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The Connecticut Agricultural Experiment Station
Soil pH Experiment
Gregory Bugbee
Department of Environmental Sciences
Michael Cavadini
Department of Analytical Chemistry
Introduction
Soil pH affects the availability of nutrients to plants. pH is a measure of hydrogen ion concentration and ranges from 0 to 14. A pH of 7 is neutral while a pH below 7 is acidic and above 7 is alkaline. The pH scale is logarithmic with each unit 10 times more acidic or alkaline than the next. Most soils in
Connecticut are naturally acidic due to their mineral make-up and the abundant rainfall that leaches out alkaline components. Most plants prefer a soil pH from 6.0 to 7.0. A few plants such as blueberries, mountain laurel and azalea grow best in a more acidic soil with a pH range of 4.5 to 5.0. A variety of kits and devices are available to determine soil pH. These devices usually consist of dyes, paper strips or electronic pH meters. The following experiment uses paper pH indicator strips to determine soil pH.
Materials
· Five one quart zip lock bags
· Five 3 ounce wax paper cups
· Stirrer
· General Range pH Indicator Paper (available from Fisher Scientific or other scientific supply distributor) · Specific Range pH Indicator Paper (available from Fisher Scientific or other scientific supply distributor) · Deionized (DI) Water
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Procedure
Obtain soil from five very different sites. Examples are a lawn, a forest, a garden, a farm, a vacant lot, an abandoned industrial complex etc. From each site use a shovel or trowel to take soil slices six inches deep from several spots. Mix these slices together and place ½ liter of the