Compost

Technical articles

Organic matter Carbon cycle and GHG Living soils

Composting site

The term "compost" means "compound fertilizer". It comes from a biological process comprising several phases allowing the transformation of organic matter into compost. Agricultural composting allows disposal of agricultural waste, animal manure, carcasses, vegetable waste, hay. Good aeration, good mixing and sufficient moisture are essential for compost.

Manure compost

Manure is not always composted. Here are some arguments in its favor:

• First, manures are often stored in poor conditions. They are rarely protected from rain which leaches a large part of the nutrients.
• Then large piles and stored manure are not turned. Air does not circulate and anaerobic bacteria develop, harmful to soil life.
• Finally, composting manure prevents the germination of weed seeds on the spread plot.

In practice, we do not always have the choice of organic amendments to apply. But knowing their properties allows us to integrate them more easily into the system.

Cattle manure composts

Cattle manure composts with a lot of straw are balanced in C/N. They are therefore an excellent organic amendment. They are also rich in phytohormones which act as bio-stimulants.

Sheep manure composts

They are very rich in nitrogen and thus have a slightly low C/N ratio. They are also more alkalizing than cattle manure and can therefore be interesting on acidic soils.

Horse manure composts

Horse manure composts have a high C/N ratio and resemble plant organic matter. They are very complementary to poultry, sheep, or cattle manure.

Poultry manure composts

They are naturally very concentrated with a low C/N ratio and rich in P and K. They are useful to rebalance soils with a high C/N ratio, but their P concentration can cause blockages. Poultry manure composts contain fruit-setting hormones.

Different composting techniques

There are different ways to produce compost mainly depending on composting time, aeration, etc.

On-farm composting

On-farm composting is an easy-to-implement technique, requiring little equipment and low cost (the cost of the composting operation is similar to that of a traditional manure operation, about €450). Composting allows valorization of agricultural waste and provides a product rich in humus and nutrients, easily spreadable thanks to its homogeneity.

Bokashi compost

Bokashi ("well-fermented organic matter" in Japanese) is a Japanese method of anaerobic composting of organic waste. It has many benefits such as a greater amount of recyclable organic waste, a significant supply of nitrogen and organic matter (OM), and a shorter waiting time before application.

After three days, the farmer can use the liquid phase, called fermentation juice (rich in nitrogenous matter NH4+), as fertilizer and the solid phase of the compost as a source of organic matter and bacteria.

Aerated compost tea

ACT (Aerated Compost Tea) or JCAA (Active Aeration Compost Juice) or also TCA (Aerated Compost Tea) is a liquid rich in microorganisms (bacteria, fungi, nematodes,...) extracted from a good quality compost (or vermicompost) that is multiplied by feeding them with pure cane molasses and other elements according to recipes.

Diluted in water, ACT is sprayed on plants to increase their photosynthetic capacity, vigor and resilience against bio-aggressors and various types of stress.

Applying compost

Incorporation depending on crops

Compost incorporation will depend on the type of crop :

• Annual crops : Spreading before soil tillage and sowing.
• Perennial crops : Spreading before planting or localized application on the inter-row (application from autumn to spring).
• Grasslands : Spreading during the grass growing period.

Dosage

Dosage depends on the starting effluent and crop type :

• Cattle, sheep, goat manure composts : 0-15 tons/ha for a grassland, 15-20 tons/ha for cereal crops.
• Poultry manure composts (very concentrated composts): No more than 5 tons/ha.

Benefits of composting

Recycling and supply of OM

When compost is spread on agricultural land, it increases organic matter content and improves the physical and chemical properties of the soil, which enhances soil structure, nutrient content and pH. Compost can also be an excellent ingredient in growing media (potting soils) for greenhouse production, as it retains moisture and nutrients.

Cost

Low cost, €450 for an on-farm composting operation.

Sources

• Which organic amendments for which properties?, AgroLeague