Organic No-till in Iowa: Many Challenges to Overcome.

Organic production in the U.S. increased to 4.1 million acres in 2005, with 252,889 acres of organic corn (Zea mays L.) and soybean [Glycine max (L.) Merr.], and 98,525 acres in organic vegetable crops. This increase has been attributed to the application of consistent federal standards since 2002 for products marketed as organic, and a growing consumer preference for lower pesticide residues in food. One of the criticisms of organic farming has been the requirement for multiple tillage passes for weed management over the field season. In 2006 and 2007, a certified organic site at the Iowa State University Neely-Kinyon Farm in Greenfield, Iowa, was selected for an experiment on organic no-till production. Plots were laid out in a randomized complete block design of three treatments with three replications. The treatments: 1) a control, with tillage used before and after commercial crop planting (tilled treatment); 2) no-till cover crop combination of winter wheat and Austrian winter pea; and 3) no-till cover crop combination of rye and hairy vetch were established in the fall preceding spring corn and soybean planting.  In 2006, corn plant populations in the wheat/winter pea no-till treatment, averaging 20,833 plants/acre, were lower than the tilled treatment, but the tilled and rye/hairy vetch no-till treatments were equivalent, averaging 24,667 plants/acre. Plant height also was affected by the combination of drought and cover crop competition, as corn plant height was reduced in both cover crop no-till treatments compared to the tilled treatment. Corn yield was reduced in the no-till treatments, averaging 90 bu/acre across both cover crop treatments, compared to 155 bu/acre in the tilled treatment. In 2007, June rainfall was reduced by 1.6 inches, with 2.2 inches below normal in July. Corn plants in the no-till treatments suffered from the dry weather more than soybeans in 2007. Plant stands were similar between tilled and no-till treatments, averaging 20,139 plants/acre, but growth was depressed as the season progressed and water became a major limiting factor in July. In 2007, corn yields in no-till plots averaged only 10 bu/acre, compared to 125 bu/acre in tilled plots. Soybean plant populations in 2006 were affected by rotary-hoeing operations in the tilled treatment, which had lower plant populations than both no-till cover crop treatments, which averaged 88,250 plants/acre. Soybean yield in 2006 in the no-till treatments in 2006 averaged 17 bu/acre across both cover crop treatments, compared to 35 bu/acre in the tilled treatment. Organic no-till soybean yields were excellent in 2007, however, averaging 45 bu/acre across both cover crop treatments. Yields in tilled plots were greater than no-till plots, at 51 bu/acre. These results suggest that organic no-till offers potential for organic soybean production, particularly when rainfall is adequate during the season.