The number of soil amendments sold in garden centers often confuses gardeners. These products fall into two categories, inorganic and organic. Inorganic amendments come from non-living materials such as sand, perlite, vermiculite and crushed stone. With the exception of limestone and gypsum, used to increase soil calcium, these are not commonly used in the garden.
However, organic amendments are the opposite. They come from previously living materials such as peat, manures and composts. When leaves, bark and animal wastes are mixed together to decompose, compost or "humus" is the final product. Very commonly used, these materials enrich the soil by increasing the air spaces, improving the absorption of nutrients and increasing overall fertility.
Excellent soil is not common around most homes. Even if it was, house construction often removes the good soil and construction equipment compacts the remaining soil. Adding organics loosens compacted soil and results in better gardens. Incorporate organics into the beds throughout the year by working evergreen needles, leaves, and lawn clippings into the soil. Amendments such as peat or lime can improve a pH problem, if one exists. Calcium and magnesium deficiencies can be corrected using organic materials such as bone meal or wood ashes, or inorganic materials such as limestone, gypsum, or soft rock phosphate.
Mulching is another simple way to add biodegradable materials to the soil. Simply place mulch around the plant, leaving several inches from the stem. In addition to slowly providing nutrients as it decomposes, mulching is attractive, reduces weeds and erosion, maintains soil temperature, and prevents “crusting” that occurs when soil becomes too dry.
Another advantage of adding organics is the attraction of worms. They further assist in the decomposition, increase aeration, and leave worm castings. A healthy garden is home to many worms. And it all starts with adding organic soil amendments.