Utiliaztion and fate of nitrogen in greenhouse vegetable under optimized nitrogen fertilization

Excessive nitrogen (N) fertilization input has resulted in fertilizer waste and soil quality degeneration, etc. Based on the last 3-year results of the effects of different N fertilizer management models on soil agronomy, fertilizer and environment efficiency, an optimum N fertilizer management model was selected. To indentify the model and investigate the fate and utilization of the chemical N fertilizer, a microplot experiment with 15N tracing technique was carried out in Shouguang, Shandong Province, which is the famous greenhouse vegetable production base in Northern China. The experiment included the conventional N fertilizer model (FP) and optimized N fertilizer model (OPT). The main findings are that the higher dry matter production and N content are obtained in the OPT model and only about 20% of N uptake of plants comes from chemical N fertilizer. Compared with the FP model, the agronomic efficiency and N recovery efficiency of chemical fertilizer N are significantly increased in the OPT model. NO-3-N is the main chemical N residue form, and theNO-3-N accumulation amounts in 0-100 cm soil layer of the two models are N 536.9 and 340.3 kg/ha respectively.NO-3-N is mainly accumulated in 0-40 cm soil layer, and NO-3-N accumulation amounts are decreased with the increase of soil depth. Compared with the FP model, soilNO-3-N accumulation amounts in each soil layer of the OPT model are significantly decreased. 32.4% and 8.2% of 15N loss are from the chemical N fertilizer, respectively in the FP and OPT models, and the N loss rate of the OPT model is 24.2% lower than that of the FP model. The present study shows that the OPT model can improve chemical N fertilizer uptake and utilization, reduce chemical N fertilizer loss and maintain the sustainability of greenhousebased intensive vegetable systems.