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为了证明利用氮稳定同位素技术鉴别有机蔬菜的可行性,本试验研究了不同肥料条件下土壤和莴苣不同部位的同位素特征变化情况。设置4个不同肥料条件:撒施有机肥(N 400 kg·hm-2)、局部施尿素(N 300 kg·hm-2)和撒施尿素(N 400 kg·hm-2),以及对照(不施用任何肥料)。结果表明不同肥料条件下土壤15N丰度(即δ15N)差异显著(P<0.05),表现为撒施有机肥>对照>局部施尿素>撒施尿素。各肥料条件下土壤δ15N值均呈现先升高再降低最后趋于平稳的变化规律,峰值出现在定植后20 d。不同处理莴苣δ15N值的差异及变化规律与土壤δ15N值变化规律相同。莴苣不同部位δ15N值比较结果为:外叶>根>内叶。莴苣内部同位素特征受环境影响最迅速。总体上,莴苣内叶和土壤的δ15N变化可以反映施肥情况,从而可对判断有机蔬菜种植过程中氮肥的施用种类提供依据。
In order to prove the feasibility of using nitrogen stable isotope techniques to identify organic vegetables, this experiment studied the changes of isotope characteristics of different parts of soil and lettuce under different fertilizer conditions. Four different fertilizer conditions were set up: N 400 kg · hm-2, N 300 kg · hm-2 and N 400 kg · hm-2, Do not apply any fertilizer). The results showed that the soil 15N abundance (ie, δ15N) was significantly different under different fertilizers (P <0.05), showing organic manure application> control> topical application of urea> application of urea. The soil δ15N values of all kinds of fertilizers showed the first increase and then the last change trend, and the peak appeared at 20 d after planting. The differences and variations of δ15N between different treatments were the same as those of soil δ15N. Δ15N values of different parts of lettuce were compared as follows: outer leaf> root> inner leaf. The internal isotope characteristics of lettuce are the most affected by the environment. In general, δ15N changes in the leaves and soil of lettuce can reflect the application of fertilizers, which can provide a basis for judging the application of nitrogen fertilizers in the growing process of organic vegetables.