Agriculture Reference
In-Depth Information
process generates enough heat to kill many weed seeds, pathogens, and
pests, while still leaving beneficial microorganisms. Raw organic materials
can be sources of diseases, pests, and weeds. Properly composted materials
are also more chemically stable and predictable than fresh materials. If you
use animal manures in your compost, the process allows excess salts to leach
out that might otherwise damage your crop.
And very importantly, good compost has a carbon-nitrogen balance that
is suitable for plant growth — usually around 10 parts of carbon for each
part of nitrogen. Green plant materials, such as green manure crops, are typ-
ically 12:1 to 17:1. Cattle and horse manures have ratios around 18:1. These
materials can be added directly to soils with no fear of creating nitrogen de-
ficiencies in your crops.
Materials that are rich in cellulose, such as straw (80:1) or sawdust
(400:1), have high carbon-to-nitrogen ratios. When these materials are incor-
porated directly into the soil, microorganisms begin decomposing the carbon
compounds. The microorganisms, however, require large amounts of nitrogen
as they form structural and enzymatic proteins. Since the woody material
has little nitrogen, the microorganisms take the nitrogen from the soil itself,
which can create temporary deficits in available nitrogen. Once the microor-
ganisms have completed decomposing the organic material, they die and re-
lease the nitrogen back into the soil. Until that nitrogen is released, however,
your crops can be deprived of adequate nitrogen and suffer stunting or even
death.
OFF-FARM AMENDMENTS
In general, increasing soil organic matter concentrations by adding off-
farm amendments is too expensive in terms of labor and transportation
costs for any but small orchards. In some areas, community waste re-
cycling programs supply mulch from tree trimmings and yard wastes.
