Responses of natural 15N abundance in cauliflower (Brassica oleracea L. var. botrytis) and soil to the application of organic and chemical fertilizers

Abstract

Natural nitrogen isotope abundance (δ15N) has been suggested as a potential indicator for discriminating organic vegetables from their conventional counterparts. However, little is known about the δ15N characteristic of cauliflower (Brassica oleracea L. var. botrytis) under organic production and how the application of chemical fertilizers could affect this characteristic. In this study, δ15N characteristics of cauliflower (including the intra-plant δ15N characteristic) and soil under different fertilization treatments were investigated under field conditions. Five treatments were laid out: control, chemical fertilizers (F4M0), organic fertilizer (F0M4), and chemical fertilizer in combination with organic fertilizer at the ratio of 3:1 (F3M1) and 1:3 (F1M3). Results showed that plant δ15N was positively correlated with fertilizer δ15N and plant root/flower was more sensitive to changes of fertilizer δ15N and soil δ15N than leaf/stem. Distribution of δ15N in different plant parts (especially in flower and leaf) was significantly changed when organic fertilizers were partially or totally substituted by chemical fertilizers, suggesting a comparison of flower δ15N and leaf δ15N might be applicable for the organic identification of marketed cauliflowers. Our results provide fundamental data for the soil- and fertilizer-specific crop δ15N database and indicate that the intra-plant δ15N characteristic could be helpful for organic cauliflower identification.