Chicken litter, a mixture of poultry manure and bedding material (like wood shavings or straw), is a valuable organic fertilizer source for hay production. It provides essential nutrients, improves soil health, and boosts forage yields for grass hay crops. Determining the correct application rate requires balancing the field’s demand with the litter’s nutrient supply to maximize benefit and prevent environmental concerns.
Understanding Chicken Litter Composition
Chicken litter contains significant amounts of nitrogen (N), phosphorus (P), and potassium (K). The fertilizer value is often estimated to be around a 3-2-2 ratio (N-P₂O₅-K₂O). For example, a typical ton of broiler litter may contain approximately 63 pounds of nitrogen, 61 pounds of phosphate (P₂O₅), and 50 pounds of potash (K₂O), though these figures vary widely.
The nutrient content depends heavily on factors such as the type of bird, the feed composition, the amount of bedding material used, and the moisture level. Because of this variability, a laboratory analysis of the specific batch of litter is the only reliable way to determine its exact nutrient concentration. Without an accurate analysis, the application rate is an estimate, risking under- or over-application of nutrients.
A significant portion of the nitrogen exists in organic forms, which are not immediately available to the hay crop. Soil microbes must convert this organic nitrogen into plant-available inorganic forms through mineralization, a process influenced by soil temperature and moisture. This slow-release nature provides a steady supply of nitrogen throughout the growing season, but it makes calculating the immediate Plant Available Nitrogen (PAN) more challenging.
Assessing Hay Crop Nutrient Requirements
Calculating the correct application rate begins with assessing the nutritional needs of the hay crop and the existing soil fertility. Soil testing is the first step, establishing baseline levels of phosphorus, potassium, and pH in the field. Soil test results provide the specific fertilizer recommendations required to achieve a realistic yield goal for the forage being grown.
Different hay crops remove varying amounts of nutrients. For example, a high-yielding Bermuda grass field may remove up to 400 pounds of nitrogen, 90 pounds of phosphate, and 345 pounds of potash per acre over a season of multiple cuttings. A ton of general grass hay typically removes 50 pounds of nitrogen, 15 to 20 pounds of phosphate, and 45 to 60 pounds of potash.
The application rate must be sufficient to replace the nutrients removed with each cutting and maintain soil fertility. However, chicken litter supplies nitrogen and phosphorus in nearly equal amounts, while grasses require three to four times more nitrogen than phosphorus. Applying enough litter to meet the nitrogen demand often results in a significant over-application and buildup of phosphorus in the soil.
This excessive phosphorus accumulation is an environmental concern because it can lead to runoff into surface waters. Therefore, application rates are often limited by the phosphorus limit necessary to protect water resources and comply with nutrient management regulations, rather than the nitrogen requirement. Growers with high soil phosphorus levels must apply litter based on the P-requirement—which undersupplies nitrogen—or use alternative nitrogen sources.
Calculating the Optimal Application Rate
The optimal application rate matches the crop’s nutrient needs (from the soil test) with the Plant Available Nitrogen (PAN) supplied by the litter. To estimate PAN, the total nitrogen must be adjusted for losses due to volatilization and slow mineralization. For surface-applied litter, only about 50 to 70 percent of the total nitrogen is typically available to plants in the first year.
A common starting recommendation for grass hay is 2 to 4 tons of chicken litter per acre. This range provides a nitrogen boost, but depends on the litter’s nutrient analysis and the yield goal. For instance, if a ton supplies 30 pounds of available nitrogen, a 4-ton application delivers 120 pounds of nitrogen per acre, sufficient for a moderate grass hay yield.
To manage phosphorus, many nutrient management plans limit application to the phosphorus removal rate of the hay crop. If a hay crop removes 90 pounds of P₂O₅ per acre, and the litter supplies 61 pounds of P₂O₅ per ton, the application is restricted to approximately 1.5 tons per acre. This restriction prevents phosphorus buildup but requires supplemental commercial nitrogen to reach the desired yield.
The most accurate calculation uses the actual litter analysis and the soil test to create a nutrient budget. This budget determines the application rate based on the required nitrogen or the allowed phosphorus, whichever is the lower number. Nearly all the potassium (90 to 100 percent) in the litter is immediately available, which is beneficial since hay removes large amounts of potassium.
Practical Timing and Handling Guidelines
Effective use of chicken litter depends on proper timing and handling. The ideal time to apply litter is immediately before the crop’s period of active growth to maximize nutrient uptake and minimize loss. For cool-season grasses (like fescue), this means early spring or fall, while warm-season grasses (such as Bermuda grass) benefit from application in early spring or immediately following a cutting.
Avoid applying litter during dry, hot, or windy conditions, as this increases nitrogen loss through volatilization. The best practice is to apply the litter just before an expected rainfall, which washes nutrients into the soil and reduces gaseous losses and runoff risk. Uniform spreading is crucial; improperly calibrated spreaders cause uneven growth and inefficient nutrient use.
Environmental safety regulations mandate specific setbacks to protect water bodies. Litter should not be spread within 100 feet of wells or surface water without a permanent vegetative buffer, and a 35-foot setback is often required even with a buffer. Additionally, litter should never be applied to frozen or saturated ground or on steep slopes, due to the high risk of nutrient runoff.