No-Till Alfalfa Planting in Late Winter Following Fall Vegetation Suppression with Herbicides

Successful establishment of no-till alfalfa (Medicago sativa L.) in spring and late summer is limited by soil moisture, weed competition, and disease. Thistudy tested an alternative planting time that partially avoids these problems. Vegetation was suppressed with fall-applied herbicides and plantings were made in late winter (early March). Plantings were made into Typic Hapludult and Typic Fragiudult soils. All areas received 2,4-D [(2,4-dichlorophenoxy) acetic acid] in late August, but this could have been omitted if no broadleaf weeds had been present. A no-herbicide treatment was included as a check. Herbicide suppression included glyphosate [N-(phosphonomethyl) glycine] at 3.4 kg ha⁻¹ on 1 October, paraquat (1, l′-Dimetyl-4, 4′-bipyridinium ion) applied once on 1 October or 1 November at 0.56 kg ha⁻¹, or a split paraquat application with 0.56 kg ha⁻¹ applied 1 October and 0.28 kg ha⁻¹ applied 15 November. Treatments were harvested three times in the year of establishment and four times in the year after seeding. Excellent seedling emergence occurred from all treatments in each year, so yield differences were due to success of weed suppression by herbicides. No-till alfalfa planted in early March resulted in vigorous seedlings where original species in the sod were suppressed the previous fall. Vigor and productivity of plants established without herbicide was not satisfactory. Percentage alfalfa in the harvested herbage and yields in both harvest years tended to be higher for the split application of paraquathan other treatments even though this was not always significant (P ≤ 0.05). The split paraquat treatment was more consistent between sites and years than the glyphosate or single paraquat treatments. These results suggest that in environments similar to the test site (37 ° N, 80 ° W, and 600-m elevation) high yielding alfalfa stands can be established using fall applications of a split paraquat treatment, followed by late-winter planting with a no-till drill. Contribution from the Dep. of Agronomy, Virginia Polytechnic Inst. and State Univ.