Soil amendments are materials which are worked into the soil to enhance the soil’s physical properties. Good soil is the foundation of every successful garden. Unfortunately few gardens come with soil that is ideal for growing plants; nutrient-rich, well-draining, while still holding water long enough for plant roots to access it, creates a nice, crumbly tilth. Since gardeners cannot count on nature to supply all the essentials, they will have to be added by the gardener. That's where soil amendments come in.
There are several reasons soil amendments might be recommended for your garden or lawn. The two most common are to improve the soil's texture and to correct the soil's pH.
Improving Soil Texture
Often soil is low in organic matter, necessary for the structure, water retention and life of your soil. Organic matter includes compost, composted manure, peat moss, coir, leaf mold, and any other plant or animal remains or waste products. This may not sound like something that would be good for your garden, but organic matter can quickly change the texture of your soil as well as encourage beneficial organisms to set up home in your garden soil.
Adjusting Soil pH
You might also add amendments to alter the soil's pH. The pH of the soil needs to be within a range that will allow plants to access the nutrients in the soil. Some plants prefer slightly acidic or alkaline soil and many require soil in the neutral range of about 6.5 to 6.8. You will need to test your soil to determine what its current pH is. You can buy a kit for this at most garden centers or you can have it tested at your local cooperative extension office for a nominal fee.
Once you know what your soil pH is and what range your plants prefer, you will get instructions on how much lime to add, if your soil is too acidic or how much sulfur to add if your soil is too alkaline. Ideally, you should test your soil every year.
Garden soil is always in flux. Plants deplete it of nutrients, rain washes them away and even heavily amended soil will eventually revert to its natural state. You will need to amend your soil regularly. How often will depend on the soil you are starting with. Once you get to know your garden soil, you will have a better sense of what amendments your garden will need.
The best practice you can get into is using organic matter in your garden whenever possible, and the easiest way to do that is to start and use a compost pile. Put those pulled weeds, vegetable peelings, and garden debris to good use. You probably won't be able to make enough compost for all your needs, but it's a good start and it's free.
Composted materials won't necessarily add much in the way of nutrients, but they will encourage a balanced ecosystem that will keep the nutrients and soil pH in check while they improve the texture and drainage of the soil.