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Introduction
Common ragweed (Ambrosia artemisiifolia L.) is an annual weed problem following winter wheat in southwest Michigan. Producers often use herbicides for spring weed control in winter wheat. A more sustainable weed control practice would incorporate red clover (Trifolium pratense L.) into winter wheat. Red clover can be frost-seeded into winter wheat with little to no impact on wheat yields, while harboring such beneficial insects as the lady beetle. Red clover consistently provides a stand of 140 or more plants/square meter and produces about 2240 kg/hectare of biomass by the following May. Plow-down nitrogen yields range from 100-200 kg/hectare, which can supply the equivalent of 90-112 kg N/hectare (fertilizer replacement value) for a subsequent corn crop. Most wheat herbicides kill red clover, so the cover crops program at the Michigan State University W.K. Kellogg Biological Station (MSU/KBS) has initiated a study to evaluate how red clover seeding rates and varieties influence weed suppression.
Objectives
- Compare c. ragweed suppression by three red clover cultivars frost seeded into winter wheat
- Evaluate each red clover cultivar at 6, 9 and 12 lbs/A for c. ragweed suppression
- Evaluate post wheat harvest biomass of c. ragweed and red clover as influenced by mowing vs. not mowing
Materials And Methods
- Wheat Planted: Oct. 15, 1997
- Fertilized N-50 lbs/acre actual: March 13, 1998
- Frost-seeded with Gandy air seeder: March 16, 1998
- Plot size: 10 X 120 feet
- Wheat harvested and yields taken: July 10, 1998
- Mowed ten feet wide strips with rotary mower to height of 6-8 inches: July 28, 1998
- Biomass of c. ragweed and red clover taken: Sept. 18 and 22
- Four square feet samples were clipped to ground level in each plot
- Red clover and c. ragweed were separated and placed in paper bag, dried and weighed
Results
- C. ragweed biomass was reduced when red clover was frost-seeded into winter wheat (chart 1)
- Each frost-seeding rate (6.6, 10, and 13.3 kg/ha) suppressed c. ragweed biomass similarly (chart 1)
- Each red clover cultivar in suppressed c. ragweed biomass similarly (chart 2)
- Post-harvest mowing reduced c. ragweed biomass in all treatments, however, larger differences were measured at all seeding rates of red clover (chart 3)
- Mowing reduced c. ragweed biomass, and increased red clover biomass (chart 4)
- KBS/MSU experienced drought conditions in July and August 1998.
- This experiment was repeated in 1999. Though red clover lowered c. ragweed biomass, farmers may not find these levels acceptable.
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