Effects of Nitrogen Fertilizer and Planting Density on Yield Loss Percentage of Mechanical Harvesting in Rapeseed

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In this study, Huayouza 62 was planted by direct-seeding with three nitrogen(N) fertilizer levels(120, 180, and 240 kg N ha–1) and three planting densities(15×104, 30×104, and 45×104 plant ha–1). The yield loss percentages of mechanical harvesting were investigated when the moisture contents in seeds ranged from 10.86% to13.17%. The results showed the total yield loss percentage was from 6.13% to 7.82% in different treatments. There existed differences in the ratio of the yield loss in different parts to the total yield loss. The ratio of the yield loss caused by shattering(SL) to the total yield loss was the least in different treatments, ranging from 2.41% to 3.90%. The ratio of the yield loss caused by combine header(CHL) to the total yield loss ranged from 17.99% to 21.99%. The ratio of the yield loss caused by cleaning and threshing(CTL) to the total yield loss ranged from 74.15% to 79.52%, among which the yield loss caused by mixed straw and shell(ML) was the main part(from 65.51% to 69.05%), and the yield loss caused by non-threshing pod(NTPL) was low with the range from 8.64% to 10.47%. The plot yield increased with increasing N application rates and planting densities. The total yield loss percentage had extremely significantly positive correlation with plot yield(r = 0.970**) and N fertilizer(r = 0.918**), and no significant correction with planting density(r = 0.358). The results of this study indicated that in the rapeseed mechanical production, appropriate N fertilizer and planting density should be applied for high yield, and then the yield loss percentage should be reduced on the basis of high yield.