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

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

【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48.7～72.3t·ha-1;不同施氮处理会造成对当季蔬菜收获后土壤表层0～30cmNO3--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60～90cm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,90～120cm土层NO3--N累积量比第1茬增加了4.8%～30.8%,而120cm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60～90cm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800kg·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0～30cmNO3--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100～150kg·ha-1、冬春茬番茄推荐施氮量在250～300kg·ha-1、秋冬茬黄瓜氮肥推荐施用量在400～450kg·ha-1。

[Objective] Effects of conventional application of N and reduced application of N on vegetable yield and nitrogen balance and nitrogen accumulation and nitrate leaching under two years＇ drip fertigation in irrigation areas by diverting water from Yellow Rriver of Ningxia were studied. [ Method ] The experiments under greenhouse conditions were conducted with tomato-tomato- cucumber-tomato planting system from 2004 to 2006. [Result] The first two season＇s tomato yield and total assimilated N were not increased in the conventional application of nitrogen and increased/decreased application of nitrogen treatment. After two seasons, with the decrease of application of nitrogen, the tomato＇s yield in fourth season decreased by 48.7-72.3 t.ha^-1 compared with the yield in the first season, with the increasing application of nitrogen, the vegetable yield and total assimilated N were increased. Over application of nitrogen caused high accumulation of NO3^--N within upper soil（0-30 cm） after first season tomato harvest, the NO3^--N accumulation within upper soil after the fourth season harvest were reduced by 91.1%-92.2% compared with after first season harvest. Different application of nitrogen at different rates caused soil NO3^--N accumulation moving down. NO3^--N accumulation within 60-90 cm soil after the second tomato harvest increased by105.4%-137.3% compared with that after the first tomato harvested. Compared with that after the first tomato harvest, the NO3^--N accumulation within 60-90 cm soil increased by 4.8%-30.8% after the third cucumber harvest, but the soil NO3^--N accumulation under soil depth 120 cm changed a little. It was possible that the organic fertilizer moved down after four seasons of vegetable planting. Under the treatment of organic fertilizer, compared with that after second tomato harvest, the NO3^--N accumulation within 60-90 cm soil increased by 22.7% after the fourth tomato harvested. Under the planting system of cucumber-tomato, dripping amount and the content of upper soil （0-30 cm） water made a significant difference to NO3^--N in soil solution. The NO3^--N of soil solution in upper layer （0-30 cm） could leach down, especially in the application of nitrogen treatment. The application of nitrogen and irrigation took the main place in nitrogen input, the soil Nmin residue took the main place in nitrogen output. [Conclusion] Under the condition of drip fertigation in vegetable planting in greenhouse, season＇s vegetable yield in conventional application of N （800 kg.ha^-1） were not increased and caused high accumulation of NO3^--N in upper soil layer （0-30 cm） after first season vegetable harvest and caused soil NO3^--N accumulation moving down after next vegetable harvest, it is feasible to reduce nitrogen application. Based on organic fertilizer and phosphor （P） nitrogen fertilizer and potassium （K） fertilizer, the nitrogen fertilizer application was about 100-150 kg.ha^-1 for autumn-winter season tomato, about 250-300 kg.ha^-1 for winter-spring season tomato, about 400-450 kg.ha^-1 for autumn-winter season cucumber.