Speeding up the process for testing manure

“A one-sample analysis can hardly reflect what’s in a manure pit,” said ARS Chemist James Reeves, “because the nitrogen content varies as the dry matter settles out . Reeves, who is developing the protype tester, is at ARS’s Environmental Management and Byproduct Utilization Laboratory at Beltsville, Maryland.

Having access to an accurate, inexpensive manure analyzer will be even more important to farmers if nutrient-management regulations tighten further. With Reeves’s machine, farmers could run the test themselves in a minute or so. The instrument doesn’t require preparation of samples or chemicals to analyze them. The prototype shines invisible near-infrared light through filters onto about 2 tablespoons of manure placed in a small cup. The amount of light reflected back allows a filter spectrometer to measure both the nitrogen and water content. A disk spins so light can shine through any one of 10 different light filters.

“Farmers need to know manure’s water content to calculate how much nitrogen they’re actually applying,” Reeves says. He’s still working on measuring the phosphorus, which is more difficult to do.