By Richard Tharp, Wildlife Biologist
Wildlife food plots, also known as “green fields,” are highly popular among white-tailed deer hunters and enthusiasts. Planting some type of food source for wildlife has increasingly become big business since the 1970s. Establishing and maintaining wildlife food plots is one management strategy used by landowners and sportsmen to provide wildlife with one component of their needs. Annually in Alabama, hundreds of thousands, if not millions, of dollars are spent on seed and fertilizer to produce these wildlife food plots.
For landowners and managers who desire to maximize the productivity of their green fields, soil testing and addressing pH should be an integral part of their food plot program. Soil testing is simply gathering samples of soil from the openings and having it analyzed. The results from soil testing are a recommendation for amounts of nitrogen (N), phosphorus (P), and potassium (K) needed per acre. Also included will be how much lime is needed to raise the pH level of the soil. The pH value is a numerical figure indicating the soil acidity or alkalinity (base). Soil pH is measured on a scale ranging from zero to 14, with seven being neutral. These figures are a representation of the number of hydrogen ions in the soil. Levels below seven indicate acidic soils and those above seven are basic soils. The pH scale is logarithmic changing tenfold for each number change. For example, a soil with a pH of 4.5 is 10 more times acidic than a soil with a pH of 5.5.
Maintaining soil pH at the appropriate level is critical as it can limit plant growth by restricting nutrient availability. Consequently, low soil pH can be a limiting factor in producing quality wildlife openings. In acidic soils, nutrients are bound to soil particles. Therefore, limited amounts of the applied fertilizer will be available to the plant. When soil pH is extremely acidic (4.5 pH), a high percentage (70 percent plus) of nutrients from applied fertilizer is unavailable. At a pH of 6.5, which is considered medium acidic, almost 20 percent of nutrients are tied up in the soil. Additionally, activity of microorganisms is reduced, limiting nitrogen fixing in leguminous plants. These conditions can be corrected by applying lime to the soil, which will raise the pH level. In turn, nutrient availability for plants is improved and activity of microorganisms is increased enabling legumes to fix nitrogen.
Lime comes in many forms. Two common liming materials are calcic limestone, which is ground limestone, and Dolomitic limestone, which is also ground limestone but high in magnesium. How quickly lime can affect soil depends on the particulate size of the lime, type of soil, lime to soil contact and moisture content of the soil. Lime should be applied several months in advance of planting to realize the full effect. Remember, liming is often more important than fertilizing.
Without exception, fertilizer and money is wasted when soil pH is too low. The maintenance of wildlife openings is expensive and labor intensive. Therefore, maximizing productivity is very important. A properly maintained wildlife opening is an asset to hunters and hunting clubs.