Weed Management in Organic Conservation Tillage/No Tillage

Weed Management in Organic Conservation Tillage/No Tillage

Summary

Comparisons of small grain crops showed that rye was the most effective winter cover for weed suppression in spring-planted no-till soybeans. Rolled rye was more effective than mowed rye in suppressing weeds, but yields did not differ for soybeans planted directly into standing rye and those planted following rolling of rye. Optimum rolling time was later than expected: rye did not stay on the soil surface if rolled before grain fill began during the first or second week of June. Laboratory and greenhouse studies demonstrated that seed extracts can suppress weed seed germination, and that effects varied with extraction method.

Objectives/Performance Targets

1. Complete construction on an Ohio model cover crop roller to be used in field experiments.
2. Evaluate weed suppression by killed and rolled brassica, wheat, and rye cover crops for no-till soybeans.
3. Evaluate plant extracts and other natural products for weed suppression in the field.
4. Evaluate plant essential oils and extracts in preliminary screenings.

Accomplishments/Milestones

Objective 1: Construction and testing of the cover crop roller has been completed and we have used it for three growing seasons on several cover crops. The roller design was not optimal, but it has held up under minimal use for these experiments. The next design will use 4-inch angle-iron for crimping the cover crops, although published designs are likely more reliable.
Objective 2: Rye cover crops gave sufficient season-long weed suppression in no-till soybeans with no herbicide and no further cultivation. Standing rye suppressed spring-germinating weeds and took N away from N-loving weed species. It is possible that rye also suppressed weeds by allelopathy. Soybeans formed a quick canopy that shaded the few additional weeds that might have emerged after the relatively late planting date (June 10). The soybeans grew well in the low-N environment and fixed their own N. Even though the rye cover crop pulled water out of the soil, there was ample rainfall and adequate soil moisture for soybean growth.

Objective 3: The field application test was delayed to allow us to optimize the extraction process, which has been inconsistent. We were also concerned about safety issues regarding extracts that might have undesirable activity, such as skin irritation.

Objective 4: We continue to test extracts from readily available crop seeds, with activity demonstrated from carrot and parsley. None of the extracts have demonstrated postemergence activity in spite of one early test indicating possible positive effects from one species.

Impacts and Contributions/Outcomes

Several growers in our region are using no-till production practices in organic feed-grain soybeans using methods similar to those we have studied. At the recent conference of the Ohio Ecological Food and Farming Association (OEFFA) meeting there was an entire session devoted to these practices. Most farmers are using fall-planted rye as a cover crop and drilling soybeans into the rolled or standing or mowed rye the following spring. This use of no-till production practices within an organic rotation will help reduce the negative impact of tillage on soil quality that is often a concern with organic agriculture. The main issue for these growers remains how to integrate the fall planting of rye into the crop rotation. The most logical place for it is after harvest of wheat or possibly a summer forage crop. Since drawing down the soil nitrogen is thought to be helpful for weed control, the rye should not follow a clover crop.

Larger scale use of this system will allow organic growers to reap the soil conserving benefits of no-till, at least in part of their crop rotation. A farmer who tried this approach with corn reports questionable results, but there are many variables to manipulate to help make the corn system feasible. The use of the rye cover crop to replace herbicides in spring has attracted the interest of conventional growers, especially several who do not want to plant GMO soybeans.
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