Indicators of phosphorus status in soils: significance and relevance for crop soils in southern Belgium. A review

Abstract

Introduction. Phosphorus (P) is an essential element for plant growth. Therefore, it is essential to accurately evaluate its content in the soil. This requires reliable indicators of soil P status. Literature. This paper reviews literature regarding the indicators of P status in soils. Many indicators can be found, including single extractions (soluble, available, or total P), which are the most common indicators used worldwide. Over time, increasingly complex P indicators have been developed as sequential extractions which characterize the various forms of P, degree of P saturation, diffusive gradients in thin films, biological extractions, isotopic methods, or more complex models. To make a choice among them, different criteria should be applied, including relevance, cost and time, ease of interpretation, and, most importantly, the objective of the analysis. It is also necessary to analyze the appropriateness to soil and climate. Firstly, this paper describes the various types of indicators present in the literature, and proposes a classification system. Secondly, all cited indicators are evaluated and compared. Finally, the P indicators met in Wallonia, southern Belgium are discussed. Conclusions. Each P indicator presents advantages and disadvantages. This review highlights the importance of careful consideration of indicator choice, and the establishment of interpretation thresholds.