Composting - Japan - ARI - Introduction to Compost

page developed by Emma Marks, ARI intern from Wilmington College

submitted August 2019

Introduction to Compost at ARI

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The Function of Compost

Compost is one method to supply organic matter to the soil. The main purpose of compost is to turn raw organic matter into humus, which is important for soil fertility and structure. The same thing happens in the forest, but it takes a long time. In compost, organic matter is decomposed into humus more quickly.

Advantages of Compost

Compared with mulch and green manure, compost starts working very quickly – about 10 days after applying. The organic materials have already decomposed during the compost-making process and become a suitable form (humus and nutrients) for the plants. Another advantage is that compost is decomposed completely before using. Applying raw materials can be harmful to the plants and cause pest problems. Finally, any organic matter can be used to make compost, so it is a great way to utilize local resources.

Disadvantages of Compost

The amount of organic matter required – 20 tons/ha, 8 tons/acre

During the composting process, some nutrients are lost because of sun, heat, rainfall, and wind.

Laborious

Materials for Making Compost

The recipe for making compost is very flexible. Almost any organic matter can be used in compost, but it is important to consider the following variables.

Mix dry and wet matter with soil

It is important to mix dry and wet materials with soil in order to provide good conditions for micro-organisms that help decomposition. Aerobic bacteria, which require sufficient air and water, mainly carry out the composting process.

Appropriate ratio: Dry matter (6): Wet matter (3): Soil (1) (Water 50-60%)

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C/N ratio (Carbon to Nitrogen ratio)

All organic matter has a unique C/N ratio. You can control the C/N ratio of your compost by mixing materials with different C/N ratios together. The proper C/N ratio for decomposition and fermentation is between 25-40 parts carbon to 1 part nitrogen.

High C/N ratio – difficult to decompose (ex. Rice straw 60:1)

Low C/N ratio – decomposes quickly (ex. Cow dung 20:1)

Mix materials of high C/N ratio (Rice straw) and those of low C/N ratio (Cow dung) to achieve a balanced ratio (40:1)

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N, P, K (Nitrogen, Phosphorus, Potassium)

Compost can also be a valuable source of nutrients like N, P, and K. The following chart lists some possible sources of these nutrients.

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Free Air Space (Aerobic, Ventilation) & Water

Micro-organisms need water, air and nutrients. Clay soil or wet materials do not have enough free air space. High-density materials also press other materials and decrease free air space. The quantity of air available to micro-organisms depends on free air space. It is necessary to mix light (low density) materials to keep appropriate free air space.

Water is the most important factor for the growth of micro-organisms. Before fermentation 50% water is needed; and then 60%. If water content is less than 40%, the compost ferments very slowly. When turning compost, it is necessary to adjust the water amount.

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Variety of Materials

Not only rice husk and animal dung but also wood ash, mud from ponds, fallen leaves, rice bran, vegetable waste, kitchen garbage, charcoal, human manure, paddy field soil and so on can all be used to make compost.

It is very important to mix many kinds of materials to make compost. This ensures that the compost has rich minerals. If the same kind of compost is used repeatedly, diseases and insects increase.

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Fermentation

A. Why do you need good fermentation?

Putting raw materials directly on the soil will create many problems as the raw materials start to decompose:

A lack of Nitrogen – Micro-organisms consume nitrogen to decompose materials, so applying raw materials may remove nitrogen from the soil.

A lack of oxygen – Micro-organisms consume oxygen from the soil to decompose materials.

Harmful gasses make soil acidic – Micro-organisms produce gasses (Methane, Carbon dioxide, Ammonia) that are harmful to plants while decomposing and make the soil acidic. Ammonia gas and lack of oxygen damages roots.

Retard from absorbing Phosphorus and Potassium

Harmful fungi (Fusarium, Rizokutonia, Pisium etc.) increase and plants' risk of getting sick. As a result, insects attack them easily.

Smell problem and pollution of underground water occurs.

Heavy to carry

B. The process of fermentation

The most important thing to making compost is to grow micro-organisms. Filamentous fungi, yeast, actinomyces, lactic acid bacteria, etc. encourage decomposition. They break down carbohydrates into saccharine. They like saccharides like sugar, glucose, laevulose (Bakuga-tou) and maltose (Katou).

Filamentous fungi and mold (white color) increase on the surface of materials as they start to decompose.

The temperature is 40-50°C. Strong sunlight should be avoided because it disturbs the mold.

The smell is like Japanese sweet wine. If the smell is like vinegar, the compost did not decompose well.

Filamentous fungi make saccharides and dissolves cellulose slowly. Some kinds of microbes (Karekusa-kin) decompose carbohydrates, protein, and fat.

Microbes and mold heat the compost to 60-75°C. If the temperature is too high, nitrogen decreases, so it is very important to turn the pile or add water. Less than 75°C is best.

The smell is like miso and soy sauce.

When the temperature decreases to less than 50°C, lactic acid becomes active and eats the saccharides. If lactic acid acts well, the pH becomes low. After that yeasts start to work, it produces amino acids and protein.

It is necessary to turn compost to make good aerobic conditions for lactic acid.

The smell is like a wine cellar.

Green spots appear at this stage. They are actinomyces. The pH is neutral or a little alkaline. In this stage you can add the powder of rock to supply minerals to the micro-organisms so they become more active.

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C. What is the difference between fermentation and rot?

Both fermentation and rot are caused by micro-organism decomposition. If you find harmful gasses, a bad smell, bad mold and bacteria, which prompts disease, you can call it rot.

If you apply this rotted compost to the field, it is very dangerous and harmful to the plants.

How to Use Compost

A. Growth periods of crops and vegetables in relation to absorption of nutrients

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Komatsuna, Spinach, Turnip, Radish, Cabbage, Lettuce, Chinese cabbage, Broccoli, Cauliflower, Rice, Wheat

Tomato, Cucumber, Eggplant, Hot pepper, Green pea, Soybeans, Soy pea, Strawberry, Sweet corn

Melon, Watermelon, Pumpkin, Carrot, Burdock, Radish

B. Fertilization of vegetables

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