Soil Quality in Vegetable and Small Fruit Production

Bulletin 898

Evaluating Soil Quality

Methods and Tools to Evaluate Soil Quality

Ohio Soil Health Card and USDA Soil Quality Test Kit

Soil Probe

Proper evaluations of soil quality require methods to measure indicators and a baseline or standard set of optimum values for comparison. Reliable methods and standard values are available for some properties. Soil chemical properties can be routinely and reliably measured. For example, soil fertility analysis measures certain chemical properties of soil and is widely used in modern agriculture. Decades of research on the responses of different crops to varying pH and nutrient levels on a range of soil types assists growers in knowing how much lime and fertilizer (synthetic or organic) is required to achieve high marketable yield. Soil sampling for fertility analysis is relatively simple for farmers or consultants to do, and many soil testing labs provide accurate and inexpensive lime and fertilizer recommendations.

Physical and biological properties are more difficult or expensive to measure objectively and interpret. Still, there are two tools available to assist farmers in assessing soil quality at the farm or field level—the Ohio Soil Health Card and the USDA Soil Quality Test Kit.

The Ohio Soil Health Card and the USDA Soil Quality Test Kit are

USDA Soil Quality Test Kit Photo courtesy GEMPLER'S, Inc.

useful in assessing soil quality at the farm or field level. The Ohio Soil Health Card evaluates a soil's health or quality using soil and plant indicators identified by farmers. Twelve specific indicators are grouped into four categories—soil tilth, soil life, soil air and water, and plant vigor, which are subjectively rated on a scale of Good, Fair, or Poor. The Card relies heavily on crop growth as an indicator of soil quality, even though it is an indirect indicator. In this way, the Card integrates physical, chemical, and biological aspects of soil quality.

The Card was developed for farmers by farmers and is a tool to help monitor and improve soil quality based on farmers' field experience and working knowledge of their soils. Regular use allows farmers to record long-term trends and changes in soil quality and to compare the effects of different soil management practices. Because it provides a qualitative assessment of soil quality, the Card is most effective when filled out consistently over time by the same person for each individual field.

The USDA Soil Quality Test Kit is a toolbox with components for taking relatively simple and inexpensive measurements of soil-quality indicators while in the field. In fact, several of the measurements can only be done on intact soil in the field. The test kit was developed by the Agricultural Research Service, refined and expanded by the NRCS Soil Quality Institute, and designed for ease of use by farmers, consultants, Extension and NRCS staff, and other agricultural professionals. Soil properties measured with the Test Kit include:

• Physical indicators—water infiltration, bulk density, water-holding capacity, aggregate stability, soil slaking, and penetration resistance.
• Biological indicators—soil respiration and earthworm numbers.
• Chemical indicators—pH, electrical conductivity (soluble salts), and nitrate-nitrogen.

The Soil Quality Test Kit Guide carries instructions describing how to complete the tests, worksheets for recording data and calculating results, and suggestions on how to interpret the results of each test. Test kits are available for use in Ohio through Ohio State University Extension District Offices and the organization Innovative Farmers of Ohio (IFO).

If you could have only one tool to evaluate soil quality, the best choice would be to select a shovel and dig a hole.

Soil quality is evaluated to assess the extent of soil degradation and maintain or improve the condition of a soil. In agriculture, soil-quality assessment is only meaningful when the results are used to maintain and improve soil quality. In addition to becoming familiar with how to define and evaluate soil quality, farmers and others will benefit by recognizing the common causes for declines in soil quality. This is important in managing soil quality.