Yield Response to Cultivation of Established Alfalfa

As alfalfa (Medicago saliva L.) stands deteriorate, weeds compete with alfalfa and further reduce yield. Some growers in the northern Great Plains attempt to renovate alfalfa with intensive cultivation during spring. Implements used include tandem disks, chisel plows, and various harrows. Some implement manufacturers market specialized attachments intended for cultivation of alfalfa. Common rationale for cultivation includes weed control, soil nutrient incorporation, repair of compacted soils, and smoothing mounds caused by rodents. Agronomists have received many questions concerning the cultivation of alfalfa fields. Therefore, research was initiated near Rapid City in the fall of 1993, and near Rapid City and Waverly in the fall of 1994 to determine the effects of cultivation on weed control and components of alfalfa. Spring cultivation was done with a spike-tooth harrow, spring-tooth harrow, tandem disk, and a Triple K harrow. Herbicides included Pursuit and Sencor applied during autumn to dormant alfalfa. Cultivation treatments were conducted when alfalfa was breaking dormancy. Subsamples from each treatment were hand separated to determine composition of alfalfa, grasses and broadleaf weeds. Although the disk and Triple-K disturbed the soil extensively, forage yield was not affected. Inconsistent control of grass weeds was observed and none of the alfalfa yield components were significantly altered by cultivation. Alfalfa shoot dry weight increased by 36% for one of the locations following cultivation. Harvests taken one year after cultivation showed no residual effects. These results suggest that attempting to renovate alfalfa stands with cultivation practices does not increase yield, control weeds, or increase plant density