Variability of Soil Test Results: Implications for Fertilizer Recommendations.

Many fertilizer recommendations rely on having reliable soil test results. A soil test can vary based on spatial and temporal variability. Historic nutrient application methods and natural soil variation influence spatial variability and the sampling method that should be conducted for most reliable results. Fertilizer banding, broadcast fertilizer overlap and presence of historic features such as homesteads, pastures, manure application and field merging should be considered. Some soil nutrients, particularly K, vary due to soil moisture and season of sampling. Soil sampling should be conducted with consideration of probable spatial variability, as well as with consideration of previous soil sampling history. Soil sampling, if conducted with due regard for history and natural variability can continue to be a useful tool for directing nutrient application.