Integrated nitrogen management in greenhouse tomato production

Field experiments were conducted in a greenhouse of Shouguang,Shandong province to validate integrated nitrogen management and PSNT(Presidedress Soil Nitrate Testing) techniques in monitoring nitrate dynamic in root zone and corresponding recommendation of sidedressing N fertilizer for greenhouse tomato in spring and autumn seasons in 2004.Considering the target yield level,FW 84 t/ha,in spring,the rate of N supply(soil NO3--N in root zone + N through irrigated water + sidedressed N) were N 300 kg/ha of each sidedress at the first,second and the third cluster fruit expanding stage(CFES),and N 200 kg/ha in the later growing stage.Similarly,when the target yield was FW 75 t/ha,in autumn,the rate of N supply were N 200 kg/ha of each sidedressing at the first,second third and the fourth CFES,and N 250 kg/ha in the later growing stage in autumn season.Including organic manure application as conventional way,optimized N treatment reduced N application rate by 62% and 78% of total N fertilizer in spring and autumn season,respectively,compared to conventional treatment,because environmental N(N released from organic N pool and N from irrigated water etc.) contributed considerable N to tomato growth.Compared to conventional N treatment,apparent N loss in soil-vegetable crop system significantly reduced in optimized N treatment while the yield was the same as that of conventional treatment.It was concluded that integrated nitrogen management,together with PSNT technique,was very useful in increasing nutrient efficiency and reducing the risk of environmental pollution.