Financial analysis of growing no till organic field corn and wheat using cover crops for weed suppression

Final Report for FS08-231

Project Type: Farmer/Rancher
Funds awarded in 2008: $8,827.00
Projected End Date: 12/31/2010
Region: Southern
State: Virginia
Principal Investigator:
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Project Information



Organic dairy farmers must feed organically grown corn and wheat to their dairy herds in order to sell organic milk. Due to the unavailability of organically grown corn and wheat, Virginia feed mills supplying organic feed to dairy producers must import organic corn and wheat from neighboring states. A feed mill in Lancaster, PA purchases organic wheat and corn from neighboring states and the Midwest because Pennsylvania is a grain deficient state. The wheat will be used as milling flour for human consumption. If the wheat does not meet the standards for milling wheat then the wheat is used in dairy feed.

The organic methods for corn production which rely on extensive tillage have been unsatisfactory. Organic and sustainable production of corn demands a lush cover crop. The incorporation of this cover crop in preparation for planting has been proven to be problematic

The field production of organic no till corn and wheat using cover crops has not been tested to a large degree in Virginia. Farmers do not have do not have information on the practicality of these production methods and the financial costs and returns of organic no till production of corn and wheat using cover crops.

Project Objectives:

We will establish side by side plots in Syria, Virginia to document the profitability and yields of growing organic corn in a no till system by comparing the effectiveness of using four cover crops for weed suppression.


Materials and methods:

The project was designed to test the suitability of four separate combinations of cover crops to control weeds in a corn crop without the use of herbicide. Two acre fields were seeded with: oats and crimson clover; oats and hairy vetch; rye and winter peas; and, rye and vetch. The spring oat variety was chosen to provide winter ground cover and then winter kill.

Disc blades on an offset disk were replaced with narrow wave coulters. The disk gang angle was eliminated. This was used to flatten and crush the cover crop and in the fall to slice crop and weed residue before planting wheat.

The minimum tillage used to prepare for cover crops failed to rid the fields of fescue. The most problematic field was turned over before seeding barley and barley/vetch, which was substituted for wheat in order to repeat growing a row crop (sunflowers) in rolled cover crops.

In this two year crop rotation, economic viability was not achieved, except for the hard winter wheat. Since this was primarily a no till experiment, it was decided not to intervene with a cultivator on two of three fields, in order to observe what the cover was actually capable of. The third field was cultivated once after a foxtail inundation. In all the planted fields, the cover allowed the corn to get ahead of weed competition. A greater difference in height between the corn and emerging weed pressure facilitates cultivation. There is a reasonable expectation that at least one cultivation can be consistently eliminated by planting into rolled cover.
Crimson clover was lightly rolled to test the concept of a living mulch. This produced a 50 to 75per cent kill. Certain areas within this field that had optimal clover growth gave the best indication of a successful less tillage system.

Rye cover was expected to give the best weed control. Deer pushed the rank growth down in all directions and made it impossible to plant through.

The impenetrable mat together with nitrogen tie up, makes rye a liability in a system for corn.

Winter killed oats and vetch provided the opposite planting conditions. Seed to soil contact was consistent and the soil moisture excellent. Fall planted winter wheat in this field yielded an estimated thirty-five bushels without additional added nutrients.
Sunflowers planted into rolled barley and vetch produced twenty-five per cent of the yield of cultivated sunflowers grown elsewhere on the farm.

In a repeat of these trials, the rye would be eliminated. The high residue cultivator would go in the field as soon as necessary.

Farming with this much ground cover, it is possible that field or contour strips would not be needed on sloping ground. Other questions that have arisen concern the technology hurdle. Seed placement through thick mulch is more about technology than agronomy.

Research results and discussion:

Farming with this much ground cover, it is possible that field or contour strips would not be needed on sloping ground. Other questions that have arisen concern the technology hurdle. Seed placement through thick mulch is more about technology than agronomy.

The trials have clarified some critical details. Just as cover crops must be crushed but not sliced to expose soil, the planter coulters must disturb as little soil as possible. The old eight wave coulters and trash movers that disturb soil are counter-productive as they help germinate weed seed. The general realism concerning near term expectation is that cultivation will be used. Even with the cost of cultivating, the benefits of tilth, nitrogen, organic matter increase, and a dust free planting medium gives significant advantage to this system.

Participation Summary

Project Outcomes

Project outcomes:

To avoid the cost of time, fuel, machinery, and dust of pre-plant tillage, four combinations of cover crops were planted to test the efficacy of planting without herbicide and relying on rolled ground cover to prevent weed growth. Yield results for corn were negligible. Wanting to observe the full capability of the mulch to control weeds, cultivation was withheld, a critical decision that prevented viable yields; but, a decision easily reversed in future crops.

It was observed that legumes provided the most favorable planting conditions, possibilities for cultivator intervention and nitrogen.
Rye cover ranged from problematic to impossible.
Wheat planted after field preparation with two gangs of narrow wave coulters, yielded adequately and provided a harvest window between maturity and late weed pressure.

If not hamstrung by a strict no till mind set, planting into legume cover crops avoids the time and cost of spring field preparation and eliminates at least one cultivation.


Potential Contributions

Without successful yields and the general failure of adequate weed control, formal plans for outreach seemed to miss the mark. I am most interested in making the hard lessons learned in this project available long term. I welcomed an on-line inquiry from an Illinois farmer and provided a preliminary appraisal of the cover crop trials. I am not looking for a grand stage to advertise an incomplete system, but searching for those who are desiring to construct a superior cropping system.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.