What Is an Amended Soil?

Q. You recommended that to grow a persimmon tree in our area, the soil needs to be amended. What is amended soil? Do you a technique you recommend to amend the Las Vegas soil?

A. Soil is amended by mixing it with something that improves the existing soil in some way. There are a number of amendments available but I prefer compost for most garden soils and fruit trees.

            Compost improves the desert soil chemistry, soil structure and its biological activity. Compost opens the soil improving drainage and aeration as well. Our desert soils have very tiny pore spaces between soil minerals. Larger pore spaces are important for roots to stay healthy. Roots need about an equal mixture of water and air between soil particles.

Desert soils have very small amounts of organic amendments in them making them very poor at growing vegetables

            Compost improves soil chemistry by reducing the alkalinity of desert soils and helps chemicals required by the plant to become more available to them.

Compost added to a vegetable growing area. The compost will be mixed with the desert soil and raised beds will be shaped from this amended soil

            I recommend that existing desert soil be removed from a future planting hole and this soil mixed about half and half with compost. Once the large rocks are removed, this amended soil is used to fill the spaces around plant roots when planting.

            Organic soil amendments like compost disappear in the soil over time so they must be replenished. Replenish soil amendments by adding a 1 inch layer of compost to the top of the soil every year. Compost slowly “dissolves” back into the soil, keeping the soil amended.