Effect of nitrogen, phosphorus and potassium combined application on dry matter accumulation, yield and economic benefits of adzuki bean

To explore optimum fertilizer application levels of nitrogen, phosphorus and potassium, the '3414' fertilizer experiment was conducted to study the effects of combined application nitrogen (N), phosphorus (P) and potassium (K) combined application on dry matter accumulation, yield and economic benefits of summer adzuki bean. By analyzing the interaction effect of fertilizer factors, a ternary quadratic model was established with fertilizer application levels as variables dry matter accumulation, yield and well as economic benefits as objective functions. Results showed that the mean value of dry matter accumulation and the mean value of yield of 13 fertilization treatments were 1.26 and 1.17 folds that of no fertilization treatment, respectively with significant differences (P < 0.05). Compare with no fertilization treatment, excessive N fertilization and decrement N fertilization had lower economic benefits, while excessive K fertilization had no significant difference, and the other treatments had higher economic benefits by average 11.05%. With the increase of nitrogen, phosphorus and potassium application, the dry matter accumulation, grain yield and economic benefits first increased and then decreased. The influence factors followed the order of as N > P > K for dry matter accumulation and N > K > P for grain yield. Each decrement fertilization had the highest agronomic use efficiency. The fertilization of N, P and K had interaction effect: N and P as well as N and K both had positive effect on dry matter accumulation, grain yield and economic benefits: P and K had positive effect on dry matter accumulation and negative effect on grain yield and economic benefits. Through integrated optimizing of dry matter accumulation, grain yield and economic benefits, and the model screening, the results showed that the optimum combination for dry matter accumulation ≥ 6500 kg · hm^-2, yield ≥ 2350 kg · hm^-2, economic benifits ≥ 17800 yuan · hm^-2 were N 67.6 ∼ 76.4 kg · hm^-2, P₂O₅ 85.8 ∼ 105.0 kg · hm^-2, K₂O 52.5 ∼ 67.5 kg · hm^-2, respectively, and their proportion for N : P₂O₅ : K₂O was 1 : 0.99 : 0.75. This study provided theoretical supports on fertilizer utilization economically and efficiently for summer adzuki bean production. (authors)