Near-infrared sensing of pig manure nutrients

Over application of nutrients in manure can cause pollution problems. Methods are needed to rapidly determine manure nutrient concentrations, thereby allowing the correct rate of manure to apply to optimize crop production and minimize environmental risk. The objective of this study was to investigate the feasibility of near-infrared (NIR) technology for rapidly analysis of the nutrient contents of pig manure. Diverse pig manures (n = 108) were collected from pig farms in Beijing, P. R. China. Samples were scanned from 833 to 2500 nm in polyethylene bags on a NIR System AVATAR 360N. Moisture, organic matter, total nitrogen, ammonium nitrogen, total phosphorus and total potassium were measured. This study developed calibrations using partial least-squares regression. Outliers resulting from inaccurate conventional analysis or from uncharacteristic scan results were removed from further consideration. Analysis of moisture, organic matter, total nitrogen, ammonium nitrogen, total phosphorus and total potassium in pig manures resulted in r value of 0.9284, 0.9188, 0.9375, 0.9371, 0.8695 and 0.9681, and ratios of range/SEP of 13.04, 12.98, 13.14, 12.75, 11.68 and 17.52 respectively. These ratios (range/SEP > 12) indicated that moisture, organic matter, total nitrogen, ammonium nitrogen and total potassium contents of pig manures had good predictability over a large data range. Total phosphorus had a range/SEP ration of 11.68 indicating that total phosphorus contents of pig manures would be predictable. This study showed that NIR is a potentially usable method for determining pig manure nutrient and moisture content.