Mob grazing is an effective method of sod suppression for graziers who don’t want to use chemicals before interseeding annual forages into perennial pastures for late-summer grazing. But glyphosate works better, say University of Minnesota researchers.

Two-acre paddocks dominated by Kentucky bluegrass, quackgrass and reed canarygrass were grazed by 30 cow-calf pairs for five days prior to seeding. Other paddocks were sprayed with 1 pint/acre of glyphosate. Then 25 lbs/acre of a mixture of 80% annual ryegrass and 20% Purple Top turnips was seeded with a no-till drill.

On day 17 after seeding, the interseeded crops covered only 12% and 14% of the ground in grazed and sprayed paddocks, respectively. Grazed paddocks were dominated by perennial grass regrowth and broadleaf weeds. Sprayed paddocks also had significant grass regrowth but few weeds.

By day 52, ryegrass and turnips covered 65% of grazed paddocks and 75.5% of those treated with glyphosate. Perennial grasses accounted for 15-20% of the ground cover in both treatments. Forage yield was 40% greater in sprayed paddocks than in grazed ones, the researchers report.