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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research » Research » Publications at this Location » Publication #364779

Research Project: Managing Agricultural Systems to Improve Agronomic Productivity, Soil, and Water Quality

Location: National Soil Erosion Research

Title: A critical review on soil chemical processes that control how soil pH affects phosphorus availability to plants

item Penn, Chad
item CAMBERATO, JAMES - Purdue University

Submitted to: Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2019
Publication Date: 6/8/2019
Citation: Penn, C.J., Camberato, J.J. 2019. A critical review on soil chemical processes that control how soil pH affects phosphorus availability to plants. Agriculture. 9(6):120.

Interpretive Summary: There is some confusion in the the peer-review literature with regard to how soil pH impacts soil phosphorus (P) solubility and availability to plants. This is important because solubility and availability directly control the ability of a plant to uptake P; pH management is a critical factor in controlling this. This paper maintains the widely held notion that maximum P solubility occurs at around pH 7, and discounts claims that max solubility occurs at much lower pH levels. There are some occasions where the latter is true, and these exceptions can be real, resulting from complex interactions between different P sorption mechanisms or method of pH adjustment. On the other hand, there can be apparent exceptions, due to methodology employed in the experiment.

Technical Abstract: Occasionally, the classic understanding of the effect of pH on P uptake from soils is questioned through the claim that maximum P uptake occurs at a pH much lower than 6.5-7. The purpose of this paper was to thoroughly examine that claim and provide a critical review on soil processes that control how soil pH affects P solubility and availability. We discuss how individual P retention mechanisms are affected by pH in isolation and when combined in soils, and how both real and apparent exceptions to the classic view can occasionally occur due to dynamics between mechanisms, experimental techniques (equilibration time, method of soluble P extraction and pH adjustment), and plant species that thrive under acidic conditions. While real exceptions to the rule of thumb of maximum P availability at near neutral pH can occur, we conclude that the classic textbook recommendation is generally sound.