Soil Testing
What’s the difference between soil and dirt? Dirt is what you find under your fingernails. Soil is what you find under your feet. Think of soil as a thin living skin that covers the land. It goes down into the ground just a short way.
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Soil Testing, Do it now for best results!
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| Standard Test: $40.00 Organic Matter (%) Potassium (ppm) Calcium (ppm) SMP Buffer pH Base Saturation Magnesium (%) Sodium (%) Cation Exchange Capacity (CEC) |
Diagnostic Test: $50.00 |
pH Requirements of Common Vegetables
pH (potential of Hydrogen) is the degree of acidity or alkalinity of a substance. The neutral point, where a solution would be neither acid nor alkaline is pH 7.0. Increasing alkalinity is expressed in a number greater than 7.0 and the increasing acidity is expressed in a number less than 7.0. Maximum acidity is pH 0 and maximum alkalinity is pH 14.
Because each unit on the pH scale represents a logarithm, there is a tenfold difference between each unit. As an example, pH 5 is ten times as acid as pH 6, and pH 4 is 100 times as acidic as pH 6.
Controlling the pH of soil is the most common challenge to western Oregon farmers and gardeners. The pH of soil can change from year to year depending upon the amount of rain that we get in a winter. Our soils are usually quite acidic until amended. pH is also one of the soil conditions that can be most easily amended, usually by adding lime products to neutralize some of the acidity. The best time to add lime to the soil is in the winter, since lime is soluble and slow acting in adjusting soil. Garden and agriculture product suppliers can assist the gardener or small farmer with selecting the best amendments after they know the pH and other nutrient requirements for your soil. Most plants in our area will tolerate soil pH in the range of 6.0 to 7.0, but prefer pH in more narrow ranges. The following list will help you decide what pH condition is best for growing your favorite crops:
VEGETABLE FAMILY OPTIMUM SOIL pH
Beans (snap & shell) 6.4
Beans (lima) 6.2
Beets 6.5-8.0
Cabbage family (except Cauliflower) 6.0-7.5
Carrots 6.0-6.5
Cauliflower 6.5-7.0
Corn 5.5-6.8
Cucumbers, Melons & Squash (do poorly in acid soils) 7.0
Lettuce 5.8-7.0
Onions, Garlic, Leeks, etc. 6.0-6.8
Peas 5.5-6.8
Peppers 5.5-7.0
Potatoes 5.5-7.0
Radishes 6.0-6.5
Spinach 6.0-6.5
Tomatoes 6.0-6.5
Source: Garden Secrets, Dorothy Hinshaw Patent & Diane E. Bilderback, Rodale Press, 1982
