Effects of Nitrogen Fertilizer and DCD on Cucumber Growth and Nitrate Leaching Loss from Soil in Greenhouse

Effects of applying different nitrogen fertilizer or water and DCD on cucumber yield,quality and nitrate leaching loss in soil were studied in greenhouse.The results showed that there was no significant difference in cucumber yield of the conventional water and nitrogen management and optimize water and nitrogen management,with sidedressed N input in comparison with conventional water and nitrogen management.Nitrate content in cucumber in optimize water and nitrogen management was significantly lower than that in W1N1.Furthermore,nitrate-nitrogen within 0-60 cm soil layers in optimize water and nitrogen management increased with more nitrogen fertilizer and water application,below 60 cm soil layer,nitrate-nitrogen content did not change significantly with cucumber growth.W2N2+DCD,W2N3+DCD,W2N4+DCD range over 6.09 to 33.36 mg/kg,19.03 to 29.28 mg/kg,14.98 to 25.46 mg/kg,respectively.It showed that adding DCD in nitrogen effectively suppressed nitrate-nitrogen leaching to deep soil layer.The order of nitrate-nitrogen accumulation in 0-180 cm soil layers was W1N1W2N3+DCDW2N2+DCDW2N4+DCDW1N0,consistently,during three cucumber growth periods.As applying nitrogen fertilizer and DCD,ammonia-nitrogen content was significantly higher than that of W1N1 in surface soil.W2N4+DCD decreased the N input and irrigation water by 56.88% and 33.30% in comparison with conventional water and nitrogen management.Compared with conventional water and nitrogen management,W2N4+DCD significantly reduced the risk of nitrogen leaching with 62.93%,74.42%,69.35% nitrate-nitrogen accumulation,respectively,in three cucumber stages.Overall,W2N4+DCD showed the best economic benefit and environmental benefit among different treatments.