What to Use When Amending Raised Beds

Q. What should I use to amend raised beds? Mine need to be rejuvenated. Sulfur, rock dust, chicken manure, worm castings, I am not sure which ones to use or to use them all!

Raised beds are probably the best alternative when you are faced with using "fill" that was put in by the developer or builder of the home.

A. There is a lot of hype on the Internet regarding soil amendments. I can understand why it’s confusing. Sulfur, rock dust, coconut coir, worm castings, chicken manure all make promises of miracles.

Stay with the basics if you are just starting out. Amend your soils with compost each year, and your raised bed will be productive every year. The best quality compost is rich in nutrients, consistently black or dark brown in color and a pleasing aroma. Composts that deviate from these characteristics are poorer in quality.

Compost made in Amargosa, Nevada, by a dairy operation using the "windrow" method.

Composts work best if they are mixed with soil.... even desert soil. Many of the subdivisions have extremely poor soils because “fill” was used around the homes rather than soil. In many cases, raised beds filled with soil mixes is the least expensive option to having a garden.

Perlite is one of those amendments used as a soil amendment. It is used mostly for propagation and interior plants.

If compost is applied to these soils every year most of these amendments are usually not needed. Adding compost and growing a productive garden helps to lower its the soil pH so sulfur is usually not needed.

Compost added to the vegetable plots every year at the University Orchard in North Las Vegas

Over a year ago I tested three different rock dusts in several locations around Las Vegas and found no benefit to these additions as long as the garden soil was amended with compost.

The type of compost, whether it is traditional compost or compost made from worms, is up to you and your personal preference. Certainly, if you sleep better at night by adding these amendments to your raised beds by all means apply them. They will not hurt anything as long as you don’t apply too much.

Red wigglers used in worm composting...vermiculture...in a plastic bin and food scraps

Virtually all of the animal manures are effective if they are composted correctly. The only additions I would suggest when first starting off with raised beds are inocula for legumes such as beans and peas.

The type of fertilizers to use are your personal preference but organic fertilizers typically add more to the soil than conventional fertilizers but cost more. However, if your soil is amended properly at the beginning of the season then small amounts of conventional fertilizers would benefit the plants.