Niche separation and nitrogen transfer in Brassica-legume intercrops

Abstract

Brassica sp. are interesting late-summer and autumn forages. Since they have high nitrogen requirements, intercropping with legumes may increase yield in low-input systems. However, brassicalegume intercrops still remain poorly documented. Using rhizotrons in a greenhouse, we compared root development of (1) forage rapeseed grown with faba bean to that of forage rapeseed monoculture and (2) fodder cabbage grown with common vetch to that of fodder cabbage monoculture. Legumes were labelled with 15N urea. Seven to eight weeks after sowing, Brassica yield and N content were higher under intercropping than in pure stand. Under intercropping, distribution of root ramifications along the taproot differed from that of monoculture, which reduced the effect of competition. In addition, N transfer from legumes to Brassica was found to be significant.

Keywords

• facilitation
• intercropping
• N fixation
• niche