Does Compost Need to be Turned?

There are many advantages of a good manure compost:

• reduced/eliminated pathogens
• reduced viable weed seeds
• reduced insect larvae (fly problems)
• reduced odour
• reduced volume and moisture content
• stabilized organic components and nutrients
• production of a soil amendment/fertilizer

To accomplish these advantages you need:

• the correct carbon to nitrogen ratio (25:1 to 35:1),
• to maintain proper moisture levels (40-60%), and
• the ability for air to travel through the composting materials.

Windrow Management

Turning the compost pile with a compost turner or a front-end loader can allow you more opportunities to "manage" the windrow or pile. Several turns in the first two weeks will get temperatures up to optimum. This will quickly reduce odours and the potential for flies, which is particularly beneficial if there are neighbours nearby. Turning will also reduce pathogens and effectively reduce your risk of potential problems if the site is tile drained or near water sources.

Windrows that are not turned can dry out at the surface and concentrate water near the middle. Uneven moisture content will reduce the temperatures and the overall effectiveness of the composting. Turning will make the windrow more uniform. Turning can help to reduce moisture if it is too high, or allow an opportunity to add moisture if the windrow is too dry.

Composting requires oxygen. Turning will add lots of oxygen initially to the windrow, but an active windrow will use up this oxygen within 1-2 hours. The air spaces created by the turning must be complemented by sufficient porosity of the materials to allow air to continue to diffuse naturally into the windrow. Windrows must not be too large, as this air will generally only travel 1-2 metres through the compost material. Turning too frequently will breakdown the compost materials excessively and reduce the ability of air to diffuse through the compost.

Organic Standards

USDA (NOP) standards require windrow compost to reach 131°-170°F (55-76°C) for 15 days and to be turned 5 times during this time. The Canadian organic standards are similar. The temperatures for in-vessel composting are more uniform and need to be held at 55°C for three consecutive days. The temperature known to kill most pathogens when they are exposed for three days is 55°C. In windrows only the core reaches these temperatures, so the compost needs to be turned 5 times to make sure that all materials are exposed to the high temperatures.

When using a front-end loader take care to clean fresh manure from the loader before turning the compost. When turning, try to turn the outside of the old windrow into the middle of the new windrow to make sure that all materials reach high temperatures to get good pathogen and weed seed kill.

Weed Seeds & Pathogens

These high temperatures will also kill most weed seeds. If the windrow is not turned the pathogen and weed kill will be variable. Solid manure that is left to decompose aerobically without turning will breakdown and most pathogens will eventually die if the pile is left for more than one year. Unfortunately, on many sites this allows the potential for leaching and other adverse environmental and health risks. Under the Ontario Nutrient Management Act these nutrients cannot be left stored in the field more than 300 days (may be less depending on the various site conditions). The challenge is to be able to make good compost without it costing a lot of money or time. Front-end loaders take more time and labour. Compost turners do a better job, but cost more initially. Costs can be reduced if several farmers can get together to share a compost turner.

Related Links

• Organic Crops

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