Effects Of Different Fertilizer On δ¹⁵N Of Tomato And Lettuce

In recent years, the organic agriculture developed rapidly, but there are no reliable methods todetect the use of fertilizers. In this study, we planted tomato by pot cultured and lettuce under conditionsof the field.8treatments were laid out in tomato experiment and4in lettuce experiment. Theexperiments were conducted at2012in institute of agricultural of Shunyi District, Beijing. To develop atool that can be used to fingerprint the use of fertilizers, we examined the temporal variation of δ¹⁵N ofsoil, tomato and lettuce applied with different N fertilizers. The results show that:（1）The δ¹⁵N of soil applied with compost was1.09%higher than the control treatment in tomatoexperiment, while the δ¹⁵N of soil applied with urea was at least0.73%lower than the controltreatment（P＜0.05）. In lettuce experiment, the δ¹⁵N of soil was also enriched by the application ofcompost, while decreased by the application of urea. At50DAT, the δ¹⁵N of soil applied with compostwas0.87‰higher than the control treatment, and the δ¹⁵N of soil applied with urea was2.15‰lowerthan the control treatment（P＜0.05）.（2） The δ¹⁵N of tomato leaves and tomato fruit increased by the application of compost, whereasdecreased by urea. The range of δ¹⁵N of leaves and fruits sampled from the compost treatments were6.02‰¹2.75‰and4.69‰⁸.24‰, while the corresponding range of the urea treatments were2.83‰⁵.53‰and2.66‰⁴.50‰.（3） The δ¹⁵N of lettuce increased by the application of compost, whereas decreased by urea. Theδ¹⁵N of lettuce was9.54‰from the compost treatment, while the range of δ¹⁵N of lettuce from thecompost treatments was2.57‰³.75‰. The difference of δ¹⁵N between compost treatment and ureatreatments was5.79‰⁶.99‰.（4） The ranking result of δ¹⁵N of different tomato parts was old leaf> new leaf> new stem> fruit>old stem> lateral root> taproot.15N gradually enriched with the process of absorption, transportationand distribution of nitrogen. The δ¹⁵N of inner part of lettuce was significantly higher than root, whilethe δ¹⁵N of outer part of lettuce was significantly lower than root（P＜0.05）.（5） The boundary point of δ¹⁵N of tomato fruit between compost treatments and urea treatmentswas5‰, and the corresponding boundary point of lettuce was9.54‰. Similar boundary point should beset to inspect organic produce.