quality of composts
The nutrient value of composts varies widely, depending upon the
nature of feedstock 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 analysis 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.
Quality compost also contains many organisms necessary for soil
health. Depending on feedstock, weather and type of process used,
each batch will have different organisms. This composted organic
matter, when applied to the soils provides a necessary source of
energy and food for the soil organisms, as well as essential nutrients
for plant growth.
Think of the soil not only as a physical and chemical substrate,
but as a living entity. When making quality compost you can manage
the soil organisms as a high value “mini-livestock.”
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