I was looking through some posts on the forum. There were some questions regarding the meaning of NPK values.
Homemade Compost NPK= Nitrogen 0.5% Phos 0.27% Potassium 0.87%
NPK values are not the whole story with compost. There is very little NPK value in compost. What compost does do is add and support the soil food web---microorganisms, earthworms and other biota creating a living soil.
Compost contains micronutrients, increases soil tilth, water holding capacity and drainage.
To get good compost what goes in matters. Compost buffers the pH of the soil over time, but compost can vary in pH 6.0-8.5 depending on whether alkaline (comphrey,chicken manure) or acidic materials (pine) are used. Compost naturally cycles through different pH values starting acidic and gradually becoming more alkaline as compost bacteria changes and compost nears the finish.
The mere presence of nutrients in the soil is not enough. Nutrients must be available to the plants. Soil pH matters. Nutrients become more or less available at different levels of pH. All life survives optimally within a narrow pH range.
Most fruits and vegetables prefer a pH range of 6.0 to 7.0 or slightly acidic. There are acid loving plants blueberries, rhodedendron, gardenia, potatoes that like pH 4.3-5.5 and alkaline plants cabbages, baby's breath that like pH above 7.5. Most plants will not grow with a pH less than 3.0 or greater than 9.0.
Below are links expanding on different NPK, Soil and compost topics.
https://www.allotment.org.uk/grow-your-o ... of-manures
https://www.extsoilcrop.colostate.edu/So ... ost_pH.pdf
https://soils.usda.gov/sqi/concepts/soil ... d_web.html