Weed Management in Organic Conservation Tillage/No Tillage

Weed Management in Organic Conservation Tillage/No Tillage

Summary

We continued with successful field and laboratory experiments to develop organic no-till systems for soybean production.  Brassica and rye cover crops were planted in fall and soybeans drilled into standing cover crops, with appropriate no-cover crop controls. Weed control was excellent in rye plots, but brassica cover crops were not successful. Comparisons of small grain crops showed that rye was most effective, followed by wheat and spelt; barley and triticale were not effective. In laboratory studies, we found several seed extracts with significant suppression of weed seed germination, but no effect on photosynthesis or growth in postemergence applications.

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: We have completed the construction of the cover crop roller and tested it for two growing seasons on several cover crops. Our roller is simpler to construct than those described from elsewhere, but it could be improved by using 2-inch rather than 4-inch angle-iron for crimping the cover crops. However, comparison studies have shown that when weed populations are not high, the need for the roller is questionable, and simply drilling into standing rye is equally effective (one year’s data only).

Objective 2: In two years of field trials at two locations, only rye cover crops gave sufficient season-long weed suppression. We attempted to combine rye with brassica, but the optimum seeding dates for the two species differs greatly in our area, so we did not get a good stand of both species.

Objective 3: The field application test was not successful due to very dry conditions just after application. This study will be repeated if a no-cost extension is approved.

Objective 4: Some promising extracts have been found, from seeds of carrot and parsley, with variable activity from seeds of rye, buckwheat, mustards, and clovers. The appeal of this approach is that seeds of these species are available on the market and the quality is expected to be fairly consistent, as opposed to allelopathic chemicals that might be found in stems or roots.

Impacts and Contributions/Outcomes

Development of weed management practices using cover crops and plant extracts will make it possible for organic grain producers to use no-till production practices that reduce the negative impact of tillage on soil quality. One of the main criticisms of organic production, especially in areas with rolling topography, is the extensive use of tillage, which requires significant labor and fuel, and leaves the soil bare and susceptible to high rates of erosion.

Our system, if successful, will allow organic growers to reap the soil conserving benefits of no-till, at least in part of their crop rotation. The current experiments are with soybeans, but we are also working with a farmer who is trying this approach with corn. The potential application of these methods go beyond organic production and have attracted the interest of conventional growers, especially those who do not want to plant GMO soybeans: if the cover crops are effective, there is no need for glyphosate or other postemergence herbicides

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