Getting Down and Dirt With Organic Compost

The growing concern about environmental issues and unhealthy soil has induced extensive use of compost in agriculture. There are compelling reasons that make compost a better alternative to support agricultural crops production, increase yields and enrich the quality of produce. The sum of those reasons is this: compost makes soil healthy.

The key to having good soil health — and, therefore, crop health — is to make sure it is biologically active. Only composted material can help you do that; according to several studies, the use of chemical fertilisers contributes significantly to soil deterioration.

One of the best ways to produce biologically active compost is by thermal aerobic composting. Aerobic composting means that the decomposition of organic matter is done by the microbes (e.g. bacteria and fungi) and small invertebrates (e.g. worms), which thrive best when there is enough air in the compost pile to provide oxygen of at least 5% (freely circulating air has approximately 21% oxygen). The thermal effect in the compost comes from the biological activity of the microorganisms, which can make the pile heat up to as much as 160°F (71.1°C).

The action of these aerobic microorganisms results in a rapid and very effective composting process. The temperature level of the compost indicates the rapidity of microbial activity, since microorganisms actively decomposing the organic matter generate heat. Temperatures ranging from 90° to 140°F (32.2° to 60°C) indicate that decomposition is happening at a fast rate. Above 140°F, the microbes tend to slow down and die off, so pile temperature should be kept below this threshold.

The aerobic bacteria that constitute the most effective agents for decomposition thrive in the moderate temperature range of 70° to 100°F (21.1° to 37.8°C). Temperature can be managed by making sure there is sufficient aeration in the compost through regular turning of the pile and monitoring of the moisture content. Aeration decreases substantially if the mixture gets water-saturated, leading to anaerobic conditions.

For purposes of soil health, you do not want the anaerobic (i.e., without air) microorganisms doing the composting because anaerobic decomposition leads to a badly-smelling compost pile and a higher moisture content (in excess of the acceptable 40-60%). Aside from the offensive odours produced, excess moisture leads to significant loss of nutrients in the compost due to leaching.

Compost should not contain any toxic substances such as heavy metals and anaerobic compounds. The carbon-to-nitrogen ratio should be no higher than 17:1 — when carbon is too high, the decomposition may have been too slow or not yet complete; when nitrogen is too much, the compost could still produce ammonia and emit foul odours. Properly composted material will also have a high proportion of humus to the overall organic matter content.

It is important to get the best quality of compost for your farm. Although there are minimum quality standards for compost, the industry is basically self-regulated. This means that organic farmers who want to be reassured about the quality of compost should obtain an independent laboratory analysis and a list of ingredients used in the compost.

If your compost is of the right quality, it can help improve the structure of the soil in your farm, facilitate nutrient cycling, and reduce, if not eliminate, the need to use various chemicals. Overall crop health will therefore be much better with good compost, leading to healthy yields. On the other hand, composts which do not meet the quality specifications could actually harm farm soils or crops. You know which one you need for your farm.