The use of green manures on this continent reached a peak in the beginning of the 20th century, but has declined since the introduction of synthetic inorganic fertilizers. Historically, farmers used green manures as a way of improving soil fertility and increasing crop yields. Improvements in soil tilth that accrued through regular additions of organic matter may not have been as apparent. Effect of Organic Matter on Soil Physical Properties Research during this century has established that organic matter affects some soil physical properties more than others. This review focuses on aggregate distribution and stability, bulk density, moisture retention, and water movement.
Organic matter plays more of a role in aggregate stability than in aggregate formation.
It is, in fact, the primary stabilizing agent for aggregates in temperate-area soils. With few exceptions, organic matter decreases the bulk density of soil. Indirect effects seem to be the most important and are not dependent on soil textural class. Moisture Content and Availability. Soil organic matter has a variable effect on available water in soil.