MANAGEMENT OF COVER CROPS FOR ENHANCEMENT OF HIGH VALUE CROPPING SYSTEMS
Title: POTENTIAL LONG-TERM BENEFITS OF SELECTED NO-TILLAGE AND ORGANIC CROPPING SYSTEMS FOR GRAIN PRODUCTION AND SOIL IMPROVEMENT
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 21, 2007
Publication Date: September 10, 2007
Citation: Teasdale, J.R., Coffman, C.B., Mangum, R.A. 2007. Potential long-term benefits of selected no-tillage and organic cropping systems for grain production and soil improvement. Agronomy Journal. 99:1297-1305.
Interpretive Summary: Crop production without tillage is well-known for increasing soil organic carbon which results in many other improvements in soil structure, water-holding capacity, and nutrient availability. Organic farming is also known to increase soil carbon and improve soils in many of the same ways as no-tillage production. However, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A nine-year comparison of selected minimum-tillage strategies for grain production of corn, soybean, and wheat was conducted on a sloping, droughty site in Beltsville, Maryland, from 1994 to 2002. After nine years, corn yields were 28% lower in the organic farming system than in the standard no-tillage system. Despite the use of tillage, soil carbon and nitrogen concentration were higher in the organic system compared to those in all other systems. A uniformity trial was conducted from 2003 to 2005 with no-tillage corn grown on all plots. Yield of corn grown on plots with a nine-year history of organic management were 18% higher than those with a history of conventional no-tillage production, probably as a result of higher soil carbon and nitrogen. These results suggest that organic farming systems can provide greater long-term soil improvement than conventional no-tillage systems, despite the use of tillage in organic systems. However, these benefits may not be realized because of difficulty controlling weeds in organic systems. Results can be used by advocates in the conventional-organic farming debate as well as by researchers, extension personnel, and growers who need guidance on selection of sustainable cropping systems.
There have been few comparisons of the performance of no-tillage cropping systems versus organic farming systems, particularly on erodible, droughty soils where reduced-tillage systems are recommended. In particular, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A nine-year comparison of selected minimum-tillage strategies for grain production of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) was conducted on a sloping, droughty site in Beltsville, Maryland, from 1994 to 2002. Four systems were compared: 1) a standard Mid-Atlantic no-tillage system (NT) with recommended herbicide and nitrogen inputs, 2) a cover crop-based no-tillage system (CC) including hairy vetch (Vicia villosa Roth) before corn and rye (Secale cereale L.) before soybean with reduced herbicide and nitrogen inputs, 3) a no-tillage crownvetch (Coronilla varia L.) living mulch system (CV) with recommended herbicide and nitrogen inputs, and 4) a chisel-plow based organic system (OR) with cover crops and manure for nutrients and post-planting cultivation for weed control. After nine years, competition with corn by weeds in OR and by the crownvetch living mulch in CV was unacceptable, particularly in dry years. On average, corn yields were 28 and 12% lower in OR and CV, respectively, than in the standard NT whereas corn yields in CC and NT were similar. Despite the use of tillage, soil combustible C and N concentration was higher at all depth intervals to 30 cm in OR compared to that in all other systems. A uniformity trial was conducted from 2003 to 2005 with NT corn grown on all plots. Yield of corn grown on plots with a nine-year history of OR and CV were 18 and 19% higher, respectively, than those with a history of NT whereas there was no difference between corn yield of plots with a history of NT and CC. Three tests of nitrogen availability (corn yield loss in subplots with no nitrogen applied in 2003-2005, pre-sidedress N test, and corn ear leaf N) all suggested that there was more N available to corn in OR and CV than in NT. These results suggest that OR can provide greater long-term soil benefits than conventional NT, despite the use of tillage in OR. However, these benefits may not be realized because of difficulty controlling weeds in OR.