Manure Spreader Calculator

Start from a manure nutrient test and the crop's nitrogen or phosphorus requirement. The limiting nutrient sets the agronomic rate. In phosphorus-sensitive watersheds, the rate may be set by the soil phosphorus level rather than nitrogen need, which often results in a lower rate.

Yes. Weigh a few full loads, spread a known area, and measure the delivered rate. Spreader output varies with ground speed, PTO speed, apron chain tension, and material moisture. Re-calibrate at the start of each season and when switching manure types.

Keep your rate, total, and spreader capacity all on the same moisture basis. If your nutrient plan specifies dry-matter tons but your spreader capacity is measured in as-hauled (wet) tons, convert before calculating loads. Manure at 70% moisture has a dry-matter content of about 30%, so 10 dry tons equals roughly 33 wet tons.

Apply when runoff risk is low: avoid frozen or saturated ground, steep slopes before rain, and within 100-200 ft of any water body per state setback rules. Fall application on bare ground is high-risk for nitrogen loss over winter. Spring application before planting, or injection into the soil, is the most agronomically and environmentally sound approach.