Slurry seeding a legume into grass pastures can increase forage yield and quality and provide a more complete feed for grazing livestock, says Tim Harrigan, Michigan State University ag engineer.

He used the method to seed 10 lbs/acre of red clover into smooth bromegrass sod and compared the resulting pasture yields to those achieved with no-till drilling and frost seeding. The slurry seeding was done with 4,000 gallons/acre of liquid swine manure, which supplied 70 lbs/acre of total nitrogen.

All three methods improved pasture yields compared with untreated control plots. Total forage dry matter yield for the first two growing seasons was 11.2 tons/acre for no-till drilling, 10.3 tons/acre for slurry seeding and 7.9 tons/acre for frost seeding.

Slurry seeding pastures is challenging, Harrigan warns, because manure stimulates growth of existing grasses.

“You try to strike a balance between using manure nutrients to create a nutrient-rich environment for the seed, but on the other hand you don’t want to stimulate it so much that the existing forage really takes off and outcompetes the new seedlings.”

He recommends applying less than 100 lbs/acre of nitrogen in the manure. In Michigan, the seeding should be done in mid- to late August, preceded by a close grazing.

“Then we like to see them keep the cattle off that for the rest of the fall,” he says.