Page 164 - Nutrient Management Planning Guide

158

Manure Test Interpretation

Important Terms

Table 4.3.1 Key Terms and Definitions

Term Definition

Crop Available Nutrient Nutrients (e.g., nitrogen (NO

3

-N)) that are in a form that plants can absorb and use. Retained Ammonium-N

The amount of ammonium-N corrected to account for expected N losses that occur during application.

The most reliable source of information regarding manure nutrient content is obtained through laboratory analysis of a representative manure sample. Laboratories

provide a range of manure analyses, but it is important that results be interpreted properly. The remainder of this chapter will focus on interpreting the results of manure analyses to facilitate nutrient management planning.

Book Values and Manure Test Results

Book values for manure nutrient content can be used to verify that manure test results are within expected ranges. If test results appear either low or high in comparison to book values, contact the testing facility to verify that there were no errors made during either analysis or data entry. Alternatively, extreme results may suggest faulty sampling method or inappropriate handling of samples prior to sending for analysis.

All laboratories generate reports that are returned to the person who submitted the manure samples for analysis. Every lab will have their own unique format of how this information is delivered, but all reports should contain the same basic information.

General Information on the Report

The report will identify the person to whom the report is to be sent as well as information that helps identify the sample and type of the manure (#1 and #2 in Figure 4.3.1). When reviewing test reports, verify that the information is accurate and review any comments included on the report (#7).

The report should include dates when the sample was received and processed (#3). Review these handling dates to see if there were any unusual delays in shipping that might affect the accuracy of the results. If not stated on the report, contact the lab to determine whether samples are retained for a period following analysis, in case analysis must be repeated to verify unusual results.

Some reports will also include reference to the procedure or analytical method used for individual nutrients or parameters (#6). If using different labs from year to year, this information can help verify that labs are using the same analytical procedures so that comparisons of nutrient content between years are valid.