COMPOST QUALITY

The nutrient value of composts varies widely, depending upon the nature of the material being composted. If initial material contains grass clippings, weeds, or manure, it will be richer in nitrogen and other nutrients than if it contains mainly straw, litter, dirt or corn stalks.

The following analyses shows the ranges of values, on a dry basis, in which the chemical characteristics of most finished composts generally lie. These ranges vary because different initial materials will yield final composts of widely varying chemical characteristics.

Substance Percentage by weight:
Organic matter................................... 25.0-50.0
Carbon...............................................8.0-50.0
Nitrogen (as N).................................. 0.4- 3.5
Phosphorus (as P2O5)....................... 0.3- 3.5
Potassium (as K2O)........................... 0.5- 1.8
Calcium (as CaO).............................. 1.5- 7.0

Composts also contain a great variety of micronutrients. Since organic materials for composting contain products of agriculture or horticulture, it is logical to expect these nutrients to be present in the compost. Experiments indicate that compost manures have beneficial effects greater than those to be expected from nitrogen, phosphorus, potash, and humus content alone.