Effects of different N rates on the yield, N use efficiency and fruit quality of vegetables cultivated in plastic greenhouse in Taihu lake region

Field experiments were carried out to study the effects of different N rates on the yield, N use efficiency and fruit quality of vegetables cultivated in plastic greenhouse, which of the soil used to be grown rice in Taihu lake region. Our results showed that under current cultivation conditions, fruit yields could still be ensured even at 40% deduction in nitrogen fertilizer input relative to the local farmer habitual usage. However, 40% reduction in N fertilizer input resulted in higher N use efficiency. In addition, improved fruit quality was achieved at reduced N fertilizer application. Nitrate contents of tomato and cucumber fruits with farmer habitual N usage were 406.1 and 328.8 mg/kg, respectively. Deduction of 40% and 20% in N input got similar soluble sugar content of tomato fruit that was significantly higher than the habitual N usage. Increased application of N fertilizer declined Vitamin C and soluble sugar contents of cucumber fruits. In conclusion, under current cultivation conditions, high fruit yields and quality can be ensured at 20%–40% reduction in habitual N input, which presents a possible scale to a safety and efficient N fertilizer usage in greenhouse farming system.