COMPOSTING & PLANT NUTRITION

Rodale emphasized that the best way to feed the garden was to feed the soil organisms. The soil organisms have a central role in converting materials into plant nutrients, making these nutrients available to the plants, and the overall nutritional process. Feeding the soil organisms means making sure that they have an adequate supply of air, water, organic material, and the various essential mineral nutrients. The process by which soil organisms convert materials into plant nutrients is similar to the process that takes place within the compost pile or bin. This session is about plant nutrition, composting, and the ways compost can be used in the garden.

COMPOSTING:

Mother Nature says that once you are finished using something, you should put it back. Composting is the way Mother Nature processes this returned material. The process is mostly biological. Composting is the collective feeding and digesting of materials by the community of the living organisms. Maintaining a compost pile or bin speeds up the natural process.

USES OF COMPOST:

Compost is a valuable material that does many jobs and does them well. There always seem to be the need for more compost than is available. The uses include:

REASONS TO COMPOST:

It is difficult to make enough compost for the garden. The need exceeds the supply and the temptation is to buy compost from commercial sources. The packed commercial compost that one might buy from reputable garden centers may be completely O.K. regarding ingredients as well as being completely appropriate for the home garden. A lot of the packaged material, however, contains composted sewer sludge which often contains heavy metals that are soil toxic. A lot of the bulk commercial compost is based on commercial or industrial wastes. Again, these material may or may not contain problem materials but there is no good way of knowing. There are no real standards and the contents of commercial composts are not regulated.

Making your own compost from materials collected from your own garden is the best way to regulate the contents. It makes no sense to discard clippings from a clean garden that would make clean compost and to go out and buy the commercial material that may or may not contain problem materials. This is particularly true if the garden is used to grow foods for the table.

Composting is also good citizenship. Anything that we can do to reduce the quantity of material that goes into land fill is a good thing. According to the Los Angeles County Department of Public Works, for example, Los Angeles County disposes of 40,000 tons of waste per day. That's enough to fill Dodger Stadium every 11 days!. 20% of that 40,000 tons is yard waste that could have been composted at home. A 20% reduction in land fill operations would be of huge value to the environment and it would also save huge sums in disposal costs.

COMPOSTING PROCESS:

The processes involved in the rotting or bio-degradation of materials in nature is mostly biological. Primarily, it is living organisms feeding on complex materials and then converting this materials into simpler forms by digestion. Composting is the same cluster of processes but with optimized conditions to speed things along. Specifically, to optimize conditions for the living organisms which means:
  1. Protecting them from the elements;
  2. Protecting them from toxic materials and
  3. making sure that they get enough air, water and nutrients.

PROTECTION FROM THE ELEMENTS:

The composting process generates heat and, in turn, heat hastens the composting process. Composting bins or piles work better when they are protected from chilling winds. As the organisms also do best in moist conditions, they should also be protected from drying winds or from being flooded out.

PROTECTED FROM TOXIC MATERIALS:

The organisms responsible for composting, like all living organisms, are vulnerable to the effects of toxic materials. Just because one can compost almost any organic or mineral thing, it doesn't mean that the organisms can't be injured or destroyed if toxic materials get into the compost bin or pile.

Wood ash, for example, is a rich source for both Potassium and Phosphate. It is also a very alkaline material. A little wood ash would be a worthwhile addition to the composting material but one could add too much and do considerable damage to the ecosystem of the compost pile or bin.

MAKING SURE THEY GET ENOUGH AIR, WATER AND NUTRIENTS:

The compost pile should be turned and mixed about once a week so that the material on the top moves to the bottom and the material on the inside moves to the outside. Turning and mixing the pile lets in the needed oxygen. A compost pile should be kept about as damp as a wrung-out sponge. Proper amounts of air and moisture are necessary for the process to work efficiently.

The key to hot, fast compost is equal parts of "brown" and "green" materials. The organisms that do the work of composting need carbon based materials and nitrogen based materials for their personal diet and for their finished work product. The "green" or high nitrogen materials include: grass clippings, garden trimmings, green leaves, manures and scraps from the kitchen. They are high nitrogen because they contain appreciable amounts of protein and/or amino acids. The "brown" or high carbon materials include: wood chips, sawdust, straw/hay, dried leaves, and shredded paper. They are high carbon because they contain appreciable amounts of cellulose.

Do not put meat, bones, milk or milk products, fat, or dog or cat droppings into the composting pile.

MAKING COMPOST BINS OR PILES:

Ideally, a compost pile or bin should be in a sheltered part of the garden, on level ground with reasonable drainage, and have enough room around it to make it convenient to work. It should have a convenient water source, with good air circulation on at least three sides, and it ought to have one end that can be opened for adding and removing material. It should be able to hold approximately a cubic yard or 3/4 cubic meters. In practice, make it as close to the ideal and convenient as possible.

MAINTAINING COMPOST BINS OR PILES:

"The Rapid Composting Method" by R. Raabe lists the following:
  1. Woody material should be chopped to to 1 inch (2 - 4 cm) bits. Soft succulent tissues need not be chopped.
  2. Carbon-to-Nitrogen ratio in a compost pile should be 30 to 1. A mixture of equal parts of green plant material and dry plant material (dry leaves, woody prunings, straw, shredded paper) will normally achieve this. If the C/N ratio is less than 30 to 1, the compost will give off an ammonia odor. Add sawdust to counteract this.
  3. Do not put soil, ashes from a stove or fireplace, or manure from meat-eating animals in the compost.
  4. A compost pile should be at least 36"x36"x36" (1 meter x 1 meter x 1 meter) to assure adequate heating. Heat retention is better in bins than in open piles. Pile temperature should remain at 160 degrees F. (70 degrees C.) to kill pest organisms. Get a thermometer to check the temperature. Do not let temperatures get more than a few degrees higher; decomposing micro-organisms will be killed. Frequent turning will prevent overheating.
  5. Turn a pile every 1 to 2 days to keep it from getting too hot and to aerate it. Piles turned every day should take about 2 weeks to compost; those turned every two days will take about 3 weeks.
  6. Once the pile is started, do not add anything (unless your compost is not functioning properly and you add sawdust, water or nitrogen as described in numbers 2 or 7).
  7. If temperature do not get up to 160 degrees F (70 degrees C) within 24 to 48 hours, the pile is too wet, too dry, or there is not enough nitrogen (green material). If too wet, spread out the pile to dry. If too dry, add water. If not enough nitrogen, add a material high in nitrogen (grass clippings, fresh chicken manure)
  8. A healthy compost will have a pleasant odor, give off heat when turned, have a white fungal growth on the decomposing material, will get smaller each day, and will gradually change color to dark brown. When no further heat is produced, the compost is ready to use.

SHEET COMPOSTING:

Sheet composting is spreading a layer of extra organic material directly on the bare ground or over a green manure crop. The material is then tilled into the soil and the soil organisms are supposed to take it from there. It is a quick way to add organic material to the soil and it is also relatively easy. It is, however, a good way to spread problems throughout the garden because the organic material does not get hot enough to kill pathogens or weed seeds that might be present.

"GREEN MANURES":

Green manuring is the growing of cover crops to be turned under the soil surface. "The Rodale Guide to Composting" says that green manuring "is the most practical way for the farmer to add substantial amounts of organic matter to land areas. The green manure crop, usually a legume, is most often planted after a food crop has been harvested or as a nurse crop with it, and is turned under about six weeks before the next crop is to be planted."

Sheet composting and green manuring both require that the organic material to tilled or turned into the ground. This is often not practical in the home garden.

VERMICOMPOSTING:

Vermicomposting is composting done with earth worms. It is done in a worm box with drainage holes in the bottom, air holes in the sides, and a light tight cover or lid. The operation is clean, odorless and tidy to the point that the bins are often kept in basements or even inside the house. The purpose of vermicomposting is to generate and collect worm castings which are used as a fertilizer mostly for potted plants. Worm castings are rich in plant nutrients, odorless, and slow release.

Generally speaking, earthworms will eat their weight in kitchen scraps and produce their weight in worm castings every day. Earth worms like soft foods such as cooked vegetables, left over cereal, left over vegetable soup, soft leaves of vegetables (especially lettuce), bread scraps, and even ice cream. Castings are harvested about every three months.

The worms best suited for vermicomposting are red manure worms, Lumbricus rebellus and red wigglers, Eisenia foetida. The night crawlers, Lumbricus terrestris, need cool soil temperatures and don't survive in a worm box. One source for commercial red wigglers, worm boxes and detailed instruction is Down to Earth-Worms in British Columbia, @ 604-374-5718. The best reference is Mary Applehof's "Worms Eat My Garbage".

PLANT NUTRITION:

"The Nature and Properties of Soils" by Brady makes the point that garden soil is an ecosystem and that the things that go on in the garden impact on the way things go on in the soil . . . and that the way that things go on in the soil impact on the way things go on in the garden. In essence, talking about plant nutrition in terms of nutrient management rather than in terms of fertilizer. Brady then lists what he considers as the four major goals of nutrient management:
  1. Cost-effective production of high quality plants
  2. Efficient use and conservation of nutrient resources
  3. Maintenance or enhancement of soil quality
  4. Protection of the environment beyond the soil
Brady seems to repeat Rodale's central theme, "The best way to feed the garden is to feed the soil organisms."

MACRO-NUTRIENTS:

The essential macro-nutrients are frequently divided into three major groups:
  1. NATURAL ESSENTIAL NUTRIENTS . . . those nutrients that are supplied freely by nature in more than adequate amounts; they are materials that are derived from air and water: Carbon, Hydrogen, and Oxygen.
  2. PRIMARY ESSENTIAL NUTRIENTS. . . those essential nutrients that are usually added by the grower and needed in the largest amounts: Nitrogen, Phosphorus, and Potassium
    The numbers on the synthetic commercial fertilizers refer to the percentage content of the primary essential nutrients. The sequence is NPK - the chemical symbols for Nitrogen, Phosphorus and Potassium. (The chemical symbol for potassium is "K")
  3. SECONDARY ESSENTIAL NUTRIENTS: those essential nutrients that are usually added by the grower but needed in smaller amounts: Calcium, Magnesium, Sulfur

MICRO-NUTRIENTS:

The essential micro-nutrients or "trace elements" that are needed by most plants but are only needed in very small quantities; they are usually grouped as cations or as anions

"CHEMICAL" VS. "ORGANIC" FERTILIZERS:

It is obvious from the list of macro and micro nutrients that the CONTENT of fertilizers is clearly chemical. These many chemical elements are essential to the life and growth of the plants. Organic materials such as the various manures, meals, composts, etc. can be analyzed in a laboratory for their chemical content and those same chemical elements are present. The atom or ion of any of these chemical elements is totally the same whether it comes from a synthetic or a natural source.

There are many unanswered questions in plant nutrition but, in essence, the process starts in the roots and not with the fertilizer. Roots exude a goo that is also a nutrient for many of the soil organisms and the goo attracts the soil organisms in large numbers. The goo essentially coats the root surface without going into the soil. The various nutrients contained in the bodies and exudates from the soil organisms becomes incorporated first into the goo and then into the root structures to become nutrients for the plants.

The bottom line is Rodale's original thesis, "The best way to feed the garden is to feed the soil organisms"

ASSIGNED READING: