Do you have fields that have excessive phosphorus levels? The way we are handling it has changed! Any time a field has a Phosphorus Fertility Index Value (FIV) of 150 or greater, a study needs to be completed to determine the feasibility of additional applications of phosphorus. In recent years the tool used has been the Phosphorus Site Index (PSI), but we now have a new tool – the Phosphorus Management Tool (PMT). In order to complete the PMT study, additional information about the soil is required – the Degree of Phosphorus Saturation, or DPS. Temporarily, we are permitted to estimate the DPS; however, in the future DPS analysis results will be required for fields with excessive phosphorus.
How do you get a DPS result? Soil testing labs can test for DPS. Alternatively, if the lab tests for aluminum (Al) and iron (Fe) using Mehlich-3 extraction method, DPS can be calculated using NuManPro 4.0, the software we use to write your nutrient management plan. Here is what to expect from each of our recommended soil testing labs.
Labs that do not charge extra for the DPS:
• AgroLab Inc.: The “University of D P Sat Ratio” is the same as DPS and is part of their standard soil test.
• Brookside Laboratories, Inc.: Al and Fe are routinely reported for option SOO1. NuMan Pro 4.0 can calculate DPS from this information.
• Spetrum Analysis, Inc.: Will report DPS for UM-PMT when ordering S1 or S2 option.
• University of Delaware Soil Testing Program: The “Percent P Saturation” is the same as DPS and is included in B1 Routine Analysis.
Labs that charge separately for the DPS:
• A&L Eastern Agricultural Lab, Richmond: Al and Fe can be requested for an additional $3 per sample. NuMan Pro 4.0 can calculate DPS when soil test includes Mehlich-3 Fe and Al.
• Agri-Analysis, Inc.: Al and Fe can be requested for an additional $3 per sample. NuMan Pro 4.0 can calculate DPS when soil test includes Mehlich-3 Fe and Al.
• Pennsylvania Agricultural Analytical Services Penn State University: Al and Fe can be requested for an additional $6 per sample. NuMan Pro 4.0 can calculate DPS when soil test includes Mehlich-3 Fe and Al.
Labs with special consideration:
• Water Agricultural: Maryland samples should now be sent to Waters-Kentucky. Why? They use Mehlich-3 as an extractant. Fe and Al can be obtained when one requests the Basic Test 4 + AL. Write “M3 and nutrient management” on soil submission form.
As a special note, some labs automatically run a full range of nutrient testing and keep the information electronically. If the owner of the soil later request additional information, the lab may have it and can provide the information for an additional fee. These labs can retroactively provide the DPS or Fe and Al. Agri Analysis, Penn State, and A&L fall into this category. Waters, however, does not routinely analyze for Al and only keeps soil samples for one month.
The information included in this article is from the new “Comparison of Soil Test Labs” Fact Sheet.