This project examined whether targeted mowing of winter rye cover crop (Secale cereale L.) would increase its weed suppression ability by increasing levels of rye’s major allelochemicals, Hydroaxamic acids (Hx), and subsequently increase crop yield in an organic tomato production system. The project was conducted on organic farms in Upper Marlboro (2003), and Beltsville (2004), Maryland, using a rye cover crop that was grown as a monoculture and as a mixture with crimson clover, and black mulch.