University of Maryland Extension

Problematic Results and Flawed Analyses

Introduction: 

Results occasionally come back on soil and manure/compost analyses that are confusing or potentially flawed. The following examples, explanations, and resolutions should help provide guidance in some of the more common situations that arise. 

Examples and Resolutions:

The following table describes examples of problematic and flawed analyses and how to proceed:

Problem

Example(s)

Explanation

Resolution

Compost analysis with an ammonium-N value of <0.01%

 

Mushroom Compost Example

The value <0.01% means the ammonium-N is below the detectable limit of the equipment/ method that was used for analysis.

This value should be entered as “0” in NuMan and any calculations that are required.

Manure analysis with P2O5% listed as “< 10.0”

Waypoint Phosphate Example

The lab did not do the conversion from P to P2O5 on their output

If P concentration was provided on the upper part of the report (as in this example), then a nutrient management planner multiplies the P concentration by 2.29 to obtain the phosphate content and annotates the analysis


If both P and phosphate were zero or “<” values, contact the lab and request that they consult the raw data for the sample.

Soil analysis from 3rd party

(e.g. fertilizer company)

Willard Output Example

Soil test outputs from 3rd parties may not be used to develop a nutrient management plan because:

1) Maryland Department of Agriculture requires that the actual soil test report be included in each nutrient management plan.

2) The nutrient management planner may have no information about the type of extract used for the soil analysis and cannot make a correct choice of soil test labs in NuMan.

The company should be able to obtain a copy of the output from the soil testing lab to provide to the operator and/or nutrient management advisor upon request in order to develop the nutrient management plan.

Manure or compost analysis with % ammonium-N that is greater than or equal to the total N

A&L/Southern States Example

Waters Example

Rising Sun Mushroom Compost Example

The ammonium-N is just one form of N included in the total N; therefore ammonium-N cannot be higher than the total N. In an organic fertilizer source, there would be some organic N composition, so similarly the ammonium-N cannot be equal to the total N (as seen in the mushroom compost example).

In this case, the operator or consultant should contact the lab because there has been an error.

 

Note:  There is a liquid fertilizer called aqua ammonia, a solution of ammonia in water, wherein all the nitrogen is actually in the ammonium form.

Compost or manure analysis submitted as a soil analysis

A&L Example

Organic fertilizers such as manure and compost used a nutrient sources should not be submitted to a lab as soil samples because the analysis is inadequate for a nutrient management planner's needs for plan development. A nutrient management planner needs the following information on organic materials used as nutrient sources: total nitrogen, ammonium nitrogen, phosphate, potash and moisture

The operator must submit another sample on a manure submittal form.

 

 

Unusually high organic matter in a soil analysis (approaching 10%)

A&L Example

In some cases, urban growers and other operations growing produce for fresh market are using composted material as their growing medium (≥50% organic matter), rather than natural soil.

Because of the high organic matter content, composted materials used as a growing media should be submitted as a growing media or potting media analysis. The methods typically used to measure soil organic matter on a soil analysis cap out well before 50% (often less than 10%).

 

Confirm growing conditions and sampling techniques with the operator to discern if this is the issue.

Results from a lab not listed in NuMan Pro software

Pedogenesis Example

Soil test results from some labs cannot be converted to the Maryland Fertility Index Value (FIV) scale if they were not part of the initial study or if they have unusual extraction methods.

Contact one of the Nutrient Management Specialists to determine if the test results can be converted.

Waypoint or Agri Analysis in Leola, PA: Which lab to select in NuMan

Waypoint PA-Agri Analysis Output

Waypoint PA-Waypoint Output

Since Waypoint bought Agri Analysis in Leola, PA, clients receive multiple outputs: one that looks like the Agri Analysis output and one that looks like the output from Waypoint’s other locations. 

If the output is in the Agri Analysis format (see example), select "Agri Analysis"

If the output is in the standard Waypoint format (see example), select "Waypoint Mehlich" as the lab in NuMan.

Soil test units for phosphorus presented as “P-FIV” on soil test report rather than P expressed as ppm

Spectrum ppm format

Spectrum FIV-P format

Spectrum provides this output as a service to clients who may be interested in viewing the P in this format.

NuMan converts all the nutrients based on the conversions appropriate for that lab. 

 

In NuMan 4.2 this may be done by inputting the FIV-P in the white input column in the NuMan file, then back down the value until the converted FIV-P in the yellow column matches the soil-test-reported FIV.  

 

In NuMan 5.0, a conversion has been added that takes the P-FIV at face value and converts the other nutrients.  Choose Spectrum, ppm, FIV-P.

 

Also make note of the P-ppm values on the original soil test so any reviewer understands this process.

Contact:

Contact the University of Maryland Agricultural Nutrient Management Program if you need further clarification, or if an issue comes up that is not represented here, by emailing your problematic analysis and question to one of the Nutrient Management Specialists (College Park Staff & Nutrient Management Specialists).

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