露地栽培条件下大白菜氮肥利用率与硝态氮淋溶损失研究

以我国北方主要蔬菜作物———大白菜(Brassica.penkinensis)为研究对象,利用渗滤池研究了露地栽培条件下不同供氮水平对氮肥利用率和硝酸盐淋失的影响。结果表明,施有机肥(折N120kg/hm2)的增产效果显著,不会造成硝态氮向下层土壤剖面淋溶和增加硝态氮的淋洗损失,有机肥N的利用率达25%。在有机肥的基础上施用化学氮肥的增产效果不明显,3个化学氮肥用量(375、750和1125kg/hm2)处理下VCR(产投比)值均低于2.0,而且随氮肥用量增加土壤剖面硝态氮残留量呈线性递增;渗滤池1.3m处的硝态氮淋失量分别为16.6、21.0和37.6kg/hm2,呈指数增加;氮肥表观淋失率为2.3%、1.8%和2.6%,氮肥利用率分别为7%、2.9%和2.6%,氮肥表观气态损失率分别为25.4%、37.5%和40.5%。总的来看,露地大白菜施肥水平偏高,氮肥利用率偏低,环境风险较大。

Study on N use efficiency of chinese cabbage and nitrate leachingunder open field cultivation

Fate of nitrogen fertilized on chinese cabbage(Brassica penkinensis) in open field of vegetable especially leaching loss was studied by lysimeter. The results showed that the yield of chinese cabbage application of organic manure (equivalent N 120 (kg/hm~2)) was much higher than CK, and nitrate concentration no difference in lower soil profile, the leaching loss of nitrate from 1.3m depth of lysimeter was also not increased. Whereas, on the based of organic manure, the yield was not increased remarkably with chemical N fertilization and the VCR(value-cost ratio) was lower than 2.0. On the other hand, with increasing of N rate, the residue of nitrate in soil profile rose linearly and nitrate leaching loss from 1.3m depth lysimeter went up exponentially. For the three rates of chemical fertilizer N 375, 750 and 1125 (kg/hm~2), nitrate leaching loss was N 16.6, 21.0 and 37.6 (kg/hm~2),the apparent fertilizer N leaching loss rate was 2.3%, 1.8% and 2.6%, apparent fertilizer N use efficiency was 7.9%, 2.9% and 2.6%, apparent fertilizer N loss by air was 25.4%, 37.5% and 40.5%,respectively. These results indicated,the rate of N fertilization in open field of vegetable was much higher which might give higher pressure on environment.