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Composting

Composting and compost:

All organic form waste , stubble of crop, waste straw sweepings, threshing, floor collection, weeds etc may all be collected and used for augmenting the organic matter supply, they can not be used directly as manure, in most cases and required to be decomposed before application. The process of decomposing organic waste is called composting and the decomposed material is called compost.

Compost pile:

Due to composting C:N ratio become form 14:1-20:1 and CEC becomes 50-70 cmolg^-1 of compost though 50% of carbon is lost as CO₂, but most of the nutrient remain in the bulk of the compost.

Pits usually 3×4×1 m deep and dug with aloping sight and till with organism such as straw, leaves. Length will varies by 1.5 m/.

Usually dry organic wastes are lead in pit in layer one after another moistened with water in suspension with cow dung. When a manure filled to it’s capacity the manure may be protected by covering a thin layer of soil, usually 3-5 cm thick. This will reduce the expose of the manure to the atmosphere and consequent aeration.

Composting process:

# Compost refers to the organic residues or a mixture of organic residues and soil, that have been piled, moistened and allowed to undergo biological decomposition.

# Composting is the time honored practice of encouraging partial rotting by MO and other soil organism of organic materials of either plant or animal origin.

# Composting is the practice of creating humus like organic materials out side of the soil by mixing, piling or storing organic materials under conditions suitable for aerobic decomposition and nutrient conservation.

# The main difference between humus and compost is, In composting decay occurs outside of the soil and generate considerable heat.

Process:

Sufficient mass of organic material is kept on Moist condition and Well aerated.

Three stage decomposition.

1. Mesophilic stage:

-This is the first stage of decomposition.

Sugars + microbial food sourcesà rapidly metabolized

Produce

Temperature in compost pile

Temperature gradually rises to 40⁰C.

2. Thermophilic stage:

- After one or two weeks

- Temperature rise from 50 to 75⁰C

- Cellulose and other resistant materials are decomposed by thermophilic bacteria.

- Frequent mixing is necessary to supply O₂

- Assure heating, artificially ( if needed)

- Humus like compounds are formed during this stage.

3. Second mesophilic or crusting stage:

- The temperature falls back to near ambient

- Mesophilic organisms including beneficial organisms are activated.

- They produce plant growth stimulating compounds.

- Or are antagonistic to plant pathogenic fungi.

- Stage lasts from several weeks to several months.

- Mesophilic fungi Aspergillus nigar or Penicillium sp. acts as catalyst.

- Aerobic process.

CH₃COOH +2O₂------2CO₂+2H₂O+energy (by enzyme in oxidation process).

-Anaerobic process

4C2H5-COOH+2H₂O----------4CH3-COOH+CO₂+3CH₄ (in presence of bacteria)

CH3-COOH ----------- CO₂+ CH₄

Characteristics of compost

1) Content of non humic substances declines and content of humic acid increases.

2) The C/N ratio of organic materials decreases. 14:1 to 20:1

3) CEC of OM increases to about 50 to 70 C mole/ kg of compost.

4) 50% or more carbon in the initial stage is lost during composting.

5) Mineral nutrients are conserved.

6) Finished compost supply more nutrients than initial condition.

7) It helps in building soil fertility.

8) Compost is free of weed seeds and pathogenic organism (destroyed in thermophilic stage)

9) Finished compost supply more nutrients than initial cond.

10) Composting can’t destroy heavy metals from soil.

11) Compost----à low phosphoric acid.

Field application + super phosphate —> phosphoric acid is highàP

11) Minimize the fixation of phosphorus in the soil.

12) Used as mulch.

13) Acts as a slow release fertilizer.

14) Acts as an organic conditioner.

Benefits of composting:

Though making compost is expensive and needs hard work, the process has at least 7 distinct advantages.

1) Safe stage:

- Composting provides effective and safe storing of organic materials.

- Convenient to apply them to soil.

2) Easier handling:

- CO₂ is lost from composting, so volume reduce to 30 to 50%

- For smaller volume and greater uniformity it is easy to handling.

- Eventual use of OM as soil amendment or potting medium.

3) Nitrogen competition avoidance:

- In compost primarily there is higher of C/N ratio.

- With time C/N ratio decreases.

- For the depression of Nitrate in soil, avoid indirect induced plant nutrient deficiency for compost.

4) Nitrogen stabilization:

-Reduce Nitrate leaching from organic waste.

- When applied to the soil, composted materials decompose and mineralized much more slowly than uncompost.

- Composing that has low C/N ratio with high C/N ratio materials (saw dust, wood chips) Provides sufficient carbon for microbes to immobilize the excess N_2.

- Provides sufficient N₂ to speed the decomposition of high C/N ratio materials.

5) Partial sterilization:

- In thermophilic stage-à high temperature is produced

Kill most weeds

Kill pathogenic organisms.

-If temperature 40-50⁰c then many weeks or months needed to achieve same result.

6) Detoxification:

- Toxic compounds in organic wastes (Pesticide, phytotoxic chemicals) can be treated by compost

7) Disease suppression:

-Composts encourages antagonism and controls soil borne plant disease.

- In the time of field application it also suppress diseases.

Besides these:

1) Compost supplies nutrients particularly NH₄-N

2) Greater movement and availability of P and micro nutrients.

3) Increases moisture retention.

4) Improves the movement of air and water in soil.

5) Cohesion in sandy soil and improves water holding capacity.

6) Improves infiltration—>decrease bulk density.

7) Increases pH and buffer capacity, through complexation of Al³⁺ in acid soil.

8) Provides food for soil microbes—>MO liberate plant nutrients for soil.

9) It increases soil OM.

How to make compost - compost pile