Summer and Winter Cover Crops Are Effective Tools for Weed Management in Organic Production Systems.

Organic farming, an environmentally-friendly alternative to conventional chemical-based agriculture is perhaps the fastest growing sector in Agriculture. Weeds are a major factor limiting expansion of organic production worldwide. Cover crops can be an economically viable tool for controlling weeds in addition to their multiple benefits to soil and crop productivity. In two separate field experiments, five species each of summer (Sudan x Sorghum Hybrid, sunflower, velvet beans, buckwheat, and iron-clay peas) and winter cover crops crimson clover, hairy vetch, rye, canola, and Austrian winter peas) were compared to no-cover crop control for their biomass and weed control.  All cover crops reduced weeds in both seasons, but the relative efficiency of weed suppression varied significantly with cover crop species.  Among summer cover crops, iron-clay peas, Sudan x sorghum hybrid and sunflower with high biomass (4.8 – 6.3 Mg ha^-1) significantly reduced  weeds (weed biomass of 0.9 to 1.3 Mg ha^-1) compared to  Control (weed biomass of 3.5 Mg ha^-1).  Among winter cover crops, rye with 6.5 Mg ha^-1 of biomass was the best in suppressing weeds (weed biomass of 0.3 Mg ha^-1) followed by crimson clover (crop biomass of 5.6 Mg ha^-1 and weed biomass=0.8 Mg ha^-1).  Hairy vetch had very poor stand and was dominated by weeds but the weed biomass was significantly less that in Control.  Weed suppression by cover crop was significantly correlated with cover crop canopy, biomass, and light interception. The study showed the potential of cover crops for effective weed management provided cover crop has good establishment.