Steer manure is a common soil amendment derived from the waste of cattle, particularly steers raised for beef production. It is highly valued by gardeners and farmers for its ability to improve soil health and fertility over time. This natural byproduct recycles nutrients back into the land, making it a popular choice for enriching garden beds and agricultural fields.
Core Components and Physical Makeup
The physical structure of raw steer manure is primarily a mix of undigested feed, water, and bedding materials. Since cattle are ruminants, their digestive system cannot fully break down the fibrous material they consume. This results in significant amounts of cellulose and other plant fibers passing through the feces, giving the manure its physical bulk and making it an excellent source of organic matter for the soil.
Manure is naturally a dilute fertilizer due to its high water content, which contributes significantly to its fresh weight. Feedlot or barn-collected manure also incorporates various bedding materials used to manage waste, such as straw, hay, sawdust, or wood shavings. These additions contribute carbon-rich organic material to the final product. When introduced to soil, these components improve physical qualities like enhancing water infiltration, increasing water-holding capacity, and improving aeration and structure.
Essential Nutrient Profile
The primary value of steer manure comes from its rich chemical composition of plant nutrients. It contains the three major macronutrients—Nitrogen (N), Phosphorus (P), and Potassium (K)—often referred to by the NPK ratio. The actual nutrient concentration is highly variable depending on the steer’s diet and handling, but it is generally lower than in synthetic fertilizers.
Most of the nitrogen in raw manure is in an organic form, meaning it is not immediately available to plants. This organic nitrogen must slowly mineralize into inorganic forms like ammonium over several seasons. This characteristic makes steer manure a slow-release amendment that feeds the soil gradually, unlike fast-acting chemical fertilizers.
Steer manure contains secondary macronutrients like calcium, magnesium, and sulfur, as well as various micronutrients such as zinc, iron, manganese, and copper. The nutrient profile often contains more phosphorus than crops require in relation to its nitrogen content. This means application rates are frequently based on nitrogen needs, which can lead to a buildup of phosphorus in the soil over time.
Safe Preparation and Application
Raw, or “fresh,” steer manure requires proper processing before it can be safely and effectively used in a garden or field. Fresh manure is high in soluble salts and ammonium, which can damage or “burn” young plants if applied directly. It also contains viable weed seeds that pass through the steer’s digestive tract, along with potential pathogens such as E. coli that pose a human health risk, especially for crops eaten raw.
Composting, often referred to as curing or aging, is the necessary process to stabilize the manure and make it safer for use. Proper composting involves piling the manure and allowing microbial activity to generate high temperatures, ideally between 131°F and 170°F, for a sustained period. This heat is sufficient to kill most of the harmful pathogens and neutralize the viability of weed seeds.
Cured manure has a lower concentration of ammonium and salts, making it much safer for direct application to the garden. If fresh manure must be used, it should be applied and incorporated into the soil several months before planting to allow time for breakdown and for pathogens to die off. For high-risk crops that have edible parts touching the soil, a waiting period of at least 120 days between fresh manure application and harvest is recommended to ensure safety.