Think Globally
Chemical Benefits of Compost
Modifies and Stabilizes pH
The addition of compost to soil may modify the pH of the final mix. Depending on the pH of the compost and of the native soil, compost addition may raise or lower the soil/compost blend’s pH.
Therefore, the addition of a neutral to slightly alkaline compost to an acidic soil will increase soil pH if added in appropriate quantities. In specific conditions, compost has been found to affect soil pH even when applied at quantities as low as 10-20 tons per acre.
The incorporation of compost also has the ability to buffer or stabilize soil pH, whereby it will more effectively resist pH change.
Increases Cation Exchange Capacity
Compost will also improve the cation exchange capacity of soils, enabling them to retain nutrients longer. It will also allow crops to more effectively utilize nutrients, while reducing nutrient loss by leaching.
For this reason, the fertility of soils is often tied to their organic matter content. Improving the cation exchange capacity of sandy soils by adding compost can greatly improve the retention of plant nutrients in the root zone.
Provides Nutrients
Compost products contain a considerable variety of macro and micronutrients. Although often seen as a good source of nitrogen, phosphorous and potassium, compost also contains micronutrients essential for plant growth.
Since compost contains relatively stable sources of organic matter, these nutrients are supplied in a slow-release form. On a pound-by-pound basis, large quantities of nutrients are not typically found in compost in comparison to most commercial fertilizers.
However, compost is usually applied at much greater rates; therefore, it can have a significant cumulative effect on nutrient availability. The addition of compost can affect both fertilizer and pH adjustment (lime/sulfur addition).
Compost not only provides some nutrition, but often makes current fertilizer programs more effective.
© 2000, Jim McNelly