Cereal Cover Crops for Early Season Weed Control in Organic Field Beans.

Cover crops can be a successful weed control tool in integrated farming systems. In the Midwestern United States, there has been substantial research on the use of fall rye cover crops in soybeans. However, there are few studies in Manitoba on cover crops or their use in pulse production. Organic field beans in particular stand to benefit since they are very poor competitors.  This study compares three cereal cover crops, fall rye (Secale cereal L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.) to a no cover crop control for early season weed suppression in organic navy beans (Phaseolus vulgaris L.). Tillage and no-till management of the cover crops prior to seeding is also contrasted, where mowing at fall rye anthesis is used for no-till fall rye termination. The objectives are to compare weed suppression and the physical effects of cover crops and their management on several microclimate parameters. Preliminary results show that at pulse seeding, fall rye had reduced weed biomass (46 kg/ ha) compared to barley (117 kg/ha), oats (302 kg/ ha) and the control (329 kg/ ha). Mean light interception was highest in fall rye no-till plots (948 µmol s^-1 m^-1) 18 DAP. Also at pulse seeding, mean surface soil nitrate (0-15 cm) was lowest in fall rye plots (3.2 kg/ha). Plots that received tillage had higher soil nitrate (0-15 cm) 18 DAP and higher weed richness compared to no-till plots. Fall rye provided superior weed control, however early season competition for resources may have contributed to delayed pulse development. Tillage plots may have higher resource availability which is contributing to higher weed richness. Final results are pending the 2012 growing season.

Keywords: cover crops, organic, weed, field beans