Organic no-tillage system effects on soybean, corn and irrigated tomato production and economic performance in Iowa, USA

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Abstract
Novel technologies to reduce tillage in organic systems include a no-tillage roller/crimper for terminating cover crops prior to commercial crop planting. The objective of this experiment was to compare: (1) weed management and yield effects of organic tilled and no-tillage systems for corn (Zea mays L.), soybean [Glycine max (L.) Merr.] and irrigated tomato (Lycopersicon esculentum Mill.), using a roller/crimper and two cover crop combinations [hairy vetch/rye (Vicia villosa Roth/Secale cereale L.) and winter wheat/Austrian winter pea (Triticum vulgare L./Pisum sativum L. ssp. arvense (L.) Poir.)]; and (2) the economic performance of each system. Weed management ranged from fair to excellent in the organic no-tillage system for soybean and tomato crops, with the rye/hairy vetch mulch generally providing the most weed suppression. Corn suffered from low rainfall, competition from weeds and hairy vetch re-growth and, potentially, low soil nitrogen (N) from lack of supplemental fertilization and N immobilization during cover crop decomposition. No-tillage corn yields averaged 5618 and 634 kg ha−1 in 2006 and 2007, respectively, which was 42–92% lower than tilled corn. No-tillage soybeans in 2007 averaged 2793 kg ha−1 compared to 3170 kg ha−1 for tilled soybeans, although no-tillage yields were 48% of tilled yields in the dry year of 2006. Irrigated tomato yields averaged 40 t ha−1 in 2006 and 63 t ha−1 in 2007, with no statistical differences among tillage treatments. Economic analysis for the three crops revealed additional cover crop seed and management costs in the no-tillage system. Average organic corn returns to management were US$55,515 in the tilled system. Overall, the organic no-tillage soybean and irrigated tomato system demonstrated some promise for reducing tillage in organic systems, but until economic benefits from soil carbon enhancement can be included for no-tillage systems, soil improvements probably cannot offset the economic losses in no-tillage systems. Irrigation could improve the performance of the no-tillage system in dry years, especially if grain crops are rotated with a high-value irrigated tomato crop.