Intercropping affects glucosinolate content in broccoli

Summary

Numerous studies proposed that the protective effect of cruciferous vegetables against cancer may be due to their relatively high content of sulfur-containing glucosinolates. Nitrogen (N) and sulfur (S) application significantly affect glucosi¬nolate concentration in plants. Total S requirement differs between crop species; in general S demand of Cruciferae is high. S supply has an impact on the total glucosinolate concentration but also on the relative proportions on the individual glucosinolates. Investigations showed that in broccoli plants, total glucosinolate concentrations were high at insufficient N supply, independent of the S level. This study aimed to improve the nutritional value of broccoli (Brassica oleracea var. italica) by intercropping. A competitive broccoli-lettuce intercropping system were designed in order to assess how the single intercrop component species utilize and compete for N and S resources and how these dynamics are altered in response to changes in nutrient availability. Lettuce expected to reduce the available N for broccoli without influence S availability. The first experiment consisted of 6 treat¬ments, combinations of two levels of N (90 and 220 kg×ha-1) fertilization and three cultivation systems (broccoli–lettuce intercropping, sole broccoli and sole lettuce). In the second experiment also two levels of S (0 and 65 kg×ha-1) were included and the total number of treatments was 12. In the soil depths 0-25 and 25-50cm the distribution of N and S was differed significant among the treatments. Let¬tuce yields were reduced significant (p<0.0001) when grown in intercropping with broccoli, whereas broccoli was less affected by cropping system. In addition, treat¬ments influenced both S and N uptake, and glucosinolate concentration.