SOILS AND FERTILIZERS:
FERTILIZERS
[continued]
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MG
Manual Reference Ch. 2, pp. 38 - 42 |
[Fertilizers:
fertilizers | analysis
| types | organic
| applying |
application | improving |
compost ]
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In special cases, coarse sand, vermiculite, and perlite
are added to heavy clays to help improve the soil texture or
structure. However, these inert materials can be expensive and
large quantities are needed to do any good. In some cases, they
can make the situation worse by causing clays to "set up"
similar to concrete. Compost, manures, and other organic
amendments are more effective and economical for modifying the
soil structure, while leaving soil texture unchanged..
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Organic matter is a great soil improver for both clay
and sandy soils. Good sources of organic matter include manures,
leaf mold, sawdust, and straw. These materials are decomposed by
soil organisms. Various factors such as moisture, temperature, and
nitrogen availability determine the rate of decomposition through
their effects on these organisms. Adequate water must be present,
and warm temperatures will increase the rate at which the microbes
work. The proper balance of carbon and nitrogen is needed for
rapid decomposition. The addition of nitrogen may be necessary if
large amounts of undecomposed high-carbon substances such as dried
leaves, straw, or sawdust are used. In the process of breaking
down the organic matter, nitrogen is used by the microbes and,
therefore, may become deficient in the plants. Fresh green wastes,
such as grass clippings, are higher in nitrogen than dry material. |
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Building a Compost Pile The use of compost is one way avoid tying up nitrogen during
decomposition. Compost is usually made by the gardener from plant
wastes. Correct composting can result in a valuable nutrient and
humus source for any garden. The basis of the process is the
microbial decomposition of mixed raw organic materials to humus, a
dark, fluffy product resembling rich soil, which is then spread
and incorporated into the garden soil. |
Recipe for Composting
When you layer materials in a compost pile
in this order, you will ensure the proportions of carbon and
nitrogen that decay organisms need to work efficiently. You can
repeat these layers to a total height of about 5 feet. The
depression helps retain needed moisture. |
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Start the compost pile with a 3-inch layer of coarse
plant material such as small twigs or chopped corn stalks. This
will aid in aeration and drainage. On top of this, put a layer of
plant and kitchen refuse-leaves, straw, weeds, waste from garden
plants, husks, coffee grounds, crushed egg shells, canning wastes,
etc. It is not a good idea to use animal products except manure
because they will attract digging animals and unwanted insects.
Next, add a layer of nitrogen-rich material. This can be fresh
manure if available, fresh grass clippings (not too thick a layer,
as they will mat) or fresh hay. If you don't have enough
nitrogenous material, there will not be enough nitrogen for the
microorganisms to make proteins. Add more in the form of synthetic
nitrogen fertilizer (1 cup 10-10-10 per 6-inch layer will do),
blood meal (1 cup per 6-inch layer), or cottonseed meal (1 cup per
6-inch layer). The latter two are expensive when purchased in the
typical 5 pound bags available in garden centers, but cottonseed
meal can be found at a very reasonable price in bulk at farm
supply stores. It has formerly been recommended that a 1-inch
layer of soil be added for each 6 inches of plant wastes to supply
microorganisms for the composting process, but research has shown
that this is not always necessary. Enough soil is generally
included on roots of plants and in manure to inoculate the compost
pile. Compost starters are also unnecessary. If the wastes are
free of soil for the most part, however, a sprinkling of soil at
each layering may be beneficial. Repeat the layers of plant
material and nitrogenous material as many times as needed to use
all the plant refuse available. To generate the needed internal
heat, a 3x3x3 foot pile is needed. If you are using a ready-made
composter, follow the manufacturers instructions. |
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Water the pile as often as necessary to keep the
contents as moist as a well wrung out sponge, but not soaking wet.
The top of the pile should be low in the center to cause water to
move into the pile rather than to run off. Within a few days, the
pile should heat up significantly, to about 160 degrees F. This is
a necessary stage in composting, as the temperature will kill many
weed seeds and harmful organisms. If the pile fails to heat, there
is insufficient nitrogen, volume of material, or water in the
pile, and more should be added. The pile will decrease in size
after a few weeks if it is composting properly. If the compost
pile smells like ammonia, it may mean that the materials in the
pile are too tightly packed or that the pile is too wet; i.e.,
there is not enough air. Turn the heap, adding some coarser
material, and start over. |
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The pile should be turned over after about a month (2
weeks if the material is shredded), putting the outside materials
on the inside and vice versa to make sure everything gets broken
down. Turn again 5 to 6 weeks later. The plant materials should
decompose into good compost in about 4 or 5 months in warm
weather, but may take longer under cool or dry conditions.
Composting may be completed in 1 or 2 months if the materials are
shredded, kept moist, and turned several times to provide good
aeration. |
The squeeze test, used to estimate the
moisture content of the compost pile. |
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When compost is finished it will be black and crumbly,
like good soil, with a pleasant, earthy smell. Only a few leftover
corncobs or stalks will remain undecayed. These can be sifted out
and added to the next batch. For use in potting mixtures, a
relatively fine sieve ( 3 / 8 to 1 / 2 inch hardware cloth) will
take out the larger chunks. Otherwise, the compost can be spread
in the garden as it is and dug or tilled under. |
If you need only a small amount of compost, you can use
a plastic trash bag to compost relatively fine material such as
leaves, lawn clippings, or chopped garden refuse. Make layers as
in a compost pile, or mix all materials together. Add 2 quarts of
water to dry material (one quart if it is quite moist or
succulent). Tie the bag and turn it over every few weeks to aerate
the material and distribute the moisture. |
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Cover Crops Another source of inexpensive soil improvement that should not be
underestimated is the cover crop. Green manures, or cover crops
are planted in the garden in the fall for incorporation in the
spring. Any fast growing annual plant that is easily killed will
make a good green manure crop. Choices include annual ryegrass,
wheat, barley, vetch, or field peas. For best results, seed should
be sown as soon as possible after the main crop has been
harvested. In a fall garden, plant cover crops between the rows
and in any cleared areas. Cover cropping provides additional
organic matter, holds nutrients that might have been lost over the
winter, and helps reduce erosion and loss of topsoil. Legume cover
crops can increase the amount of nitrogen in the soil and reduce
fertilizer needs. A deep-rooted cover crop allowed to grow for a
season in problem soil can help break up a hardpan and greatly
improve tilth. Incorporate green manures at least two weeks before
planting vegetables. They should not be allowed to go to seed. |
Carbon to Nitrogen Ratios for Selected Materials (by Weight) |
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Materials with High Nitrogen Values Vegetable Wastes Coffee Grounds Grass Clippings Cow Manure Horse Manure Horse Manure (with Litter) Poultry Manure (Fresh) Poultry Manure (with Litter) Pig Manure Materials with High Carbon Value Foliage (Leaves) Corn Stalks Straw Bark Paper Wood Chips and Sawdust |
12-20 : 1 20 : 1 12-25 : 1 20 : 1 25 : 1 30-60 : 1 10 : 1 13-18 : 1 5-7 : 1 30-80 : 1 60 : 1 40-100 : 1 100-130 : 1 150-200 : 1 100-500 : 1 |
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