed to an increase in dry matter accumulation before and after anthesis as well as nitrogen accumulation in the spikes. Topdressing after anthesis signifcantly increased in grain protein content in plants because nitrogen accumulation in the spikes was greater than the dry matter accumulation after anthesis.