Proceedings 2004

Indiana Crop Adviser Conference

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Predictability of Yield Response to P and K Application Based on Soil Test Levels

Probability and Magnitude of Yield Response to P and K Application Based on Critical Soil Fertility Levels vs Yield Goals

Making fertilizer recommendations based on soil test information requires an understanding of how recommendations are developed. The process of taking a soil sample and extracting the nutrient of interest and then interpreting this value to determine the probability of the crop responding to added fertilizer requires extensive field and laboratory studies. Different extractants are used for different soil conditions and thus, require different interpretations. Fertilizer recommendations based on specific laboratory procedures must take into account a variety of factors such as crop to be grown, interpretation of the soil test value, yield goal, soil type, and timing of application. In making fertilizer recommendations for phosphorus and potassium be sure soil test procedures are calibrated for the recommendations being made. Be sure that recommendations have been developed for the soils and region in which you are using them. Finally, don’t underestimate the value of farmer fertility trials in fine tuning fertilizer recommendations to local conditions.

George Van Scoyoc Professor
Purdue Agronomy Dept

Biography:  George E. Van Scoyoc is Professor of Agronomy at Purdue University. He grew up on a farm in Northwestern Ohio and earned B.S. and M.S degrees in Agronomy from Ohio State. He received his Ph.D. degree in Soil Chemistry from Purdue University. He teaches soil science and soil fertility and conducts research in the areas of soil mineralogy and surface chemistry, adsorption of organic compounds by soils and clays, spectral reflectance properties of soils, movement of fertilizers and pesticides in the soil, and soil pH impact on weed growth and soil development.