Effects of different N rates on nutrients accumulation,transformation and yield of summer maize

Rational N fertilization could improve the yield and quality of crop production,but over-application may cause groundwater and atmosphere pollution. Based on the characteristics of N,P,K uptake,accumulation and transformation, applying fertilizer at appropriate time and dose can increase crop yield and nitrogen use efficiency.A summer maize field experiment was carried out in high fertility soil of Guanzhong of Shaanxi province in 2004 to investigate effects of N fertilization on biomass,yield,accumulation dynamic of N,P and K,N use efficiency and nutrient transformation.The experiment design was the randomized complete block with four replications.The area of each plot was 33.6 m2(6m5.6m).Four nitrogen fertilization levels were employed including 0,125,250 and 375 kg/ha,one third of nitrogen fertilizer and total P(P 45 kg/ha) and K(K 216 kg/ha) was used as basal fertilizer,and two third of nitrogen fertilizer used as topdressing fertilizer at ear premordia stage.The results showed that N application rates affected the nutrient accumulate at different growth stages,but no influence on the tendency of nutrients accumulation in plant.Biomass and N,P and K accumulate increased with the prolongation of growth stages,and the accumulation tendencies were very similar,and could be described by S curve. The grain yield of different treatments was ranged from 7000 to 7700 kg/ha.The yield of treatment N250 was significant higher than other treatments,among which no significant difference on yield was observed.Fertilizer N recovery ranged from 10% to 18%,which decreased slightly with increasing of N rates.N application could increase N accumulation in grain,but the effect on P in grain was neglected.N transfer amounts,transfer efficiency and its proportion in grain decreased with increasing of N application rates,P transformation showed the similar tendency at different N fertilization.Comprehensive the yield, fertilizer N recovery,nutrients transformation and environment pollution,the recommendation of fertilizer N rate for summer maize was less than 125 kg/ha in the experimental area.