On-Site Composting

Composting

Managed decomposition of organic residues to produce a biologically stable material.

Since most organic residues will decompose in the soil without management, it is important to weigh the benefits of making compost

Takes time, labor, and expense

Composting (cont.)

Involves: Collecting and mixing ideal ingredients; monitoring temperature and moisture; turning moistening, or covering the compost production pile (when necessary), to increase the speed of compost production and the quality of the finished compost.anticipated end use of compost determines the level of quality required.Only the highest-quality composts should be used to make potting mixes; lower-quality compost may be suitable for field application.

Ingredients for compost- A good “rule of thumb”

50% brown material (carbon source)

Soil

Dry leaves

Shedded paper & cardboard tubes

Small brush

Old straw and bedding plants

Coffee grounds & tea bags

Landscape trimmings

50% green material (nitrogen source)

Kitchen fruit and veg scraps (no seeds)

Eggshells

Grass clippings

What NOT to put in your compost

Meat or fish waste (raw or cooked)

Dairy products

Oils or fats

Cat or dog litter

Poisonous plants

Weed seeds

Diseased plant material

Constructing a compost pile

Layer green materials and brown materials

Minimum of 3 ft by 3 ft

Best if it can be turned or mixed

Locate in partly shady area but stay away from area under pine trees

Can use compost bins, wire fencing, or open pile

Benefits and Drawbacks of Composting

Well-made, mature compost is probably the ultimate soil amendment.

High-quality compost - benefits of being a source of slow-release nutrients that does not introduce weeds or pathogens.

It improves soil structure and capacity of the soil to hold water and nutrients.

Benefits and Drawbacks of Composting (cont.)

Compost - means of recycling organic wastes for on-site use

Composting can reduce the discarding of bulk materials (kitchen scraps, yard waste)

Evidence that composts can suppress plant pathogens and reduce crop disease.

Less disposal in municipal landfills

Benefits and Drawbacks of Composting (cont.)

The primary drawbacks : management inputs required to make it. Biological process affected by environmental conditions and variable ingredients, consistently high compost quality is hard to achieve.Composts that have not achieved sufficiently high temperatures may contain viable pathogens or weed seeds. Immature compost can continue to decompose, and tie up existing soil nutrients or create compounds harmful to plants.

Benefits and Drawbacks of Composting (cont.)

Fully mature compost usually has low short-term availability of nutrients compared to less-finished compost, since the nutrients have been converted to stable forms that decompose slowly.Although it is necessary to add organic residues to the soil in order to sustain soil fertility, using CC’s and/or animal manures in addition to compost may be a practical choice depending on amount of organic matter available for your compost pile.

Benefits and Drawbacks of Composting (cont.)

On-site composting makes the most sense when:· Free or low-cost, “clean” organic residues are

available on-site or locally.· There’s an appropriate site for stockpiling

materials and making compost.· Equipment for compost production and handling

is available.· A person with compost knowledge is available to provide labor.· Possible objections from neighbors do not pose serious obstacles.

Equipment choices for composting

The Composting Process

Composting : microorganisms that are decomposing.

A process that promotes the number and activity of these microbes is called hot or cold composting, since extensive microbial activity generates heat while it breaks down organic residues.

The composting process

The Composting Process (cont.)Hot composting :requires a couple of months to make high-quality compost, six months is typical when compost piles are turned infrequently. A slower composting process, sometimes called cold composting or passive composting, is acceptable in many situations, although weed seed and pathogen kill will be reduced. In cold composting, conditions are less optimal for microbial activity, and thorough decomposition takes a year or two.With either hot or cold composting, there may be no rush to make compost once several batches at different stages of completion are established—one ready for use that season, and other “in the pipeline”.

The Composting Process (cont.)

Hot composting is primarily an aerobic process, and oxygen is necessary to maintain the aerobic conditions that generate heat and accelerate decomposition.One of the principal goals in managing composting is ensuring adequate porosity for oxygen movement in the pile.The process of passive air movement will ideally replenish the air in the pile several times an hour.

Conditions That Promote Rapid, “Hot” Composting

1. A carbon-to-nitrogen ratio (C:N) of 25 or 30 to 1 on a dry-weight basis

2. Sufficient but not excessive moisture, about 50-60% water by weight

3. Oxygen concentrations over 5% (steady level of 3% may be adequate to limit odorous anaerobic activity)

Conditions That Promote Rapid, “Hot” Composting

4. A pH between 6.5 and 8.55. Internal temperatures of

130-140°F6. Particle size of 1/8-2 inches

in diameter, which provides porosity for oxygen movement and abundant surface area for microbial decomposition

7. Ingredients are well-mixed and piled high enough to retain heat without compacting the pile internally

The Composting Process (cont.)

Cold composting may initially be anaerobic, which in addition to being slower, can generate foul odors. These odors escape when the pile is opened or turned, so if odors are a concern, anaerobic piles should not be turned or opened until decomposition slows and oxygen can slowly diffuse back into the pile.

The Composting Process (cont.)

The ingredients, pile shape and size, turning regimen, and location of the compost should be optimized only so far as makes economic sense.

Composting on vegetable farms/gardens thus ranges from simple, remote piles with very low management to highly managed systems with dedicated equipment and structures.

Most on-farm/garden composting falls somewhere in between these extremes.

Garden composting options

Compost for Greenhouse Use

Compost is often top-dressed on greenhouse crops as a source of additional nutrients and as a medium for adventitious rooting of stems with crops such as tomato.Organic growers rely on compost as an ingredient in potting mixes.Only stable, mature compost should be used for the production of potting mixes to grow bedding plants or vegetable transplants.

Compost for Field UseCompost for field use is buffered by the soil and may be applied within a few months after only a turning or two, depending on the crop to be planted. Some crops, such as corn, tolerate very raw compost as a field soil amendment.In many cases, so-called compost used for field production may be little more than slightly aged manure, managed only enough to improve handling and avoid the likelihood of burning plants.

Compost for Field Use (cont.)

The maturity of compost affects how much can be applied to the field, because care must be taken to not apply excessive amounts of available nitrogen. Although it may be expensive, mature compost may more safely be applied in larger quantities than immature compost.Mature compost contains nutrients in a highly stable form and slowly available to plants.

Testing CompostCompost testing can be simpleObservation. If the answers to the following are yes, the compost is probably mature: Has the pile stopped heating up, even after it is turned? Is it free of off odors? Does the compost appear earthy and uniform in texture?If compost appears to be mature, send a sample to a lab.Determine through testing = C: N ratio, pH, and N levels give some indication of maturity.

Testing Compost (cont.)A high C: N ratio (greater than 25: 1) indicates potential for N immobilization, a characteristic of immature compost that can interfere with plant growth.Extremely high C: N ratio can be improved by further composting, with added N sources or by adding N fertilizer at the time of application.High levels of ammonium can also indicate immaturity and the need for further curing time for conversion to nitrate to take place. Finished compost should have a pH of close to neutral, deviation from this may indicate immaturity. Most agricultural testing labs offer specific compost testing.

Compost as a Nitrogen SourceThe release of N from compost is a less clear matter.Mature compost - release of N may be only slightly greater than that from soil organic matter itself, which each year is only a few percent of the total N it contains.Composts not fully mature probably behave somewhere between soil organic matter and manure.A compost analysis is necessary to get a good estimate of N availability.

Compost as a Nitrogen Source (cont.)Composts with a high C: N (carbon-to-nitrogen) provide very little N to a crop.Composts tend to contain nutrients in the range of 15-30 pounds N per ton, 5-10 pounds P per ton, and 30 or more pounds K per ton, their nutrient contribution can be significant when applied at several tons per acre. Variability of compost nutrient levels makes suppliers reluctant to specify nutrient concentrations, which most states require to assure a consistent synthetic fertilizer industry.

Making Compost TeaThe Pennsylvania Department of Environmental Protection (PDEP) offers a step-by-step processAimed at small growers and gardeners, but it can be adapted for larger plots.Buckets, compost, water and unsulfured molasses (optional food source for beneficial microorganisms)Air pump

Making Compost Tea (cont.)Add compost and water filling the bucket to within 6 inches of the top. (If you are using water from a public water source, let sit for several hours to allow any chlorine to evaporate. Chlorine can kill beneficial organisms in the tea.) Best choice is unchlorinated or rain waterAdd 1 ounce of unsulfured molasses to provide a food source for the beneficial microorganisms. Add air sourceBrew several days mixing occassionallyStrain through cheeseclothCan be foliar applied

Making Compost Tea (cont.)You can put the compost solids back into the compost pile on in the gardenThe tea should smell sweet and earthy. If it smells bad, do not use it. Dump the mixture into your compost pile.

Making Compost Tea (cont.)

Apply the compost tea to your plants immediately. The beneficial microbes will begin to die shortly after the air source is removed.

You can sprinkle the compost tea onto the foliage and the soil around each plant. The tea will provide nutrients and an energy boost.

For more information, e-mail the PDEP at

RA-epcontactus@state.pa.us