Nitrogen fertilizer optimization strategy for greenhouse cucumber production in Beijing suburbs

ObjectivesExcessive fertilization, lower nitrogen use efficiency, high nitrogen residual and higher nitrate content are common in facility vegetables cucumber in Beijing suburbs. The objective of this study was to research the reasonable nitrogen application rate for higher yield, better quality of vegetable, lower residual nitrogen in soil and much better environmental benefits.

MethodsField plot trail was adopted in this experiment and cucumber cultivar Jinpei 98 was used as test material. Five different N levels were set up:0, 120, 240, 360, 480 kg/hm². The cucumber yield, quality, nitrogen residue, economic benefits and the nitrogen balance under different N applications were investigated.

ResultsCompared with no N application treatment, the cucumber yield in all the other treatments were significantly improved with the highest yield at N rate of 360 kg/hm². The nitrogen residual amount was increased with the increasing of nitrogen application rate. The nitrate contents in cucumber were also increased, and exceeded the nitrate critical level at N rate of 480 kg/hm². The content of soluble sugar increased first and then decreased with the increasing of N application rate and the content of soluble sugar was the highest at 360 kg/hm². The nitrogen content of cucumber increased with the increasing of N application. Compared with no N treatment, the nitrogen content of cucumber in treatments with N 240, 360 and 480 kg/hm² was significantly increased (P < 0.05), but the nitrogen content of treatment with N 480 kg/hm² was lower than the treatment with N 360 kg/hm². The application of nitrogen fertilizer had no significant effect on phosphorus, potassium content (P>0.05). Under different nitrogen application conditions, the nitrogen utilization efficiency was between 4.9%-24.9% and the nitrogen retention rate was between 24.5%-58.0%. Nitrogen utilization efficiency was the highest, residual rate was the lowest when the nitrogen application rate was 240 kg/hm². The loss of nitrogen was increased with the increasing of nitrogen application, the loss of nitrogen in the treatment with N 360 kg/hm² was lower than treatment with N 240 kg/hm².

ConclusionComprehensive consideration of the relationship between soil environment effect and yield under the tested soil condition, the recommended N application rate was 341.7 kg/hm², and the maximum yield was 78.4 t/hm². To obtain the best economic benefits, the nitrogen application rate was 329.6 kg/hm².