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Title:Effects of extraction time and phosphorus speciation on soil test phosphorus (STP) in Illinois agricultural soils
Author(s):Miller, Anthony Paul
Advisor(s):Arai, Yuji
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Soil Test Phosphorus
STP
Bray P-1, Bray 1, Mehlich 3, Mehlich III, molybdenum blue
colorimetric phosphate analysis
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.
Issue Date:2017-03-28
Type:Thesis
URI:http://hdl.handle.net/2142/97288
Rights Information:Copyright 2017 Anthony Miller
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05


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