Interpretation of Soil Test Results for Grapes

Read the results of the soil pH test. Grapes grow best in soil with a somewhat acidic pH. Most experts recommend a pH below a maximum of 6.5 and place an ideal pH between 5 and 6. If the soil pH is above 6.5, a sulfur soil additive will help to lower the pH. A lime additive will help raise the soil pH if it is too low. Use soil additives carefully in accordance with their manufacturer's instructions because a specific amount is necessary to alter the soil pH a particular level over a certain surface area.

Check the amount of organic matter in the soil on the soil test results. Two to 3 percent of grapes' soil should be organic matter. Add some compost or manure if the soil contains less than 2 percent of organic matter.

Re-test the soil to which you added a sulfur or lime pH supplement or organic materials because those items change soil nutrient levels.

Check the phosphorous level in the soil test results. Experts at the University of Missouri, Mountain Grove, recommend soil with 80 to 100 lbs. of phosphorous per acre for grape plants. Grapes can grow in soil with as little as 40 lbs. of phosphorous per acre, however. Add some phosphorous to the soil if the soil test results show much fewer than 80 lbs. of phosphorous per acre.

Read the potassium level in the soil test results. Soil for grapes should have at least 150 to 250 lbs. of potassium per acre and up to 300 lbs. per acre Add some potassium fertilizer if the soil contains fewer than 150 lbs. of potassium per acre.

Check other nutrient levels in the soil test results. The Ohio State University Extension recommends 200 to 250 lbs. of magnesium per acre, 1 1/2 to 2 lbs. of boron per acre and 8 to 10 lbs. of zinc per acre. Choose fertilizers to adjust the amounts of these nutrients accordingly, and add them to the soil.