DIBOA and BOA production by eight rye cultivars and allelopathic effect of the mulch on four warm season weeds

In conventional agriculture weed control by herbicides is an expensive practice and can also have a negative effect on the environment. Allelopathy pennits sustainable weed management while reducing the impact of agriculture on the environment. We studied the content of 2,4-dihydroxy-l,4(2H)-benzoxazin-3-one (DIBOA) and benzoxazoUn-2(3H)one (BOA), indicated as benzoxazinoids and considered effective for weed control, in 8 cultivars of rye grown in a greenhouse, and also tested the ability of mulches to inhibit the gemination of four warm-season weeds. Our results show that all rye cultivars produced DIBOA, while BOA was found only in four of them. Total benzoxazinoid content ranged from 177 to 545 ~g 1 g-l and was statistically different among cultivars. Rye mulches were not able to suppress velvetleaf and common lambsquarters seedlings, while redroot pigweed and common purslane were significantly affected. Weed suppression ranged from 40 to 52% for redroot pigweed and from 40 to 14% for common purslane. No correlation was found between total benzoxazinoid content and the number of weed seedlings suppressed, with R' = 0.076 for redroot pigweed and R' = 0.003 for common purslane, indicating that benzoxazinoids are not the only source of phytotoxicity.