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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #361664

Research Project: Sustainable and Resilient Cropping Systems for Midwestern Landscapes

Location: Agroecosystems Management Research

Title: Measuring crop available phosphorus

item Kovar, John
item CANTARELLA, HEITOR - Agronomical Institute Of Campinas (IAC)

Submitted to: Better Crops
Publication Type: Review Article
Publication Acceptance Date: 3/13/2019
Publication Date: 3/21/2019
Citation: Kovar, J.L., Cantarella, H. 2019. Measuring crop available phosphorus. Better Crops. Available:$FILE/BC-2019-1%20p13.pdf.

Interpretive Summary:

Technical Abstract: Proper assessment of plant-available phosphorus (P) in soil is a critical first step to guide the use of P fertilizer in agriculture. Soil P tests provide an index of plant-available P, which is then used to determine the amount of supplemental P, if any, needed to prevent economic loss of crop value. There are different soil tests for P, but the results of soil P tests are typically divided into classes, such as very low, low, medium, high, and very high. These classes are self-explanatory: soils testing low or very low require high inputs of P fertilizer to produce an optimum yield, whereas soils testing high or very high need little or no supplemental P. The amount of P fertilizer to apply also depends on the crop and the expected yields. Applying a fixed amount of P without determining available P with a soil test can result in crop yields below potential or unnecessary fertilizer application, negatively impacting the economic return. In recent years, we have acquired greater knowledge of the soil P cycle, how plants acquire P, and the role P plays in our environment. Therefore, research on improved soil P testing methods and more sophisticated interpretation of the results must continue. End-users, such as farmers, consultants, and Extension personnel, will ultimately benefit from improved measurements of plant-available P.