Below is a list of soil amendments that you can choose from to layer on or dig into your soils. Factors to consider in selecting soil amendments and mulches are the availability, cost, ease of handling, and pH range of the materials.

Compost: Finished compost is an excellent soil amendment. You can make it yourself or buy it commercially. Finished compost is well on its way to becoming stable humus. When mixed into the soil, it resists compaction and drains quickly, yet still retains an enormous amount of water. Compost will retain ten times its weight in water. It also serves as fodder for the “micro-herd,” the soil microorganisms that break organic material down into nutrients in a form readily taken up by plant roots.

Shredded leaves: If you don’t have enough compost to feed all the soil in your yard and garden, chopped leaves are a good second choice. They are cheap, readily available, and easy to use. Remember to chop or shred the leaves before using them as a mulch or soil amendment. Whole leaves blow away easily when dry, and after wetting can form a crusted mat that keeps almost all moisture from seeping through to the soil underneath. If you incorporate whole leaves into the soil, they will take much longer to decay than chopped leaves. If you don’t have a shredder, you can shred your leaves with a lawn mower. Run the mower repeatedly over a pile of leaves, criss-crossing the leaves until only small pieces remain. Most leaves are acidic, but will not add enough acidity to significantly affect soil pH. Pine needles are even more acidic, and may reduce soil pH.

Grass clippings: Grass clippings are a good organic mulch for flower and vegetable beds. Leaving grass clippings on the lawn not only builds the humus content of the lawn soil, but also adds nitrogen, reducing lawn fertilizing needs by as much as 30%. If you mow frequently, the clippings will fall down among the grass plants and never show. The only times you should rake off grass clippings are if your lawn has a thatch accumulation problem, or if you have mown very tall grass. Dense clumps of long clippings could shade out portions of the turf. If you do rake off lawn clippings, use them as mulch or add them to the compost pile. The
nitrogen content of grass clippings is high, and almost immediately available.

However, they will not last more than a few weeks as a mulch. Grass-clipping mulches work well around nitrogen-loving vegetable crops like spinach and lettuce. Because you can adjust the depth of this mulch so easily, you can spread a thin layer around plants while they are still quite young. Leave a little open space around each plant, because fresh grass clippings can give off enough heat as they rapidly decompose to burn vegetable and flower transplants. You may use grass clippings to help fertilize your lawn or to mulch your vegetables. If you’re selective in your use of lawn clippings, you might be able to pull off both.

Aged manure: Aged manure is a great soil amendment. It adds material well on its way to becoming humus and is a significant source of nutrients. Unfortunately, animal manure is not readily available to most home gardeners. If you can get manure, add it to soil only after it
has aged for at least six months.

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