2017 Volume 86 Issue 4 Pages 382-387
In Yamaguchi Prefecture, nitrogen topdressing is commonly applied at the flowering stage to maintain appropriate grain protein content (GPC) in the bread wheat cultivar “Setokirara”. We examined whether it is possible to replace nitrogen topdressing, such as ammonium sulfate at the flowering stage, with the application of a coated urea fertilizer at the spikelet formation stage. A field experiment was conducted in 2013/2014 and 2014/2015 at the Yamaguchi Prefectural Agriculture and Forestry General Technology Center. The GPC of “Setokirara” treated with coated urea at the spikelet formation stage was lower than that of “Setokirara” treated with ammonium sulfate at the flowering stage. In contrast, the yield of “Setokirara” treated with coated urea was higher than that of “Setokirara” treated with ammonium sulfate. The GPC of “Setokirara” was significantly correlated with yield. Nineteen to sixty percent of nitrogen was released from the coated urea fertilizer before the flowering stage. In contrast, the amount of nitrogen released from coated urea fertilizer was low around the flowering stage, which is known to be the most effective period to apply nitrogen topdressing for an increase in GPC. This may be why “Setokirara” treated with coated urea had a higher yield and lower GPC. Even when the dose of the coated urea fertilizer applied was doubled, the GPC of “Setokirara” remained lower than that of “Setokirara” treated with ammonium sulfate at the flowering stage.
