Manure and Soil Organic Matter
The use of livestock manure to build up soil health, specifically soil organic matter, is a practice that has been embraced by the agricultural community as well as soil scientists. But a few questions remain to be answered: Is all manure equal? If there are differences, what are they? And, can we use other practices to even out the dissimilarities?
Building up soil organic matter revolves around how much solid material is returned to the soil. Because of this, all manure is not created equal. Even if equal amounts of manure are applied, there will be differences in organic matter production depending on the manure type.
Livestock systems that use solid bedded pack can have a more significant impact on long-term organic matter within the soil. Material with a high amount of lignin, or undigested material, will slowly break down over time into active carbon. This active carbon is very important to a healthy soil. It is where nutrient and aggregate glues are found. It also supplies food for the microbial population. To learn more about the different types of organic matter in soil, take a look at the Michigan State University Extension article Organic matter: The living, the dead, and the very dead.
Farms that use bedding that is low in organic matter, such as sand, will not see as great of an increase in soil organic matter as those farms that use bedding high in organic matter. The chart provided compares common manure types and an average of the dry matter content.
Farms that utilize liquid manures or low dry matter content can still build organic matter by utilizing other farming practices. Implementing minimal conservation tillage and cover crops are practices most frequently and effectively used. Minimal disturbance of the soil, as well as adding nutrients through liquid or semi-solid manure applications, encourage healthy, living organic matter activity in the soil.
Source: Christine Curell, Michigan State University Extension