Effects of different nutrition management on vegetable growth and runoff characteristics of soil nitrogen in perennial vegetable field

【Objectives】A widespread phenomenon of excessive application of chemical fertilizers in vegetable production is observed, which has caused serious nonpoint pollution problem. To reduce transformation losses of field nitrogen nutrient imposing pollution potential risk on water bodies, it is necessary to study a set of fertilization technology and determine applications threshold of fertilizers in vegetable production. 【Methods】A plot experiment with treatments of different combinations of organic and inorganic fertilizers was conducted in a perennial vegetable field. There were seven treatments, control(CK)and organic manure(OM)combined with different rates of inorganic fertilizers i.e. no fertilization of inorganic nitrogen(N0), conventional fertilization(CON), optimum fertilization(OPT), nitrogen addition upon OPT level(OPT+N), phosphorus addition upon OPT level(OPT+P), synchronous addition of nitrogen, phosphorus and potassium upon OPT level(OPT+NPK). The aim of this experiment was to investigate effects of different nutrition management on growth of crops and nitrogen runoff from vegetable field with ball cabbage, eggplant and ball cabbage mode.【Results】A total of eighteen runoff samples in different treatments were collected during a three-successive vegetable growth period in a year. During the whole experimental period, the concentrations of NH+4-N in different treatments were all lower than 2.0 mg/L, meeting the grade V national surface water quality standard. No fertilization-induced influence was observed on NH+4-N concentration. The runoff concentrations of NO-3-N and total nitrogen in different treatments were 0.03-28.43 mg/L and 1.06-31.79 mg/L, respectively. Nitrate nitrogen was considered as the main form of mineral nitrogen in runoff water of vegetable field, and similar runoff characteristics in concentrations of NO-3-N and total nitrogen were observed. The fertilization increased the concentration of NO-3-N and total nitrogen in runoff water and a more pronounced effect was recorded in inorganic fertilizer as compared to organic manure. The concentrations of total nitrogen in different treatments were almost exceeded the grade V(2.0 mg/L)national surface water quality standard during the whole experiment time. Compared to other treatments, the highest total nitrogen concentration and off-grade of NO-3-N concentration in the treatment of OPT+NPK were observed. The annual runoff loads of total nitrogen in the control was 30.8 kg/hm2 and there was no significant difference between the N0 and CK treatments. The runoff loads of total nitrogen in the treatments of CON, OPT, OPT+N, OPT+P and OPT+NPK were 69.81, 54.95, 76.6, 55.45 and 90.73 kg/hm2, respectively, which were increased by 127%, 78%, 149%, 80% and 195% compared to the control. Moreover, the highest nitrogen load of 90.73 kg/hm2 was recorded in the OPT+NPK treatment and a lower nitrogen load of 54.95 kg/hm2 was observed in the treatment of OPT. The runoff coefficients of nitrogen in the fertilizer treatments were from 1.47% to 3.44% and showed an increasing trend with the increase of the fertilizer application amount. The fertilization increased the vegetable yields markedly, and the yields of ball cabbage and eggplant are increased by 67.5% and 114.2% in the N0 treatment compared to the control, whereas the increases in other treatments were 5.1-5.5 times and 4.5-5.9 times of those of the control. The combined application of chemical nitrogen, phosphorus and potassium fertilizers based on application of same level of organic manure showed more significant increases in the vegetable yields. The highest vegetable yields were also recorded in the OPT+NPK treatment which represented the highest input of chemical fertilizers. 【Conclusion】 From the economic and environment perspectives, the fertilization of the OPT treatment should be considered as a recommendation in vegetable production as comprehensive analyzing the vegetable yields, fertilizer costs and runoff load of total nitrogen.