Most gardeners understand the importance of adding fertilizer to the vegetable garden. However, the use of lime and the need for proper pH may not be common knowledge.
Vegetable garden soil falls into one of three broad categories: acid, neutral or alkaline.
The pH scale is from zero to 14, with seven defined as neutral. Below seven the soil is acidic and above seven the soil is alkaline. Most gardens have the highest productivity when the soil has a pH of 6.0 to 6.5.
Most soils in Dawson County have a low pH. It is not uncommon for our soil to have a pH of 4.5 to 5.0, if lime has not been added in a number of years.
Poor vegetable performance with low pH is usually caused by aluminum or manganese toxicity. Calcium, magnesium, potassium and phosphorus availability decreases as soil becomes more acidic.
Routine applications of lime will prevent and/or correct low pH. However, it is important to realize you can add too much lime to your garden. Adding too high of a rate of lime could cause the soil pH to be over seven on the pH scale. If the soil is too alkaline, the effects to productivity can be the same as an acid soil.
How does a gardener know if lime is needed, if so, at what rate?
A soil test is the only answer. Testing of soil is a service performed thousands of times weekly at the University of Georgia soil test lab. Testing soil is fast, simple and cost very little ($8, including postage). In most cases, gardeners find testing their soil saves money by using the correct amount of fertilizer.
One of the most important steps in soil testing is collecting the sample. Soil test results are no better than the sample submitted to the laboratory for analysis. A soil sample weighing about one pound represents thousands of pounds of soil in the landscape or garden. Therefore, it is extremely important that samples be properly and carefully taken.
• Take soil from a number of locations in the sampled area and mix them together in a clean bucket.
• For trees and shrubs, take soil from six to eight spots around the dripline of the plants and mix together.
• For lawns and pasture, sample to a depth of four inches. For gardens, ornamentals and fruit trees, sample to a depth of six inches.
• Place sample in clean bag or container and bring to the Dawson County Extension Office. The extension office is located at the Dawson County Agricultural Center, 298 Academy Avenue, Dawsonville (old library).
• Only one pint of soil is needed.
For more information, contact the Dawson County Extension Office at (706) 265-2442.
Clark Beusse is the Dawson County Extension Agent.