Do Grape Plants Need Acidic Soil?

Soil Acidity

• Although specific preferences vary by cultivar, most grape varieties thrive in soils with pH levels between 5.0 and 6.0, according to the Ohio State University Extension. However, some varieties, such as American bunch grapes, prefer slightly lower soil acidity. According to Clemson Cooperative Extension, American bunch grape varieties prefer soils with a pH between 5.8 and 6.5. For best results, always research the specific variety, and visit your local nursery to discuss the soil in your area.

Amending Your Soil

• Alkaline soils need to be amended before they can support a grape planting. Elemental sulfur is commonly used to make soils more acidic. Other common soil amendments include iron sulfate, aluminum sulfate and acid sphagnum peat. However, as noted by the Colorado State University Extension, it will not lower pH if your soil contains a significant amount of free lime. To test for free lime content, put a heaping tablespoon of dry soil into a container, then add enough vinegar to moisten the soil. If the vinegar starts to bubble, your soil contains free lime, and these products may not be effective.

Problems

• Soil pH impacts nutrient availability, and improper pH levels may cause nutrient deficiency or toxicity in grape plants. According to the University of Idaho College of Agriculture, iron chlorosis is a common nutrient deficiency that tends to develop in grapes that are planted in soils with pH levels above 8.0. Manganese, copper and zinc levels also decrease in alkaline soils, whereas other nutrients, like calcium, magnesium, sulfur and phosphorus may be present at nearly toxic levels.

Other Considerations

• Combine proper pH levels with other cultural practices for optimal growing success. Grape plants need well-drained soil sites that receive plenty of sunlight. According to North Carolina State University Extension, planting on a gentle slope is ideal, since it aids in air circulation. Grapes should be planted in late winter or early spring. In addition to amending soil acidity, you should also build your trellis and spade or till the soil well before you plant your grape cultivars.