Organic farmers know that adding compost to the soil increases the quality and yield of agricultural crops. This phenomenon is generally attributed to the mineral content of the compost which decomposes and allows its organic mineral content to become available for uptake by the plant roots. However, what is generally not recognized is the fact that organic matter in the soil, such as compost, gives off carbon dioxide as it decomposes in the soil, and that this carbon dioxide is readily available to the plants for use in the photosynthesis process. Part of this carbon dioxide given off by the decomposing organic matter may be absorbed directly by the plant roots and part may be absorbed through the plant leaves. In either case, the external carbon dioxide provided by the decomposing compost will help plants grow faster.
Healthy soils have more organic matter and give off more carbon dioxide than unhealthy soils.
This phenomenon is the basis for a soil health test that evaluates the vitality of a soil sample by measuring the rate at which the soil gives off carbon dioxide. The healthier the soil is, the faster it gives off carbon dioxide. The above article referenced in Scientific American presents some of the latest scientific thinking regarding the atmosphere and the growth of vegetation. Previously, scientists thought that trees obtain most of their nutrients from the soil. However, they have come to realize that trees obtain most of their nutrients from the minerals dissolved in rain water and from the dust particles entrained in precipitation.