Specifically, it gives the best possible measure of the level of acidity and a prediction of availability of essential nutrients such as potassium and phosphorus. Equally valuable is the measure of change in fertility level over time by comparing soil test values from the same field year after year. A vital component of high yield production is to maintain a highly productive and fertile soil. A recent summary of soil test results for agronomic crops on a state by state basis indicates that 26 to 75 percent of the soils in the Southeast are inadequate in phosphorus and 23 to 74 percent inadequate in potassium for optimum crop production. The survey evaluated 1.8 million soil samples collected across the U.S. in the fall of 1996 and spring of 1997 and analyzed by private and university labs.
Surveys are no substitute for quality sampling on a site-specific field by field basis.
Yet, this survey clearly reveals that phosphorus and potassium are limiting factors in too many fields and that soil testing is an essential tool for nutrient management planning and the determination of crop fertilizer needs. Some believe that soil testing is utilized more in high management cropping systems, and that the survey values might not adequately measure the sector of untested, low fertility, low-yield fields. Consider the following observations about the southeastern U.S. as they relate to phosphorus and potassium nutrient management for optimum crop production, profitability and protection of the environment. Over one-third of the fields sampled are in need of lime. This practice is essential for optimum nutrient availability and use efficiency by crops.