Cover Crops and Conservation Tillage
for Soil Erosion Control on Cropland
Corn after forage - Rotations in Established Crownvetch
When rotating from hay back to corn, be careful not to eliminate the crownvetch, which has all but disappeared from view. In research trials at Penn State, crownvetch persisted through three years of alfalfa and alfalfa-grass mixtures, and was still present when the field was rotated back to corn. Whether crownvetch can survive four to five years in a hay stand is not known.
Since quackgrass usually invades hay stands in Pennsylvania, Roundup or Touchdown is recommended when rotating out of a forage to corn the first year (Table 4). If applied when dandelions are in full bloom, Roundup or Touchdown will not severely injure crownvetch, because crownvetch is just breaking dormancy at this time and has little foliage.
If dandelion is a major problem, a mixture of Lightning + Basis Gold on IR/Clearfield corn 3 weeks after the Roundup or Touchdown application is the best choice (Treatment 11, Table 4). Crownvetch will be very weak the first year and may appear to be killed completely, but in Penn State research trials it has always come back.