Nitrogen Utilize And Damnify As Well As Optimized Management Of Nitrogen Fertilizer Applied To Vegetable Field Of Greenhouse In Taihu Lake Region

This paper selects Yixing as experiment field, which is located Taihu lake region. We study greenhouse rotate crops of tomato and cucumber, on the basis of local farmer habitual dosage of nitrogen fertilizer, and take turns to decrease 20% nitrogen for 5 treatments [Tomato: 0 kg/hm2, 120 kg/hm2 (decrease N 60%), 180 kg/hm2 (decrease N 40%), 240 kg/hm2 ( decrease N 20%), 300 kg/hm2 ( farmer habitual dosage); Cucumber: 0 kg/hm2, 108 kg/hm2 ( decrease N 60%), 162 kg/hm2 ( decrease N 40%), 216 kg/hm2 (decrease N 20%), 270 kg/hm2 ( farmer habitual dosage)]. The present paper investigates the effects of different N levels on nutrients absorbability, accumulation of soil nutrients, yield and quality and nitrogen loss. Its objective is to obtain an N level which have high yeild, good quality and minimum pollution. Simultaneity, the process of salinization is also studied. These will provide science foundation to optimized management of nitrogen fertilizer applied to vegetable field of greenhouse cultivation. The main results are as follows:Decreased nitrogenous fertilizer has impact on nutrients absorbability of tomato and cucumber and accumulation of soil nutrients. compared with the 5 treatments, the treatment of decrease N 40% not only reduces the accumulation of nitrate in the soil, but also reduces the electric conductivity in the soil, and it also minimizes the fall of soil pH. On the basis of the treatment of decrease 40% N, increasing the dosage can not raise the accumulation of biomass of aboveground part. After two vegetable are being cultivated, the accumulation of nitrate in the soil of treatments of farmer habitual dosage is 292.3 mg/kg. EC value of greenhouse soil exhibites significantly positive correlation with soil NO3-N contents, total salt contents. After two vegetable are being cultivated, the soil of treatments of no nitrogenous fertilizer, decrease N 60% and decrease N 40% are suitable to cultivation, but the soil of treatments of decrease N 20% and farmer habitual dosage are becoming of salinization. The soil is applied nitrogen fertilizer, at the beginning, the soil pH become to uptrend, however, in the rotation clearance, soil pH become to evident downtrend. From the period of growing time, applying nitrogen fertilizer causes soil pH downtrend, the dosage of nitrogen fertilizer more much, the soil acidification more evident. The surface soil of treatments of decrease N 60%, 40%, 20% and farmer habitual dosage compare with cultivation before are fall about 0.75, 0.84, 0.92 and 0.97 unit, individually.Decreased nitrogenous fertilizer has impact on fruit yeild and quality of tomato and cucumber. The treatment of decrease N 60% significantly decrease the fruit yeild of tomato and cucumber, but there is no significant difference between decrease N 40% and farmer habitual dosage. The treatment of decrease N 40% not only ensures fruit yeild, but also increases economic benefit. The yields of two seasonal experiments are simulated by quadratic equation, the best quantity of applied of N are 241.6, 209.5kg/ hm2. Application quantity of N can reduce 30~40% in experimental region. Decreasing application of N can make fruit nitrate content declining. The tomato and cucumber fruit nitrate content of no nitrogenous fertilizer are 137.9 and 170.9 mg/ kg, farmer habitual dosage treatment are 406.1 and 328.8mg/ kg, individually. Decreasing with applying of nitrogen fertilizer, fruit Vc, soluble sugar content and organic acid content have waving change.Soluble sugar content of tomato fruit of decrease N 40% and decrease N 20% treatments are the highest, they increase 65.0,73.9%, compared with no nitrogenous fertilizer, but there are no significant differences between Farmer habitual dosage and CK. Vc, Soluble sugar content of Cucumber fruit of decrease N 40% treatment is the highest, and they increase 148.0,167.1%, compared with no nitrogenous fertilizer.The first way of nitrogen loss is leached, the second way is N2O emission. The way of leached loss of N is nitrate whereas ammonium leaching few. Application of N can evidently affect nitrate leaching, in the level of the experiment, the more applied of N the more nitrate leaching. In tomato and cucumber growing season, the nitrate leaching of apparent fertilizer N source of farmer habitual dosage treatment are 40.89, 105.89kg hm-2. because exposed the plastic film in prophase of cucumber growing season, fertilizer N leach greater than tomato season, the leaching rate is between 8.4% and 13.6%. quantity of application of N and drying- wetting soil process have effects on N2O emission. Applied 216 kg.hm-2 of N in cucumber field, N2O-N flux was 150.1μg.m-2.h-1, N2O-N cumulative emission was 2.82 kg.hm-2。...