by Asha Kreiling
Curing compost is the process when heat in the compost pile dissipates and the ecology of the microbe population changes. Certain kinds of soil bacteria, such as azobacteria, take over and produce high amounts of nitrates (which plants need to grow) and balance the carbon-nitrogen ratio of the compost pile, which is important in making nutrients available to plants. Decomposition of the compost material slows down, but continues to occur while the diversity of microorganisms increases.
Using uncured compost can potentially harm plants due to its unstable nature. Uncured compost may contain high levels of compounds like ammonia which can weaken or kill plants, by making soil too acidic. Adding uncured compost to soil can also reduce the amount of nitrogen available to plants, because as microorganisms continue to break down material that has not fully decomposed, they take up nitrogen in the soil for their own growth. In contrast, cured compost contains more nitrate and less ammonia due to longer maturation and mineralization. Cured compost is also more stable, meaning it will not become hot or increase in respiration when watered or turned as unfinished compost does. Phytoxicity, a toxic effect on plant growth, can be caused by compost that is not stable or fully matured. Phytotoxins can cause decreased oxygen and nitrogen levels in the soil, making it harder for plants to grow.
Read back on our old blog on how to cure compost: http://solanacompost.wordpress.com/2009/02/25/rotline-question-of-the-week-what-does-curing-compost-mean/