Abstract: 【Objective】The effects of different application nitrogen treatment were studied on soil NO3--N accumulation and Nitrate leaching in different soil depth in Ningxia yellow river irrigated area. The anniversary vegetable yield and nitrogen balance of tomato-tomato-cucumber-tomato growing system were estimated. as The purpose was to provide a firm foundation for better reasonable nitrogen application of tomato-tomato-cucumber-tomato growing system under drip-irrigation condition of greenhouse in the area.【Method】The representative tomato and cucumber were chose in the area. A method with field experiment and chemical analysis was carried out .To compared with CK and Organic fertilizer ,the effects of different application nitrogen treatment were studied on the nitrogen balance, nitrate accumulation and leaching with tomato-tomato-cucumber-tomato growing system under drip-irrigation condition in greenhouse in Ningxia yellow river irrigated area from 2004 to 2006. 【Result】 Preceding two season ‘s tomato yield and total assimilated N were not increased in convention application nitrogen and high application nitrogen treatment, but medium and low of two application nitrogen treatment maintenance upper yield. After two season’ vegetable, with the increasing application nitrogen, vegetable’s yield and total assimilated N were increased in decreased application nitrogen condition. After any season vegetable harvesting, all of nitrate accumulation was very high with middle or high nitrogen rate. The NO3--N accumulation amount in 0~90 cm were 73%~75% in total NO3--N accumulation amount in 0~180 cm.. With decrease application nitrogen amount, the soil NO3--N accumulation 177.1~651.6 kg•ha-1 was reduced 15.8~50.5 kg•ha-1 from the first season to fourth season in different treatment, but then content NO3--N of soil solution were leaching in the main 60~90 cm depth. The application nitrogen and irrigation water were main place in nitrogen input, the nitrogen input was increasing significantly with nitrogen fertilizer increasing. The soil Nminresidue was main place in nitrogen output, shoot nitrogen uptake (697.7~882.1 kg•ha-1) of each season vegetable didn’t increase significantly with nitrogen input increasing, therefore, which caused soil Nmin accumulation a lot with high nitrogen rate. 【Conclusion】Some factors of nitrogen balance, nitrate accumulation and nitrogen balance were discuss, reduced nitrogen fertilizer was feasible with tomato-tomato-cucumber-tomato growing system under drip-irrigation condition in the area. The based on Organic fertilizer rate 、 phosphor nitrogen fertilizer and potass fertilizer rate condition, the nitrogen fertilizer rate was about 100~150kg•ha-1 under autumn-winter season ‘s tomato, the nitrogen fertilizer rate was about 250~300kg•ha-1 under winter-spring season’s tomato, the nitrogen fertilizer rate was about 400~450kg•ha-1 under autumn-winter season's cucumber. As result maintain vegetable’s yield and satisfaction above nitrogen demand did not cause environmental threaten.

Key words: Tomato, Cucumber, Drip-irrigation, NO3--N, Nitrogen balance