Author
 |
Forcella, Frank |
|
Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/6/2012 Publication Date: 1/27/2013 Citation: Forcella, F. 2013. Short- and full-season soybean in stale seedbeds versus rolled-crimped winter rye mulch. Renewable Agriculture and Food Systems. 29(1):92-99. Interpretive Summary: Late seedbed preparations (also known as stale or false seedbeds) are used by organic growers to reduce weed populations prior to crop planting. Rye mulches, derived from mechanically killed (rolled and crimped) winter rye cover crops, can serve the same purpose for spring-planted organic crops. Both methods also can be employed by conventional growers who face looming problems with herbicide resistant weeds. These methods were compared over two years in central Minnesota in terms of weed seedling emergence, populations, biomass, and hand-weeding (hand-hoeing + hand-pulling) times, as well as stands and yields of short- season and full-season soybean varieties planted late, in mid June. Rye mulch greatly lowered both pre- and post-planting weed populations of common annual weeds, which substantially affected necessity for augmented weed control. For instance, the need for within-crop hand-weeding was low for soybean planted into rye mulch (0 to 2 hours per acre), but ranged from 6 to 26 hours per acre of labor for soybean planted in stale seedbeds (with weed control augmented by pre-emergence herbicide and inter-row cultivation). However, rye mulch lowered soybean yield potential by 800 to 1000 lbs per acre compared to stale seedbeds. With organic feed-grade soybean seed valued at $0.45 per pound, conventional soybean seed at $0.22 per pound, and labor for hand-weeding at $10 per hour, the use of rye mulch compared to stale seedbeds augmented by hand-weeding are equally rational choices for organic growers in central Minnesota (assuming labor is available for hand-weeding), but rye mulches probably would be a wise financial option for conventional growers. Lastly, full-season soybean had higher yields than short-season soybean and likely represents a prudent selection in central Minnesota, regardless of the late planting date requirements for both the rye mulch and stale seedbed systems. Technical Abstract: Late seedbed preparations (also known as stale or false seedbeds) are used by organic growers to reduce weed populations prior to crop planting. Rye mulches, derived from mechanically killed (rolled and crimped) winter rye cover crops, can serve the same purpose for spring-planted organic crops. Both methods also can be employed by conventional growers who face looming problems with herbicide resistant weeds. These methods were compared over two years in central Minnesota in terms of weed seedling emergence, populations, biomass, and hand-weeding (hand-hoeing + hand-pulling) times, as well as stands and yields of short- season and full-season soybean varieties planted late, in mid June. Rye mulch greatly lowered both pre- and post-planting weed populations of common annual weeds, which substantially affected necessity for augmented weed control. For instance, the need for within-crop hand-weeding was low for soybean planted into rye mulch (0 to 6 h ha-1), but ranged from 15 to 66 h ha-1 of labor for soybean planted in stale seedbeds (with weed control augmented by pre-emergence herbicide and inter-row cultivation). However, rye mulch lowered soybean yield potential by 800 to 1000 kg ha-1 compared to stale seedbeds. With organic feed-grade soybean seed valued at $1 kg-1, conventional soybean seed at $0.5 kg-1, and labor for hand-weeding at $10 h-1, the use of rye mulch compared to stale seedbeds augmented by hand-weeding are equally rational choices for organic growers in central Minnesota (assuming labor is available for hand-weeding), but rye mulches probably would be a wise financial option for conventional growers. Lastly, full-season soybean had higher yields than short-season soybean and likely represents a prudent selection in central Minnesota, regardless of the late planting date requirements for both the rye mulch and stale seedbed systems. |
