At the far left of the INTERPRETATION section are definitions for the “Soil Texture Code”. The code lists the soil types contained in the broad classifications of “Coarse”, “Medium”, “Fine”, "Peat", or (rarely) "Muck". You will refer to the Soil Texture Code when the texture of your soil is shown in the SOIL TEST RESULTS section.
The next three columns in the INTERPRETATION section graphically illustrate the relative levels of organic matter, soluble salts, and pH of your soil, (in this case, along with the Buffer Index). The graphs use stacked letters to form bar charts and they refer to the categories just below them in the SOIL TEST RESULTS section. In the Grapes Report “Organic Matter” has three stacked O’s, which tells you that the amount of organic matter is on the border between low and medium in this soil. “Soluble Salts” were not measured, but there is a stack of two H’s above “pH”, telling you that the soil is moderately acid (low pH). A measurement related to pH is the “Buffer Index”, which has four stacked B’s. Buffer Index is used to calculate the amount of Liming Material needed to raise the soil pH for some crops.
In the Vegetables Report “Organic Matter” has three stacked O’s, which tells you that the amount of organic matter is also on the border between low and medium in this soil. “Soluble Salts” were not measured, but there is a stack of seven H’s above “pH”, telling you that the soil is slightly alkaline (high pH). The “Buffer Index” was not measured for this sample because that test is only run if the pH of a mineral soil is below 6.0.
The rest of the INTERPRETATION section is not separated into columns, but it follows a similar graphical format that illustrates the relative levels (from “very low” to “very high”) of plant nutrients that were measured in these soils. Once again, they refer to the categories just below them in the SOIL TEST RESULTS section. In the Grapes Report, there is a stack of ten P’s above phosphorus (Bray 1 Phosphorus), a stack of seven K’s above Potassium, a stack of three Z’s above Zinc, a stack of ten C’s above Calcium, and a stack of three M’s above Magnesium, indicating that the soil tested in the very high range for phosphorus and calcium, in the medium-high range for potassium, and in the medium-low range for zinc and magnesium.
In the Vegetables Report, phosphorus and potassium were the only nutrients tested. Two different tests were done for phosphorus, Olsen and Bray 1, but only the Olsen Phosphorus test is the relevant one for this soil. (The reason for the two tests and application of the Olsen P measurement will be explained in the next section – SOIL TEST RESULTS.) The stacks of four P’s (above the Olsen Phosphorus box) and five K’s tell you that both phosphorus and potassium were low-to-medium in this soil.
* - Interpretation of the phosphorus level in this example is somewhat complicated because the Vegetable report covers three crops with different phosphorus requirements, and the stack of four P’s refers only to sweet corn. In this example, the phosphorus level is medium-low for corn, but very low for cabbage and tomatoes. The difference between these crops' nutrient requirements is reflected in the fertilizer recommendations.
Soil texture, organic matter, pH, buffer index, P, and K are part of the Regular Series Soil Test, which is the basic and most fundamental package of tests the lab conducts. The nitrate (NO3-N) test is a measurement used to adjust nitrogen fertilizer recommendations for a variety of crops in western Minnesota and is used in some situations in other parts of the state; see Using the Soil Nitrate Test in Minnesota (PDF). Soluble salts and the other nutrients listed on the report are measured only when a deficiency is suspected or is likely to occur. These circumstances include certain soil types and crops which are prone to developing deficiencies of specific nutrients. See the Soluble Salts (PDF), Secondary Macronutrients (PDF), and Micronutrients (PDF) sections in the University of Minnesota Extension bulletin Nutrient Management for Commercial Fruit & Vegetable Crops in Minnesota (PDF) for more information on crops and soils where soil tests beyond the Regular Series are recommended.
Another useful nutrient management tool, especially for perennial fruit crops, is plant tissue analysis. Soil testing and plant tissue analysis complement each other and are most effectively used in combination. For vegetable crops, in-season monitoring of petiole/midrib nitrate-nitrogen can also be useful. Please see "Tissue Nitrate Analysis" by following this link to our companion lab website, the University of Minnesota Research Analytical Laboratory: Plant Analysis.