Soil Amendment

March 31, 2021

Soil Amendment - \ˈsȯi(-ə)l ə-ˈmen(d)-mənt/ - noun

Any substance added to the soil to improve plant growth. It can be used to add nutrients, enhance soil structure, improve water retention, protect plants’ roots against pests and disease, or change the soil pH level.

Soil Amendments in the Forest Garden

The main goal, when using soil amendments, is to provide elements for plants that might be missing in the soil or to improve the texture of the soil. There are a variety of types of amendments including chemical fertilizers and organic or natural amendments. There are amendments that are a mix of things, like widely used NPK fertilizers that include variations of amounts of nitrogen, phosphorus, and potassium, and there are amendments that might include one element, like calcium or ash. In the Forest Garden, we encourage farmers to use natural fertilizers rather than chemical fertilizers.

It’s important to match the amendment with the needs of the soil. Charcoal powder is an amendment that can improve water retention as it holds 6 times its weight in water. As such, it may be a good amendment for sandy soils where water filters through too quickly. Ground bones, seashells or egg shells can be used as a calcium amendment. If you have trouble with Blossom End Rot in your tomatoes, you may want to add crushed eggshells to the soil around them, as this disease is a sign of calcium deficiency.  Aged manure or urine can be used as a nitrogen amendment. Any soil will benefit from the addition of organic matter, which is why composting, mulching, and other green manure practices are beneficial. Compost is a “perfect and whole” soil amendment if it combines many of these elements together. The application of compost as a soil amendment builds fertility and soil nutrients, improves soil structure, and improves nutrient and water retention capacity.

Read more about Soil Amendments in Chapter 5 of the Technical Manual here.

Want to learn more about agroforestry? Sign up for our FGTC newsletter here. Plus, join our FGTC Facebook Group to get connected with a global community of agroforesters.