Development of winter cover crop varieties and complementary mixtures for North Central Region grain systems

Development of winter cover crop varieties and complementary mixtures for North Central Region grain systems

Summary

Field evaluations of hairy vetch as a winter cover crop in row crop ecosystems concluded that varieties varied in morphology and phenology, and produced different amounts of biomass, but the difference between varieties did not influence final corn crop biomass.

Mixtures of hairy vetch varieties were either beneficial or detrimental depending on the specific varieties in the mixture.

Preliminary data suggest that common hairy vetch (Oregon origin) is the best adapted variety for October seeding in SW Michigan. Comparative studies in 2008 will help to clarify the best adapted hairy vetch varieties for summer and fall planting in Michigan and Nebraska.

Objectives/Performance Targets

Short Term Outcomes
1. Hairy vetch varieties identified and characterized for MI and NE grain producers,
2. Evaluation of genetic diversity within a cover crop species,
3. Knowledge disseminated to farmers about the benefits and drawbacks of diversified cover crop mixtures.

Intermediate Term Outcomes
4. Cover crop-mediated nitrogen cycles for reduced leaching and external inputs,
5. Climactically and environmentally buffered cover crops in non-irrigated fields,
6. Sustainable options for farmers as they face rising external fertilizer prices.

Accomplishments/Milestones

1. Optimal hairy vetch and red clover varieties identified and characterized for MI and NE grain producers

In controlled environment conditions, three hairy vetch varieties (Common – Oregon origin, Nebraska origin and ‘AU Early Cover’) survived freezing temperatures of -6 oC. Common hairy vetch has few leaf hairs, grows quickly, and is sold throughout the U.S. under the “variety not stated” (VNS) label, and is primarily produced on seed farms in the U.S. Pacific Northwest. Nebraska hairy vetch is large seeded, slow growing, very pubescent, and appears to be related to what was once known as the ‘Madison’ hairy vetch cultivar. ‘AU Early Cover’ is an early flowering variety, and grows for a shorter period of time than other varieties.

When seeded in October, 2006, Common hairy vetch produced more biomass (114 g / m2) than Nebraska (78 g / m2) and ‘AU Early Cover’ (86 g / m2) by May 19, 2007. Nebraska hairy vetch produces larger seeds than the other two varieties, which resulted in the need to seed this variety at a higher rate than the other two varieties to maintain similar plant density, resulting in higher seed costs. On average, varieties supplied 36% of the nitrogen needed for subsequent corn crop growth in 2007, which was a drought year. In non-drought years, we estimate that October seeded hairy vetch would supply less than 36% of the needed nitrogen for corn growth due to higher demands by the corn crop.

On farm trials in Nebraska determined that October seeding of cereal rye / Nebraska hairy vetch mixtures reduced subsequent corn crop growth, likely due to soil water depletion and nitrogen immobilization by the cereal rye. However, August seeded vetch / rye mixtures produced valuable fodder for winter cattle grazing, but vetch growth the following spring was qualitatively deemed inadequate by the farmer to reduce inorganic nitrogen fertilizer rates. Two red clover varieties (Canada Mammoth VNS and ‘Starfire) exhibited poor establishment when frost seeded in March in a dry-land wheat field.

In 2008, we are continuing to evaluate October seeded hairy vetch varieties for biomass production and benefits to subsequent corn crops. In addition, we are evaluating August plantings of the same and additional hairy vetch varieties to simulate the cover crop seeding window after small grain harvest. In the same field, for a six March frost seeded planting date, red clover varieties and alfalfa are being compared to the hairy vetch varieties seeded in August. In 2008, Farmers in Nebraska and SW Michigan plan to evaluate two August seeded hairy vetch varieties and two March, 2007 frost seeded red clover varieties.

2. Evaluation of maintaining genetic diversity within a cover crop species

Combining hairy vetch varieties did not produce consistent results. The mixture of Common and ‘AU Early Cover’ overyielded compared to respective monocultures and produced 85% of the nitrogen needed for corn growth. Contrarily, the mixture of Nebraska and ‘AU Early Cover’ underyielded compared to respective monocultures, and reduced corn crop growth below that of no-cover control plots.

In 2008, we are evaluating the same hairy vetch mixtures seeded in August and October of 2007, and are evaluating two red clover variety mixtures for biomass production and nitrogen supply. A farmer in Nebraska planted a mixture of Nebraska and Common hairy vetch to evaluate the performance of the mixture compared to monocultures of each variety.

3. Knowledge disseminated to farmers about the benefits and drawbacks of diversified cover crop mixtures

Michigan farmers and extension agents visited field trials at the W. K. Kellogg Biological Station (KBS) in September, 2007, and initial discussions started. Some limited data presented, further data will be analyzed and disseminated in 2008 . Subsequent field days held at KBS in 2008 and 2009, will be an opportunity for area farmers to be invited to visit on farm trials in Michigan and Nebraska. A final report will be written for dissemination through the New Agriculture Network, and a one page handout will be distributed to interested farmers in Nebraska and Michigan.

4. Tighter nitrogen cycles (reduced leaching and external inputs)

Two long term experiments in agroecology at KBS have collected data on nitrogen inputs and exports for 19 years and 15 years respectively. Data from these two experiments shows that red clover cover crops can be used to reduce nitrogen fertilizer rates by 67% while maintaining equal or higher grain yields. Yet, these low-input fields have similar levels of nitrate leaching compared to fully fertilized fields. Fields managed with only red clover cover crops and no inorganic fertilizer have lower nitrate leaching losses than those managed with inorganic fertilizer, but comes at a tradeoff of lower grain yields. We are conducting a complete analysis of nitrogen use efficiency in fields using inorganic fertilizer versus those that relied specifically on legume cover crops as a nitrogen source.

5. Climactically and environmentally buffered cover crops in non-irrigated fields

Mixtures of hairy vetch varieties produced mixed results in terms of biomass, but the variability in biomass production across research plots was lower than the variability across monoculture plots. This result indicates that variety mixtures may help to provide more stable cover crop production in variable climates, soil conditions and when knowledge about cover crop performance is unknown. We have also identified three hairy vetch varieties that survive winter conditions in Southwest Michigan (Common, Nebraska and ‘AU Early Cover’). When seeded in October, 2006, these three varieties did not deplete soil moisture more than the no-cover crop control plots.

We will continue to evaluate the variability in biomass production of variety mixtures and monocultures in 2008.

6. Sustainable options for farmers as they face rising external fertilizer prices

October hairy vetch planting, which is a realistic time for corn-soybean farmers, provided only 36% of the nitrogen needed by subsequent corn crops in a drought year. Hairy vetch seed can range from $25 – $50 per acre, which makes it currently uneconomical to use hairy vetch as an October seeded cover crop. We will continue to evaluate the economical value of using hairy vetch and red clover varieties, for both August and October plantings.

Impacts and Contributions/Outcomes

• Through experimenting with hairy vetch / rye cover crops, a Nebraska farmer discovered that August seeded cereal rye provided substantial amounts of feed for cattle via grazing in the winter. Three hairy vetch varieties were identified as winter hardy in the North Central Region, including ‘AU Early Cover,’ which flowers earlier in the spring than other varieties and may be easily killed using organic no-till management. October hairy vetch plantings reduced nitrogen fertilizer needs by an average of 36% during a drought year. Mixing hairy vetch varieties reduced variability in cover crop growth, and one mixture outyielded the respective hairy vetch monocultures. Now that we have characterized several hairy vetch varieties in the greenhouse and field, farmers have information to help match hairy vetch varieties to specific functions in crop fields, such as early flowering and low soil water depletion. By the end of this project, farmers will have more information about variety-specific traits in hairy vetch cover crops and be able to estimate how much nitrogen they will obtain by planting different varieties over two planting windows.

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