Effects of Different Fertilizations on the Nitrate Contents in the Fruits and Soil of Greenhouse Cherrytomato

The effects of different fertilizations(different fertilizers and their rate combinations) on the nitrate contents of the fruits and soil of cherrytomato were studied.The results denoted that the nitrate contents in cherrytomato fruits gradually increased with the topdressing frequencies and reached their peaks in the middle harvesting period,and finally came to a slightly increased content;the nitrate and nitrite contents in the fruits were 49.6～273.0 mg·kg~(-1),and 0.011～0.054 mg·kg~(-1),respectively.After the fourth topdressing,the nitrate contents in the fruits and soil(0~40 cm soil) peaked 6~9 days after the fourth topdressing and then began to decline.The accumulative nitrate amount in the fruits appeared to significantly correlate to the nitrate content in the soil.So proper nitrogen fertilizer rate cannot lead to extreme nitrate accumulation in the fruits;the fertilization of organic fertilizers in combination with proper amount of chemical fertilizers is conductive to improving fruit quality and yield and down-regulating soil nitrate content.