The analysis of compost varies depending on the type of feedstock used to make it and the amount of moisture it contains. Ranges in the table below are estimates based on random testing.
|Type of Feedstock||% N*||% P||% K|
|Poultry manure||2 – 4||1 – 3||1 – 3|
|Feedlot manure||2 – 3||1 – 1.5||1 – 2|
|Dairy manure||1 – 2||0.5 – 1.5||1 – 2|
|Urban yard waste||1 – 1.5||0.2 – 0.5||0.5 – 1.5|
|Crop residue||1.5 – 2.5||0.2 – 0.5||1 – 2|
Once you know the weight per yd3, you can calculate the amount of N, P, or K per yd3. If, for example, your compost weighs 950-lbs/yd3, and it contains 2% N, then:
Keep in mind that the mineralization of N in compost is much more gradual than in a high-protein meal such as blood meal or feather meal. If you’re not sure how much volume you’re spreading, use the Compost Spreading Table to determine the volume being applied.
If more accuracy is require, have your compost tested at a reputable lab. Note: the sample should be tested as compost or manure, not as soil. Compost Submittal Form.