Soil amendments are used to improve the condition of the soil in terms of its ability to retain water and nutrients, as well as its aeration and water penetration. Soil quality deteriorates due to erosion and fast agriculture cycles, leaving the top soil stripped of nutrients. You choose the right soil amendment depending on what your current garden soil needs. You need to know your garden soil profile: its texture--whether it is sandy or mostly clay; its salinity or salt content; and its acidity or pH level. There are plants that are sensitive to certain minerals and salts, and grow better on a certain pH level, so you also choose the soil amendment depending on which plant or tree you are growing. You can ask help in testing your soil to find out its profile.
The use of a soil amendment contributes to soil conservation. These are some of the major considerations in choosing soil amendments:
- Organic amendments are materials from plants and animals such as grass trimmings, saw dust, animal manure and vegetable peelings. These are usually made into compost first before being used in garden soil. Organic amendments increase the nutrient content of the soil, and it also helps increase the ability of the soil to hold water.
- Inorganic amendments come from man made materials and things from rocks such as gravel, sand, rubber chunks from tires, perlite and vermiculite. Inorganic amendments help loosen the soil to allow water penetration and aeration.
- It is best to understand how each type of organic soil amendment will benefit the soil and the plants. The most common organic soil amendments are compost, manure, wood byproducts and peat. Compost is mainly food waste that is combined with soil to decompose. Compost can also contain inorganic materials like crushed sea shells.
- Peat is similar to compost, but is naturally composted in wetlands and forests where vegetation gets dried up, rained on and naturally decomposes until it becomes a mass of composted material. These are usually collected and used not just for soil amendment, but also for fuel because of their carbon content.
- Manure is also mixed with soil to decompose. It is advisable to "age" manure before using in gardening (around 6 months) because fresh manure have high levels of ammonia, which can harm the plants. Take note that manure has high salt levels, so do not use this if your garden soil is already high in salt content.
- Wood products like sawdust or wood ash can also be used. It should be noted, however, that while the wood decomposes, the bacteria consumes nitrogen, meaning the nitrogen content of the soil amendment decreases because it is used up by the bacteria that breaks wood down into soil. You may have to use additional nitrogen supplements for your garden soil if you will use wood products.
- Sandy soil needs more compost or peat to help it retain more water. If you are gardening on clay, then more inorganic material and some compost is useful to improve water penetration and aeration. If the soil has high salt content and/or pH level, add compost or peat to amend the soil. Otherwise, wood ash is a good way to increase salt content and pH level.
- If you are planting vegetable and root crops, it is not advisable to use manure as an amendment. Instead, use compost or peat. Manure is okay for flowers and ornamental plants.