What's Up With Your Soil?

What Is Soil?

If you were to take a large section of your land, your soil would be the topmost layer, the layer you’re most likely grow vegetables in. It can be anywhere from 6 inches to 2 feet deep.

Soil is the unconsolidated upper layer of earth composed of organic matter, rock particles, minerals, clay, gasses, liquids, and organisms that together support life.

The “space” or pores in unconsolidated soil allow water and air to move through the soil, thus providing space for organic materials.

In Utah’s semi-arid/arid climate, our soils rely on irrigation to support the growth of vegetables and fruits.

"It’s the amount of water percolating through that soil that will also create the amount of biomass that grows and then start forming the soil as we know it."

 - Paul Grossl, Utah State University Professor of Soil Sciences

Why Should I Have My Soil Tested?

It’s good to know what’s going on with your soil so you can know what it needs to produce a successful garden with a high yield of fruits and vegetables. But knowing how to read your soil test, and in turn how to treat it, requires a bit of learning and research, which is part of the fun of being a nerdy gardener.

Knowing characteristics typical to soils in Utah’s semi-arid region can help you understand what nutrients you’ll need to add to your soil. For example, because of the abundance of calcium carbonate (the main ingredient in limestone) in the soils along the Wasatch Front, soil pH is in the alkaline pH range from 7.2 to 8.5 and sometimes even higher. In this pH range, micronutrient metals, like iron, zinc, and manganese become less available to plants.

In urban settings, your soil is prone to exposure from the surrounding environment. Even soils that look dark, rich, and moist may still be lacking essential nutrients or contain trace metals like lead that can be harmful, particularly to small children.

How Do I Sample My Soil For Soil Testing?

The following are the steps necessary for the USUAL soil test. You can find out more information on testing and treating your soil on their website. You'll first want to download their Home Soil Test Form, which you'll fill out and send in with your sample.

Depending on the size of your garden, take anywhere between 5 – 20 samples from various spots in your garden.

• Using a shovel dig about 6 - 12 inches deep and place all samples in a bucket or wheelbarrow.
• Mix all the samples in the bucket well, remove any rocks and break apart large chunks.
• Take about 2 measuring cups from the bucket and place in a resealable bag, make sure it’s sealed well!

Which Tests Should I Get And Where Do I Send My Soil Sample?

You’ll first want to fill out this USUAL soil testing form (which also includes thorough instructions on taking your soil samples). As we mentioned, this blog post is tailored to home gardeners in urban and suburban environments.

Paul Grossl, who has done a lot of research on urban soils, recommends a Routine Soil Test and if your living in an urban and/or industrialized area to also have a Total Elemental Composition analysis done to make sure there aren't any trace metals, like lead or arsenic, present in your soil. The Total Elemental Composition is an additional thirty-three dollars. It appears as test S19 on the USUAL price-lists for Soil Tests.

Routine Soil Test

• Provides Phosphorus (P205) and Potassium (K2O) fertilizer recommendations
• Provides Nitrogen (N) fertilizer recommendations tailored to plants the client indicates are to be grown (please provide this information on the submission form)
• Provides soil salinity and pH levels useful in choosing appropriate plants for these important conditions in arid/semi-arid Western US environments
• Provides a soil texture classification used to determine water holding capacity and irrigation regiment. This will tell you how much sand, silt, and clay are present in your soil.

If you've identified your plants (or trees) are experiencing chlorosis, or iron deficiency, you may want to consider the Micro Plus Test.

Micro Plus Test

• Everything in the Routine Soil Test
• Key micronutrient levels that are often deficient in arid/semi-arid Western US soil conditions (Iron, Zinc, Copper, and Manganese)
• Provides recommendations for deficient nutrients tailored to the plants the client indicates are to be grown (please provide this information on the submission form)

Once you've collected your soil samples, have filled out the forms, and selected your tests:

Mail To

USU Analytical Labs
1541 N 800 E
9400 Old Main Hill
Logan, UT 84322-9400

What Do I Do Once I’ve Gotten The Test Results Back?

The USUAL lab will mail you your test results, usually within 5 to 10 working days. The tests will also list some recommendations on what treatments to give your soil, which is helpful information.

There are a variety of ways to treat your soil depending on what it is lacking or has too much of. If your soil needs more nitrogen and less salt you can add blood meal, as one example. For more phosphorus and calcium you can add bone meal. A rich compost can help with soils that are dense or having drainage issues. We recommend doing your research and if you’re still at a loss you can contact the USUAL lab.

Some Issues Typical To Utah Soils Along The Wasatch Front

1)    Alkaline soil pH (pH values above 7)

Because of the abundance of calcium carbonate (the main ingredient in limestone) found in the soils along the Wasatch Front and most agricultural soils in Utah, soil pH values are alkaline ranging from 7.2 to 8.5, and sometimes even higher. In this pH range, micronutrient metals, like iron, zinc, and manganese become less available to plants.

When plants are deficient in these nutrients they suffer in their quality, health, and fruit yield.

2)    Salinity

Soils along the Wasatch Front can also be high in salt. You can have the salinity of your soil tested, which is one of Paul’s recommended tests. There are different ways of treating soils high in salt.

One way is to flush the salts out of the root zone with a clean source of water. This can be done either through flood or sprinkler irrigation.  If your soil seems heavy and compacted, it will have drainage issues (which will also hold the salt in). Adding a rich compost to the top 12 inches of soil will help open up your soil, allowing the salts to drain out.

However, you’ll want to avoid using organic compost from animal byproducts like poultry, cow, or horse manure, as those composts can contain a lot of salt.

3)    Clay

Many garden soils in Utah may contain more than the desired amount of clay (greater than 30% clay). Too much clay holds onto water and causes drainage issues. You can have a texture test done (also one of Paul’s recommended tests), which will tell you how much clay, sand, and silt is present in your soil.

When purchasing topsoil, Paul recommends asking the vendor for topsoil that is less than 30% clay, less than 70% sand, and less than 70% silt.

If your soil tends to be high in clay, adding and mixing in good compost will help, but again, if you’re having salt issues avoid compost derived from animal sources.

For good composting practices check out our video; Composting with Wasatch Community Gardens.

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