Manure is a long-standing soil amendment used to introduce organic matter and nutrients, which are important for establishing a healthy lawn. The question of whether manure can be used when planting grass seed often arises from a desire to improve soil health with natural materials. However, the success of this practice depends entirely on the type of manure used and the method of application. Understanding the distinction between raw and processed manure is the first step in ensuring this organic material helps, rather than harms, a new lawn.
The Suitability of Manure for Seeding
Manure can be beneficial for establishing a lawn, but only if it is fully composted or aged. Raw, or “hot,” manure should never be spread over grass seed. It contains high levels of ammonia and soluble salts that can chemically burn delicate new seedlings, a process often referred to as “seed burn.” Furthermore, raw material is still actively decomposing, and the microorganisms responsible will temporarily draw nitrogen from the surrounding soil, making it unavailable to the germinating grass seed.
Composted manure is a stable, humus-rich material that has already completed the intense decomposition process. This finished product offers a slow-release source of nitrogen, phosphorus, and potassium, which are necessary for strong root development. The composting process also significantly reduces the viability of weed seeds and kills most harmful pathogens. Using composted manure improves the soil’s structure, allowing it to retain moisture more effectively while loosening compacted soil to promote deeper root growth.
Preparing and Applying Manure with Seed
Successful application of manure with grass seed centers on incorporating the material into the soil rather than simply covering the seed with a thick layer. The process should begin by preparing the native soil through dethatching and aerating to improve the exchange of air and water. This preparation ensures the soil is ready to receive the organic matter and allows new grass roots to penetrate deeply.
Composted manure should be applied either before or immediately after seeding, but only in a very thin layer. When mixing it in before seeding, the compost can be tilled or raked into the top one to two inches of existing soil to improve the seedbed. If used as a topdressing after the seed is spread, the layer should be no more than one-quarter to one-half inch thick. This light coverage provides the seed with protection and moisture retention without smothering the emerging sprouts.
Potential Drawbacks and Considerations
Even when using properly composted manure, specific risks can hinder successful lawn establishment. Residual weed seeds are a common concern, as the composting process may not sterilize every seed, potentially introducing unwanted plants. The concentration of nutrients can also lead to nutrient imbalance if too much is applied, especially if the underlying soil already has high mineral levels. A physical drawback occurs if the manure is applied too thickly, forming a dense crust that prevents delicate grass seedlings from pushing through to the sunlight, a condition known as “smothering.”
Herbicide Contamination
There is also a risk of persistent herbicide contamination, where certain herbicides ingested by livestock pass through into the manure and can harm susceptible plants, even after composting. It is important to source manure from suppliers who can guarantee their feed and hay are free of these persistent chemical compounds.
Alternative Materials for Grass Seed Coverage
For homeowners seeking alternatives to manure for covering grass seed, several clean, effective materials are available that provide similar benefits without the same risks. Weed-free straw is a traditional option, offering light coverage that helps stabilize the soil and retain moisture, though it must be spread very thinly to prevent smothering new growth. Sphagnum peat moss is another popular choice, which has an excellent capacity for water retention and creates a fine, light-colored layer that helps keep the seedbed moist.
Commercial seed-starting mixes and bagged topdressing composts are also excellent alternatives, as they are specifically formulated to be free of weed seeds and pathogens. These mixes are typically screened to a fine consistency, ensuring easy, even application that promotes good seed-to-soil contact. A high-quality, screened topdressing compost provides the best combination of moisture retention, light coverage, and a nutrient boost for the emerging grass.