Effects of humic acid compound fertilizers on the nitrogen utilization and effects on the following rape

Effects of different amounts of humic acid(HA) compound fertilizer on the yield and N utilization of rape(Brassica campestris L.ssp.chinensis L.Makino)were studied under an experimental condition.Theresults show that HA compound fertilizer can enhance the yield of rape.The relationship between fertilizer application amount and yield of rape can be described with a quadratic curve regression model.The yield of the rape indicates that HA compound fertilizer is slow-releasing with long efficient period and high-nutrient-utilization-ratio.Nitrate reductase activity changes as a shape“S”and its peak is at 600kg/hm² application amount of HA,but the peak of NO^-₃-N content is at 1200kg/hm².HA compound fertilizer increases the absorption and utilization ratio of N in rape,and improves the N nutrient in soil.