Effects of Water Stress On Red Clover Stand Survival and Uniformity When Over-Seeded to Winter Wheat.

Red clover (Trifolium pratense), when included in corn-soybean-winter wheat rotations as an inter-seeded cover crop to winter wheat, confers environmental and economic benefits: 1) increased yield and productivity of all crops in the rotation, 2) decreased soil erosion and increased wet aggregate stability, 3) increased soil organic matter, 4) reduced nitrate leaching into groundwater and 5) reduces synthetic nitrogen fertilizer requirements.  In spite of these benefits, red clover inclusion in crop rotation has declined, in large part, due to non-uniformity of red clover stands.  Causes of red clover non-uniformity have not been conclusively determined though the effects of many management practices have been investigated.  We hypothesized that precipitation pattern and variation in soil moisture may cause red clover stand non-uniformity since differences in the frequency and quantity of rainfall are likely responsible for the significant site-year effect found in previous studies. We investigated the relationship between clover development and low soil moisture imposed before, during and after wheat flowering. Clover biomass accumulation was measured before and after the onset of each water-stress treatment as well as at wheat harvest.  By conclusively demonstrating that red clover non-uniformity is due primarily to drought mechanisms, effective strategies for improving red clover stands, including breeding efforts and management strategies, could be identified.