One of my pet peeves is when people refer to soil as “dirt.” Soil is not dirt; it is not some contaminant we should remove. And soil is more than sand, silt and clay particles. Soil is a complex system of chemical and biological interactions that helps produce something we gardeners want – healthy, vibrant plants. Our Nevada soils have several challenges. The cure for many of our soil’s problems is to add organic matter.
Adding organic matter to our soils improves the biological component, providing food for the creatures living there, such as bacteria, insects and earthworms. These creatures are part of an elaborate food web in soil that helps convert chemicals in the soil to a form plants can use as nutrients. This makes our plants more vibrant and our production increases.
Nevada soils are prone to soil texture problems. An ideal soil has 40% sand, 40% silt and 20% clay. Many of us struggle with very sandy or very clayey soil. It is impractical and difficult to change soil texture by adding one of the three components. Trying to add sand to clay soil or clay to sandy soil ends up making a heck of a mess! Clay soils have difficulty draining and are commonly compacted. Sandy soils have difficulty holding water for our plants. Adding organic matter to a clay soil will improve its drainage. Adding organic matter to a sandy soil will improve its water-holding ability.
What organic matter should you use? And when should you add it? Generally, we add compost to our soils. Compost is aged organic matter that has been allowed to decompose to a fairly stable form, called humus. It will hold water and nutrients for plants, improve drainage and provide food for the creatures in your soil. If you want to amend your soil with compost, you can add it anytime, but most people add it in the spring, when they are preparing their soil for new spring plantings.
A word of caution! Our weather is giving all of us garden fever, but don’t work your soil if it is too wet or too dry, as this can destroy soil structure and cause compaction.
If you add uncomposted materials they will degrade in your soil, but the composting process initially uses plant nutrients, so it will rob your soil of the nutrients your plants need. If you choose to add uncomposted organic materials, do it in the fall and bury the material in your planting bed so it can compost in place over the winter. Use caution when adding uncomposted animal manures as they can burn existing plants and may pose a health risk in vegetable beds. Manures need to be completely broken down before planting edibles such as lettuce, chard, spinach or anything else you would eat raw.
Where can you get compost? The easiest way is to make your own. You can buy it from other locations, but use caution. If the material you purchase has not been composted completely, you run the risk of introducing diseases, weeds, and insect pests into your landscape. Well composted organic material should be dark, crumbly and smell earthy, not like decay.
For more information on soils, check out https://www.unce.unr.edu/publications/files/nr/2009/fs0914.pdf
For more information on compost, check out https://www.unce.unr.edu/publications/files/nr/2009/fs0916.pdf
Melody Hefner is the Urban IPM and Pesticide Safety Program Coordinator for the University of Nevada Cooperative Extension. Have a question about your soil or plants? Contact a master gardener at firstname.lastname@example.org.