Effects of extraction time and phosphorus speciation on soil test phosphorus (STP) in Illinois agricultural soils

Miller, Anthony Paul

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https://hdl.handle.net/2142/97288 Copy

Description

Title

Effects of extraction time and phosphorus speciation on soil test phosphorus (STP) in Illinois agricultural soils

Author(s)

Miller, Anthony Paul

Issue Date

2017-03-28

Director of Research (if dissertation) or Advisor (if thesis)

Arai, Yuji

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Soil test phosphorus (STP)
• Bray P-1
• Colorimetric phosphate analysis
• Bray 1
• Mehlich 3
• Mehlich III
• Molybdenum blue

Abstract

Phosphorus (P) loss from agricultural soils is the leading cause of accelerated eutrophication of surface waters. As an essential plant nutrient, however, adequate soil P is required for plant growth. Soil test phosphorus (STP) methods have been developed to correlate P levels in soil to crop growth, so that producers may better estimate the supply of P. There are numerous limitations in STP procedures, however, including: inaccurate estimation of plant available P, (i.e., dissolved reactive P (DRP)), unknown speciation in STP extracts, and the unknown relationship between STP and temporal-scale P release. Assessing these limitations, the appropriate colorimetric methods to distinguish orthophosphate from organic phosphate (Po) in Bray P-1, and Mehlich III extracting solutions were first evaluated, including the effects of acid hydrolysis reactions on Po (phytic acid) and polyphosphate (tripolyphosphate and pyrophosphate) in the STP extracting solutions. Based on the assessment, the effects of extraction time and P speciation on the STP procedures were studied in P rich fertilizer-amended and manure-amended Central Illinois agricultural soils. Although the extent of P release is proportional to the total P extracted by STP methods, the results are highly influenced by longer extraction times and P species. A longer extraction time increases STP values, lowering fertilizer recommendations. Manure-amended soils released more inorganic P (Pi), Po, and colloidal P than did fertilizer-amended soils. The fraction of Po was substantial (10-50% of total P) in STP soil extracts. Overall, the results of this study suggest the complexity of interpreting current STP procedures for fertilizer recommendations.

Graduation Semester

2017-05

Type of Resource

text

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http://hdl.handle.net/2142/97288

Copyright and License Information

Copyright 2017 Anthony Miller

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