摘要:
应用15N同位素示踪技术,研究了红萍氮素被鱼体摄食后,再以排泄物肥田,对水稻生长以及氮素吸收情况。试验结果表明,红萍作饵料对尼罗罗非鱼生长有良好效果。在稻萍鱼体系中,经2个早季稻田放养表明,每季鱼体可增重41.2～48.0%。投施红萍作饵料,以萍喂鱼,鱼体排泄物肥田,对水稻生长有益。稻谷产量比不施氮肥的对照区高9.7～20.7%,而直接压施等氮量红萍作肥料处理,则高于对照区4.4～14.8%。在稻萍鱼体系中,萍体氮素可多次利用,15N标记红萍作饵料喂养尼罗罗非鱼后,鱼体含氮量可达2.41%,其15N丰度值可从0.366%提高到0.4313%,能有效的将植物蛋白转化为动物蛋白,鱼体的15N利用率为38.24%,而水稻对鱼粪中15N利用率为29.52%,其15N总利用率可达67.76%。而直接压施红萍作肥料其15N利用率为48.83%。
Abstract:
In the rice-azolla-fish cropping system as we tested after azolla had been eaten by fish, the effect of fish’s excreta for rice growth and nitrogen uptake were studied with 15N isotope labelled method. Results of experiment in the paddy fields showed that azolla was a good fodder to fish (T,nilotica). Its weight increased 41.2-48.03% during early rice season, there azolla(60 kg/ha) was put into rice-azolla-fish system as the fish’s fodder.After that, the excreta also fertilized the paddy soil and had a good effect to rice growth so the rice yield increased 9.7-20.7% than that of check (without application of N-fertilizer), but azolla (60kg/ha) was incorporated as green manure in paddy soil the rice yield only increased 4.4-14.8% as compared with check. we found azolla-N could be utilized for several times in rice-azolla-fish. First the nitrogen content of fish reached 2.41% and 15N excess was changed from 0.366% to 0.4313%. So the protein of plant was changed into animal protein effectively during early rice seaeon. Second, the rates of 15N recoveried by fish and rice were 38.24% and 29.52% respectively, there fore the total rate of 15N utilized was 67.76% in the 15N isotope labelled azolla as fish fodder and that was higher than the average rate of N utilized in azolla incorporated as green manure. The later was 48.83%.
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