![]() Where nitrate-leaching potential is at a minimum, the amount of residual nitrate in the soil profile before planting has been related to the need for fertilizer N. Nitrogen recommendations are made on the basis of yield goals for a given crop. The Mehlich 3 extractant is being used by many laboratories because it is suitable for measuring soil-test P over a wide range of soil properties and also is a multi-element extractant.īecause nitrogen (N) can be a very mobile element, most laboratories do not routinely run a N soil test. The commonly used soil-test extractants for P in the United States are the Bray-1 (Midwest), Mehlich 1 and 3 extractants (southeastern United States), and the Olsen extractant (calcareous soils). Soil-test levels at which no response is obtained are defined as critical soil-test levels that have been determined by greenhouse and field experiments. Soil tests are widely used to predict the probability of crop responses to application of fertilizers, particularly phosphorus (P), potassium (K), and in some instances manganese (Mn), copper (Cu), zinc (Zn), and iron (Fe) and application of lime. Wolf, Agricultural Analytical Services Labs, The Pennsylvania State University, University Park Thomas Sims, Department of Plant and Soil Sciences, University of Delaware, Newark Raymond Ward, Ward Laboratories, Kearney, Nebraska Ann M. Miller, Department of Soil and Crop Science, Colorado State University, Fort Collins J. Mallarino, Department of Agronomy, Iowa State University, Ames Robert O. Joern, Department of Agronomy, Purdue University, West Lafayette, Indiana Antonio P. Hodges, Department of Soil Science, North Carolina State University, Raleigh Brad C. Fixen, Potash and Phosphate Institute, Brookings, South Dakota Steven C. ![]() Beegle, Department of Agronomy, The Pennsylvania State University, University Park Paul E. Kamprath (Chair), Department of Soil Science, North Carolina State University, Raleigh Douglas B. Relevance of Soil Testing to Agriculture and the EnvironmentĬouncil for Agricultural Science and Technology (CAST)
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