Improving Alfalfa Stands with Early-Spring Broadcast Seeding

Abstract

A study was conducted to determine whether broadcast seeding of alfalfa (Medicago sativa L.) into a winter‐damaged alfalfa stand early in the spring would improve the stand and whether this seeding method could be a reliable alternative to conventional reseeding. In separate experiments conducted in 1986 and 1987 and followed for two growing seasons, alfalfa (‘Saranac’) seed was broadcast into winter‐damaged alfalfa plots, either as early in the spring as possible after the snow was gone (early April), or 2 wk later at the rate of 11 or 3.6 lb/acre. Stand improvement was evaluated on the basis of alfalfa density and dry matter yield. The effect of seeding date on density and yield was inconsistent and inconclusive. The recommended seeding rate of 11 lb/acre often resulted in better alfalfa populations and yields than the lower rate, although both seeding rates were generally better than leaving the plots unseeded. The effect of seeding rate on yield was only seen in the year following seeding. Success of reseeding was limited by poor germination, adverse effects of environmental conditions at seeding and later in the growing season, and possibly, by auto‐allelopathy. While there was some stand improvement, neither plant density nor yield was comparable to a vigorous alfalfa stand. The maximum density obtained was 6 plants/sq ft, but this was not maintained. Maximum total yield was only 2.83 tons/acre for three cuts. The results suggest that early‐spring broadcast seeding is not a good alternative to conventional reseeding on a large scale. It would, however, be suitable for repairing small areas of damage such as found in low spots in a field.

Alfalfa Autotoxicity

“…ha −1 on 15 October. A similar approach to simulate winterkill was used by Asbil and Coulman (1992) Because night air temperatures after application were frequently <0°C, it is unlikely that this treatment resulted in immediate kill of alfalfa. Treated plants likely stopped normal physiological processes within 7 to 10 d after herbicide treatment and altered winterhardiness.…”