Soil testing and making fertilizer recommendations are not the same thing. While soil test results estimate the plant available nutrients in a field, the fertilizer recommendation, which is based on an interpretation of soil test results, determines how much lime and fertilizer are needed by a particular crop species on a particular field. Several philosophies are used in interpreting soil test results for lime and fertilizer recommendations. Each of these philosophies is based on different assumptions about crop needs and how crops respond at different soil test levels and different amounts and ratios of nutrients. For any of these philosophies to have value, they must be correlated to the soil types and climatic conditions present.