What is a soil amendment? Soil amendments are materials added to change the condition of the soil to improve its physical properties, with the goal of creating a better environment for root growth. Amending the soil is not the same as mulching, which takes place on the surface of the soil or fertilizing, which amends the soils nutrients. Amendments must be thoroughly mixed into the soil to maximize its effectiveness. Remember the goal here is to improve permeability, drainage, structure, aeration and water infiltration.
How do you know when amendments are needed? Unless you are Johnny-on-the-spot and do a soil test before you start planting you wouldn’t know. From personal experience: As soon as I moved to the country I knew I wanted a garden. I tilled and planted, and everything grew well my first year. I thought I was an expert! The second year was a different story. I didn’t do anything different from the previous year, I just threw the seeds in, watered and waited to see what happened! That year, half of my garden produced, and the other half looked as if I had drawn a line and sprinkled “don’t-grow” dust! As it turns out I was not an expert! This is where the soil testing proved to be invaluable.
Soil testing is a valuable tool; it will determine the amount of nutrients available in your soil and your soil type. In my case, the soil was very high in potassium and phosphorus and was pretty much a flat-line on nitrogen. My soil structure was good, meaning I didn’t need to add inorganic type amendments. My report also showed that my organic material was right on target as were the other minerals noted. Once I had the soil data I was able to move forward making the recommended amendments in my garden site via a nitrogen only fertilizer.
Amendments fall under two broad categories, organic and inorganic, and there are many options. Organic amendments are typically derived from something that was alive, such as grass clippings, manure, compost or peat. Organic amendments will increase the organic matter in the soil and offer many benefits, as they contain plant nutrients, act as organic fertilizers and provide a source of energy. Plants rely on 17 nutrients for normal, healthy growth. These are referred to as “essential nutrients” because plants cannot survive without them; they are critical in the success of your lawn/garden and ornamentals. Inorganic amendments are mined or man-made and can include, sand, pea gravel, perlite or tire chunks. Inorganic amendments will change the soil to improve structure, drainage and aeration.
Determining your soil type — clay, sandy or silt — will assist you in choosing what is best. For example, adding sand to clay soil will create a profile similar to concrete. Some examples of effective physical soil improvements are: compost and peat moss for clay soils, aged manure, peat moss or sawdust for sandy soils, and coarse sand, pea gravel, compost or well-rotted horse manure with fresh straw for silty soils.
The best time to add your amendments, particularly manures, is in the fall. This allows several months for the properties to incorporate. However, it is still acceptable to do some amending in the spring prior to planting. Your soil test report will have recommendations on how much of any specific amendment is needed.
Where do I start? Choose a site that will give you ample room for plant growth and adequate amounts of sun/shade. Next do a soil test, soil test bags/forms are available at the Butte Conservation District, in Belle Fourche, and the Lawrence Conservation District, in Spearfish. Note that these samples are taken by you and mailed to the soils lab, and in return you will receive a soil test report for a minimal fee. Upon receipt of your soil test report, you will be able to make your recommended amendments in preparation for planting.
Our area has some great resources; don’t be afraid to ask. You can find the Northern Hills Master Gardeners at the Brady Park Farmer’s Market in the summer or online at Northernhillsmastergardeners@yahoo.com or Facebook. Additionally, you can ask SDSU Extension or the Natural Resources Conservation Service about your soils, plants, trees, insects, water, or planting techniques. Happy gardening!
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