Effect of N Topdressing and Slow-release N Fertilizer on Growth and Grain Weight of Buckwheat

Abstract

To verify the effect of slow-release nitrogen using organic fertilizers such as green manure, I investigated the weight of the stem, leaf and grain and their nitrogen contents in the plot with only urea (LP0), the plot with half urea plus half slow-release nitrogen fertilizer (LP1/2), and the plot with only slow-release nitrogen fertilizer (LP1). The stem, leaf and grain weights were greatest in LP0 at 23 days after sowing. At 68 days after sowing (at harvest), the growth was more vigorous in LP1/2 and LP1 than in LP0; the difference in growth was significant in LP1/2. At harvest, leaf SPAD values were significantly higher in LP1/2 and LP1 than in LP0, suggesting that the slow-release N fertilizer maintained a larger photosynthetic capacity until harvest. In LP1/2 and LP1, where the effect of the nitrogen fertilizer lasted until harvest, the grain weight and the nitrogen content of husked grains were higher than in LP0. This was considered to be the result of a combination of factors: the number of lateral branches and the number of flower clusters were large, and the seed-set percentage was high, which resulted in a large number of seeds per cluster. In addition, not only was the thousand-grain weight larger, but the husking ratio was also significantly higher.