The quality of your soil affects every facet of your landscape, from the plants that will grow to the features that can be constructed. A visual assessment of your soil quality is a good first step in designing or remodeling your landscape. Soil quality assessments study many variables, including soil biota or biology, soil porosity and water‐holding capacity, soil organic‐matter content, and soil chemistry. The assessment can pinpoint further testing needed or determine the steps necessary to improve your soil.
Annual soil assessments are a good way to monitor your landscape management practices to ensure they are actually improving your soil. Follow these steps when assessing soil quality:
- Perform annual assessments at the same time each year to ensure valid comparisons.
- Make all observations under appropriate moisture conditions, when soil is neither too wet nor too dry.
- Assess all soil life, including earthworms, before tilling occurs. Tilling soil can disrupt soil life.
- If you have distinctly different soils on portions of your property, do a separate soil assessment for each of those different soils. You might want to do a separate soil assessment for each bed or planting area.
To assess the soil for a single bed, dig a hole straight down through the soil. Soil depth varies, but dig down at least 6 to 18 inches. It is especially important to dig a deep hole in treeplanting areas to determine the suitability of the soil for trees. Make sure the soil is representative of the whole area you are assessing. If you are not sure the hole you have dug is representative, dig two or more additional holes in the area to ensure you have made a representative assessment of your soil.
An ideal soil has:
- diverse soil biota, with abundant soil organisms including earthworms, insects and other soil life.
- good porosity, with space between the soil crumbles or aggregates that are filled with air and water.
- good permeability, allowing water to infiltrate and move through it.
- good water‐holding capacity, retaining some water in the pore spaces, where it is available to plants.
- good tilth or physical condition, with soil aggregates or crumbles that aid in increasing porosity, permeability and water‐holding capacity.
- good organic matter content, with plant residues decomposing, cycling nutrients back into the soil, and improving the water‐holding capacity and nutrient levels of the soil.
These factors are interrelated. For example, low porosity will result in low permeability, low water‐holding capacity and decreased soil biota, as the living creatures in the soil will have nowhere to live. This, in turn, causes low organicmatter content, further reducing the waterholding and nutrient‐holding capacity of the soil. Identifying problems is the first step to correcting them and improving your soil. This simple assessment exercise will help you evaluate your soil’s quality.
In the table below, circle the appropriate description for each of the indicators listed. Are most answers in the low‐ to medium‐quality range, or in the medium‐ to high‐quality range? What is the overall assessment of your soil quality?
*Rill: Erosion feature caused by water. Rills are not very deep or wide. They can be smoothed away by ordinary farm tillage.
*Gully: Erosion feature caused by water. Gullies are deeper and wider than rills. Gullies are not smoothed away by ordinary farm tillage.
*These signs generally indicate laboratory testing for sodium content should be done. Contact your local Cooperative Extension office for a list of soil testing labs in your area.
(Assessment table adapted from Guidelines for Soil Quality Assessment in Conservation Planning, NRCS Soil Quality Institute.)
What is the overall assessment of soil quality? Make a list of the problems identified by the assessment.
Now that you have assessed your soil, you may have found some problems. The chart on the next page will help you identify potential solutions to your soil quality problems.
Adding organic matter will help remedy most soil quality deficiencies. Be careful not to increase problems when you add organic matter. You can add disease‐free grass clippings and leaves, but most other materials should be composted first, especially manures. Hot composting ensures the organic material is relatively free of diseases (E. coli, viruses), insect pests and their larva, and weed seeds or weed plant parts. Additionally, uncomposted manure is high in salts, which can increase your soil quality problems.