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Title: High-residue cultivation timing impact on organic no-till soybean weed management

item ZINATI, GLADIS - Rodale Institute
item Mirsky, Steven
item SEIDEL, RITA - Rodale Institute
item GRANTHAM, ALISON - Rodale Institute
item MOYER, JEFF - Rodale Institute
item ACKROYD, VICTORIA - North Carolina State University

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 3/1/2017
Citation: Zinati, G., Mirsky, S.B., Seidel, R., Grantham, A., Moyer, J., Ackroyd, V. 2017. High-residue cultivation timing impact on organic no-till soybean weed management. Weed Technology. 31:320-329.

Interpretive Summary: Currently there are organic grain shortages for the meat and egg industry in the US. To meet the demand on organic grain, we will need both a scaling up of acreage from existing producers and transition to organic from conventional producers. The intensive tillage requirements of organic grain production limits both the scale for existing producers and limit adoption by soil conservation minded farmers. A successful reduced tillage organic grain production system is needed to reduce labor requirements for existing organic producers and attract more soil conservation minded conventional producers to organic grain production. Weed control is the primary limiting factor in the success of a reduced tillage organic grain production system. While cover crops are an important component of weed control, they do not typically provide season long control. Therefore, supplemental weed control tools like high residue cultivators are needed to limit weed competition. However, the optimal timing of these cultivators have not been determined. We designed an experiment at The Rodale Institute, PA to determine the optimal timing of high residue cultivation in organic soybean production. The study included three cultivation timings (early, intermediate, and late), no cultivation, and a weed-free control. We observed that the intermediate timing, 5-6 weeks after soybean planting, was the optimal timing for ensuring both good weed control and minimal impact on soybean yield. This work will be useful to organic producers and help them make decisions on weed control in cover crop-based organic rotational no-till grain production.

Technical Abstract: A cereal rye cover crop mulch can suppress summer annual weeds early in the soybean growing season. However, a multi-tactic weed management approach is required when annual weed seedbanks are large or perennial weeds are present. In such situations, the weed suppression from a cereal rye mulch can be supplemented with the use of high-residue cultivators which can prolong the weed-free period during soybean growth. Research trials were conducted to determine the optimum timing of high residue cultivation for weed control in rolled-crimped cereal rye mulches. Treatments included three cultivation timings with a high-residue cultivator: early (3-4 wk after soybean planting (WAP)), intermediate (5-6 WAP), and late (7-8 WAP), a weed-free and no-cultivation control. Crop and weed measurement included cereal rye biomass, weed biomass, soybean population and biomass, and yield. Cereal rye biomass was 50% lower and weed biomass was three times greater in 2011 than in 2010 and 2012 due to 2011 being a dry year. There was no significant effect of cultivation timing on soybean population when compared to no-cultivation or handweeded treatments. While cultivation reduced weed biomass by 67% compared to nocultivation, soybean yield was only improved by 12% in early and late cultivation treatments and 22% in intermediate cultivation treatment when compared to nocultivation. Effective strategies for improving weed management by integrating the use of a high-residue cultivator in no-till organic systems could help existing organic field crop producers to reduce tillage while also encourage adoption of organic crop production by conventional growers who prefer reduced-tillage systems. High-residue cultivators more efficiently terminate larger weeds than smaller weeds, unlike traditional organic cultivation equipment, therefore, optimal timing of cultivation should be delayed several weeks in organic cover crop-based no-till planted corn production as compared to the typical tillage based approach to ensure both weed control and optimal yield.