滴灌施肥中施氮量对两年蔬菜产量、氮素平衡及土壤硝态氮累积的影响

 【目的】研究滴灌施肥中传统施氮和减氮的处理对宁夏引黄灌区温棚两年蔬菜的产量、氮素平衡和硝态氮累积及淋洗状况的影响。【方法】试验于2004～2006年在宁夏引黄灌区日光温室条件下，以番茄-番茄-黄瓜-番茄四茬蔬菜为材料，研究滴灌施肥中的传统施氮和减氮两处理对宁夏引黄灌区温棚两年蔬菜的产量、氮素平衡和硝态氮累积及淋洗状况的影响。【结果】在前两茬传统施氮与增（减）氮两处理，对番茄的产量与吸氮量影响不大，在第三、四茬随着施氮量的下调，蔬菜果实产量、总吸氮量受到影响，第4茬番茄产量比第1茬下降了48.7～72.3 t?ha-1；不同施氮处理会造成对当季蔬菜收获后土壤表层0～30 cm NO3--N累积量高，在第4茬番茄收获后，在表层NO3--N累积量比第1茬下降了91.1%～92.2%，同时造成下茬蔬菜收获后土壤NO3--N累积量向下层运移，第2茬冬春茬番茄收获后，在60～90 cm土层NO3--N累积量比第1茬增加了105.4%～137.3%，在第3茬秋冬茬黄瓜收获后，90～120 cm土层NO3--N累积量比第1茬增加了4.8%～30.8%，而120 cm以下土层NO3--N累积变化不大；连续种植四茬蔬菜，有机肥也有向下淋失的可能。第4茬番茄收获后，在有机肥处理和有机肥后效处理中60～90 cm土层的NO3--N累积量比第2茬高22.7%；在黄瓜-番茄种植体系下，滴灌量及土壤表层水分含量对土壤溶液NO3--N含量有直接影响，表层土壤溶液中NO3--N有不断向下层淋洗的趋势，施氮量高的处理表现的更为明显；四茬蔬菜整个种植体系下氮素平衡，在氮素的总输入项中，以施氮量和灌溉水为主，总输入量随氮肥施用量的增加而增加，氮素输出项中以Nmin残留为主。【结论】在当地设施蔬菜滴灌施肥条件下，传统施氮量800 kg?ha-1过高并没有使当季蔬菜增产，造成当季蔬菜收获后土壤表层0～30 cm NO3--N累积量高，并对下茬蔬菜收获后有向下淋失的趋势影响，因此采取减量施氮是切实可行的。在有机肥和磷钾肥配施基础上，秋冬茬番茄氮肥推荐施用量在100～150 kg?ha-1、冬春茬番茄推荐施氮量在250～300 kg?ha-1、秋冬茬黄瓜氮肥推荐施用量在400～450 kg?ha-1。

Effects of Application of Nitrogen on Vegetable Yield, Nitrogen Balance and Soil Nitrogen Accumulation Under Two Years' Drip Fertigation

【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.