On-farm quick tests for estimating nitrogen in dairy manure

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• On-farm manure nutrient analysis can significantly improve nutrient management strategies.
• Rapid analysis methods are crucial for timely decision-making in agricultural practices.

Purpose of the Study:

• To evaluate the accuracy of six rapid manure testing methods for estimating total nitrogen (N) and ammonium-nitrogen (NH4+-N).
• To compare the performance of different quick tests against traditional laboratory analyses.

Main Methods:

• Collected 107 manure samples from dairy farms across five northeastern states.
• Analyzed samples for total N and NH4+-N using laboratory methods and six quick tests (hydrometer, electrical conductivity meter and pen, reflectometer, Agros N Meter, Quantofix-N-Volumeter).
• Regressed quick test results against laboratory values, analyzing performance based on dry matter (DM) content.

Main Results:

• The hydrometer showed poor accuracy for estimating total N.
• Quantofix-N-Volumeter, Agros N Meter, reflectometer, and electrical conductivity meter and pen demonstrated varying degrees of accuracy for NH4+-N estimation.
• Accuracy of NH4+-N estimation was generally higher for low DM (< or =12%) manure samples compared to high DM (>12%) samples.
• Agros N Meter, reflectometer, and conductivity meter and pen performed poorly with high DM samples.

Conclusions:

• Several quick tests, particularly the Quantofix-N-Volumeter and Agros N Meter, are viable for measuring NH4+-N in dairy manure (slurries and solids).
• Dry matter content significantly influences the accuracy of these rapid tests.
• Further refinement may be needed for high DM manure applications.