Most sportsmen realize that fertilizer is an important component in establishing or maintaining successful food plots. Yet, few understand the importance of lime and soil pH in the food plot equation. In fact, lime is often the most important ingredient for creating and maintaining successful food plots.
Soil "pH" is a measure of the soil’s acidity based on a 0 to 14 scale, with 7 being neutral. Values below 7.0 represent acidic soil, and those above 7.0 indicate basic soil. An important consideration is that soil pH is measured and expressed on a logarithmic scale. In essence, a change in pH of one numeric unit represents a tenfold change in the soils acidity. For example, a pH of 6.0 is 10 times more acidic than a pH of 7.0, and a pH of 5.0 is 100 times more acidic than a pH of 7.0.
Most soils across the whitetails’ range are acidic, and require lime applications to neutralize. Only a few isolated areas, such as portions of Alabama’s Black Belt region and some of the islands in the Mississippi River, have soils naturally above neutral (basic). Acidic soils have several negative effects on food plot crop growth and nutritional value, most notably reduced microbial and insect activity. The survival and proliferation of Rhizobium bacteria, which assist legumes in fixing nitrogen, are limited in acidic soil. In addition, the critical plant growth nutrients of fertilizer - phosphorus, potassium and calcium - "bond" to acidic elements, making them unavailable for plant use. Therefore, if the soil is acidic, only a portion of the fertilizer applied to a food plot will be available to the plants.
There are several reasons why soils are, or become, acidic. Two common causes are related to typical food plot situations. First, the decomposition of leaves and twigs by microorganisms produces organic acids, which in turn make the soil more acidic. Hence, food plots established in forested areas usually have very acidic soils. Second, when forage crops are removed by deer browsing activity, the soil also becomes more acidic. This is especially true of forages grown for deer, since many of the chemical elements in plant matter that help balance the pH are carried off and deposited elsewhere in the form of droppings.
Given that soil acidity levels are so important to establishing or creating a successful food plot, it is necessary to accurately determine the soil’s pH. Most universities with an agricultural school or department provide soil-testing services for a minimal fee ($4.00 to $20.00). Private laboratories specializing in soil testing are also located throughout agricultural regions of the United States. Once the laboratory analyzes your soil, they will provide a recommendation of how many tons per acre of lime that must be applied to neutralize the soil. Usually, one or more tons of lime per acre must be applied to change the soil’s pH. Check with your local cooperative extension agent to obtain a commercial laboratory soil test that can provide landowners with more detailed information about their soil than just pH.