Research Summary: Improving Pasture and Hay-ground with Low-disturbance, Manure Slurry-enriched Seeding

Research Purpose

Many dairy producers in the Great Lakes Region have abandoned year-around confinement feeding and have adopted a form of managed grazing where cattle are on pasture during the growing season and housed during the winter months. Pasture land is often nutrient deficient because crop nutrients are removed in harvested hay early in the growing season when forage supply exceeds grazing demand. Thinning stands are often a problem on a grazing farm, particularly after a dry summer when over-grazing occurs.

The objective of this work was to develop and evaluate a process whereby forage Brassica, grass and legume seed was carried in nutrient rich manure slurry to seeding micro-sites in small grain stubble or established pasture and hay ground. This shallow mixing of the seed-laden slurry increased the species richness, yield and quality of hay and grassland, extended the grazing season, and provided a more complete, balanced feed for grazing stock.


Slurry seeding was done with a commercially available slurry tanker (3000 gal) equipped with a rear-mounted rolling-tine aerator (Aer-Way) and a SSD (sub-surface deposition) slurry distribution system. The rolling-tine aerator was ground-driven with 8-inch tines on a rotating shaft with 7½ inch spacing between each set of tines. The angle of the rotating shaft was adjustable in 2.5º increments from 0º to 10º degrees relative to the direction of travel. The 0º gang angle provided little soil disturbance while the 10º gang angle provided the most soil loosening.

Seed was mixed directly in the spreader tank and applied with the manure slurry.

Slurry-seeding involved mixing seed in the slurry tank and passing the seed-laden slurry through a rotating chopper/distributor and then through drop tubes to the fractured and loosened soil behind each set of rolling tines. Excess PTO pump capacity provides bypass flow for seed mixing and distribution. Slurry rate calibration is based on tractor engine RPM, travel speed, machine width, and slurry flow rate. A 150 PTO-hp tractor or larger was needed to draw the slurry tank and aeration tool.

Forage rape (Barkant, 6 lb/ac), forage turnip (Pasja, 6 lb/ac), brown mid-rib sorghum-sudan (Sudex, 30 lb/ac) and common oats (64 lb/ac) were sown in untilled wheat stubble on a Capac sandy loam soil on 8 August. Two seeding methods were used: 1) conservation tillage with two passes of a combination tillage tool (12 ft Kongskilde Triple-K, 3-inch tillage depth), and 2) slurry seeding with aeration tillage and seed-laden swine slurry (10 gang angle, 6,000 gal/ac). Fifty lb/ac N as urea was applied to the tilled-and-drilled plots before tillage and planting. No commercial N was applied to the slurry-seeded plots. The sudex and oats were harvested on 21 October and the rape and turnip on 27 October.

Orchard grass (12 lb/ac) and Medium Red Clover (10 lb/ac) were sown in an established brome grass sod using frost, no-till and slurry seeding methods. Frost seedings were done in March. On August 24, the brome grass in one-half of each plot was suppressed with Paraquat dichloride to reduce competition from the existing stand for sunlight and moisture. On August 31, seedings were no-till drilled (Great Plains drill) or slurry seeded (2.5 º gang angle) with 6,000 gal/ac swine manure. No commercial fertilizer was applied to the non-manured plots. Forage yield and quality were evaluated.

What We Have Learned

Slurry seeding late season forages after wheat

The weather was hot and dry in August. The tilled-and-drilled oat stand (43 plants/ft-sq) was significantly greater than the manure slurry-seeded oat stand (24 plants/ft-sq), but there was no difference between the till-and-drilled and slurry-seeded forage rape, forage turnip or sudex stands. Sudex did not establish well with either seeding method. Forage rape and forage turnip yielded greater than sorghum-sudan and oats, but there were no significant differences within a crop due to the seeding method.

Figure 1. Yield of late season grazing crops seeded with swine slurry in untilled wheat ground. Contributed to eXtension cc2.5

Slurry seeding forages in hay ground

Forage yield and quality parameters are under evaluation. Based on preliminary observations:

  • No-till and slurry seeding of red clover in a brome grass sod was more effective than frost seeding in increasing biomass yield and botanical diversity.
  • No-till and slurry seeding of orchard grass in brome grass sod increased botanical diversity but had little effect on biomass yield after the initial N boost. Frost seeding orchard grass had little effect on botanical diversity.
  • The use of a pre-plant burn-down tended to increase weed biomass.
  • The use of a pre-plant burn-down enhanced the inter-seeding of orchard grass, but it did not enhance the stand of red clover.

Forage dry matter yield, Cut 1 2007.

Why is This Important?

Manure slurry-enriched micro-site seeding is an innovative process that combines low disturbance aeration tillage, manure slurry application and the seeding of cover crops in one efficient operation. Manure nutrients collected throughout the winter can be used to meet the nutrient needs of hay and pasture crops but concerns regarding the effect of manure on pasture productivity limit its use. When applied to pasture and hay crop restoration this new process will increase botanical diversity, yield and quality, and provide a more complete, balanced feed for grazing stock. A more complete integration of pasture and manure nutrient management in grass-based systems offers an opportunity to expand the land base for manure application, minimize manure transport costs, improve on-farm nutrient recycling, and improve forage quality and farm profitability.

For More Information

Contact Tim Harrigan, or 517.353.0767. For more information refer to the following article: Harrigan, T.M., D.R. Mutch and S.S. Snapp. 2006. Slurry-Enriched Seeding of Biosuppressive Covers. Applied Engineering in Agriculture 22(6):827-834.

By Tim Harrigan and Rich Leep, Michigan State University

This report was prepared for the 2008 annual meeting of the regional research committee, S-1032 “Animal Manure and Waste Utilization, Treatment and Nuisance Avoidance for a Sustainable Agriculture”. This report is not peer-reviewed and the author has sole responsibility for the content.