At the far left of the RESULTS section is a box labeled “Sample/Field Number,” which contains the identifying name or number you assigned to the sample when you sent it to the laboratory. There is no identifier for the Grapes Report, and it is "1" on the Vegetables Report. (The grape grower probably sent in only one sample and didn’t bother to give his field an identifier.) If you send in more than one sample, it is critically important that you keep a list of the sample identifiers you assigned to each field or location.
To the right of Sample/Field Number is “Estimated Soil Texture”. Texture is determined by an experienced lab technician on the basis of how a moist soil sample feels when it is manipulated between the thumb and fingers. In the Grapes Report, soil texture is classified as Medium and if you go up to the Soil Texture Code box in the INTERPRETATION section you will see this means that your soil is a loam or silt loam. The “Estimated Soil Texture” is also Medium for the Vegetables Report.
The rest of the categories in the RESULTS section are the numerical results of laboratory analyses that were performed on your soil sample. For the Grapes Report “Organic Matter” is 3.0%, “pH” is 5.5, “Buffer Index” is 6.5, “Bray 1 Phosphorus” is 45 ppm (parts per million), “Potassium” is 110 ppm, “Zinc” is 0.5 ppm, “Calcium” is 1500 ppm, and “Magnesium” is 70 ppm. For the Vegetables Report “Organic Matter” is 3.0%, “pH” is 6.0, “Bray 1 Phosphorus” is 4 ppm, “Olsen Phosphorus” is 6 ppm, and “Potassium” is 75 ppm. If you want to know more about the laboratory procedures used to obtain these measurements, see Our Methods on the University of Minnesota Soil Testing Laboratory web site.
The numerical laboratory results in a soil test report are generally not useful to clients by themselves. That is why the INTERPRETATION section comes first. Laboratory measurements of plant-available nutrients are indices of relative availability, rather than measurements of absolute content, and those indices are expressed on varying scales. The INTERPRETATION section tells you whether the laboratory result is low, medium, or high in terms of the need for fertilizer application. If the soil test is low for a given nutrient, it means that the crop is likely to respond favorably to the addition of fertilizer. If the soil test is high, it means that additional fertilizer is less likely to improve crop growth.
Soil organic matter content is one of the main factors determining nitrogen fertilizer recommendations. The higher the organic matter content, the lower the nitrogen fertilizer recommendation. This is because decomposition of organic matter and the associated release of plant-available nitrogen is a significant source of this nutrient for plants. For examples of the effect soil organic matter can have on nitrogen recommendations, you can see tables for several crops in the University of Minnesota Extension bulletin Nutrient Management for Commercial Fruit & Vegetable Crops in Minnesota. (PDF)
A soil measurement that may be confusing to people is the Buffer Index. Buffer Index is used to determine how much lime is required when soil pH is too low for optimal plant growth. The Buffer Index is only run if the pH of a mineral soil is below 6.0. The box will be blank if the soil is organic or if the pH is 6.0 or higher. Soils differ in their buffering capacity, or ability to resist a change in pH, so soils with the same pH may require different amounts of lime to achieve a similar pH change. The pH measurement tells you whether you need to apply lime, and the Buffer Index is used to calculate how much lime will be required to affect the desired pH adjustment.
Clients often wonder why there are two boxes for phosphorus: “Olsen Phosphorus” and “Bray 1 Phosphorus”. The Grapes Report only has a result in the Bray 1 P box, but the Vegetables Report has values for both Olsen P and Bray 1 P. As noted above in the INTERPRETATION OF SOIL TEST RESULTS section, the Olsen P measurement is the meaningful one for the Vegetables Report. The reason for the difference in the two reports is that different laboratory methods are used depending on the pH of the soil. For calcareous soils with a pH greater than 7.4, the Olsen test is used. If soil pH is 7.4 or less, the Bray 1 test is used. The pH of the soil in the Vegetables Report is 7.6, so Olsen P is the appropriate measurement.
When the Olsen P test is run, there will be results shown in both the Olsen P and Bray 1 P boxes. This is because the Bray 1 test is run on every Soil Test sample, while the Olsen test is only run on samples with a pH above 7.4. If there are numbers in both the Bray 1 and Olsen boxes, the Olsen P value is always the one used for interpretation and recommendations. These two measurements also provide an example of different laboratory methods giving results on different scales: For many vegetables an Olsen P result of 28 ppm is high, but a Bray 1 P result of 28 ppm is medium.