Weed Control in Organic Cropping Systems Using a Roll-Kill/No-till Technique with Cover Crops.

Weed Control in Organic Cropping Systems using a Roll-Kill/No-Till Technique with Cover Crops

Brinton, C. M., Reberg-Horton, S. C. and Grossman, J.

Advances in killing cover crops with a roller have opened up possibilities for organic farmers to reduce tillage.  This study examined multiple cover crop species and cultivars to determine which were suitable for use with a roller and their impact on subsequent cash crops.  Fourteen legume cultivars, across four species, were rolled and planted at two locations to examine the interaction between cover crop type and planting date.  Each cultivar was rolled and planted on 3 separate dates at each location.  For rye, six cultivars were rolled and planted on two dates at each location.  The appropriate roll date for the legumes varied from late-April to beyond the last planting in mid-May.  Less variation existed for rye, with approximately a two week gap amongst varieties in reaching the stage deemed appropriate for rolling (early milk).  At both locations, all rye cultivars were successfully roll-killed in mid-May; however, no legume was mature enough for rolling at typical corn planting dates.  The earliest successful roll date occurred on April 29^th for the crimson clovers and May 7^th for one cultivar of hairy vetch.  Vetches were the top biomass performers at the poorly drained Coastal Plain location but lagged behind crimson clovers in the Piedmont at the earliest planting date.  All rye cultivars can produce sufficient biomass to suppress weed growth (>9000 kg ha^-1); although, time requirements differ among cultivars and location.  In the Piedmont, most cultivars exceeded 9000 kg ha^-1 by the first roll date, May 21, 2009; and only increased 10% in the two weeks between roll dates.  A couple cultivars decreased in biomass over the same time, due to seed shed, resulting in volunteer rye in the following soybean crop.  In the Coastal Plain, two weeks between roll dates allowed northern cultivars to increase biomass by 30 – 45%.