7/8/2014 ARS Project: Assessment of Soil Analysis Methods (412222) Annual Report
USDA United States Department OF Agriculture
ee | Agricultural Research Service

North Atlantic Soybean Genomics and Improvement

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Research Project: Assessment of Soil Analysis Methods

Project Team
Location: Soybean Genomics and Improvement Bryant, Ray

2008 Annual Report

> Home Project Annual Reports
o FY 2008
» About Us 1a.Objectives (from AD-416)
fr Roscarch | Derive predictive regression equations for nutrient analyses that are
conducted by different laboratory procedures and instrumentation Related National Programs
Programs and Projects through analysis of data collected by the North American Proficiency Ai i
© Subjects of Testing (NAPT) program consisting of 164 soils by 125 analytical o Air Quality (203)
ubjects o} methods tested in average of 165 laboratories in North America. Integrated Farming
Investigation © systems (207)

Pabroducts 5. Gevices 1b.Approach (from AD-416)

> People & Places Recipient will coordinate the project, organize the data, and conduct
statistical analyses of the data using appropriate statistical methods

> News & Events available through existing statistical packages such as SAS. A
minimum of five papers will be developed focusing on: (1) soil pH and

> Partnering EC method comparisons; (2) comparison of soil extractable

phosphorus methods; (3) comparison of soil extractable potassium;
> Careers (4) comparison of soil organic matter methods; (5) an evaluation of

\ laboratory industry performance on primary soil analysis methods;

and (6) comparison of soil extractable nitrogen methods.

3.Progress Report
The objectives of activities conducted under this agreement directly
addresses related in-house CRIS project Objective 4: Determine
precision and accuracy of analytical data among watersheds in support
of the five overall Conservation Effects Assessment Project (CEAP)
objectives (CEAP objective 6, ARS Data Quality Assurance).

This project was established to facilitate access to and analysis of a
large database containing analyses of standard soil samples by
various approved methods by many laboratories. Using these data,
relationships will be developed among different analytical methods for
quantifying soil pH and electrical conductivity (EC), soil extractable
phosphorus, soil organic matter, and soil extractable nitrogen. During
this reporting period, analysis of soil pH data were conducted and a
manuscript entitled "Comparison of soil pH methods on moderately
weathered soils" was developed and submitted for publication in a
peer-reviewed journal. Soil pH is one of the most routine
measurements performed and is used to interpret chemical equilibria
and the rates of many biological processes in soils. Predominantly,
soil pH is measured in soil:water suspensions using a glass H+-
sensing indicator electrode and a reference electrode. Soil:water
suspensions ranging from saturated paste to 1:5 (soil:water) are used
in 26 research and commercial analyses laboratories, Results for
individual soils indicate a non-linear function using matrix EC explains
more than 98% of the variation in soil pH across a range of soil: water
ratios and suspension matrices ranging from 0.00 - 0.01 M CaCi2. It
is our assertion the current practice of determining soil pH in soil-water
suspensions of low ionic strength results in a significant analytical
measurement error associated with liquid junction potentials of a
glass/Calomel H+-electrode system. For soil diagnostic analysis
purposes, we concluded that the measurement of soil pH using 0.01 M
CaCl2 solution at a soil:water ratio of 1:1 is a more robust
measurement for low to moderately weathered soils of North America,
and we suggest that the industry change to pH 1:1 using 0.01M
caci2.

Research conducted under this agreement is monitored by meetings,
site visits, and conference calls between the ADODR and the
cooperator.

This project addresses the NP 207 program vision of “Integrated

agricultural systems that are competitive, profitable, sustainable, and
environmentally compatible”.

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7/8/2014 ARS Project: Assessment of Soil Analysis Methods (412222) Annual Report

Last Modified: 04/25/2009
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