Evaluation and Calibration of a Soil Moisture Sensor for Measuring Poultry Manure or Litter Moisture Content

Moisture content (MC) of poultry manure or litter affects its ammonia (NH 3 ) emissions. Relating MC to ammonia emission of manure or litter is thus of importance to modeling and/or managing ammonia emissions from the manure sources. Development of such relationships would require the knowledge of ammonia emission and the concomitant MC of the manure or litter. This work was carried out to characterize the operational performance of a commercially available soil MC sensor for measuring MC of meat-bird (broiler and turkey) litters and laying-hen manure. Laboratory and field calibration tests of the sensor output vs. MC of the source were conducted for the meat-bird litters and layer manure, respectively. Moisture content varied from 27.1% to 55.5 % for the broiler litter, 22.8% to 56.1 % for the turkey litter, and 11.0% to 75.0 % for layer manure. Bulk density (BD) varied from 318 to 468 kg · m -3 for the meat-bird litters. Sensitivity of the sensor to source temperature was also evaluated. Multivariate linear regression models were developed to relate the sensor EMF output to the litter or manure MC and BD (R 2=0.95 – 0.98). The impact of litter temperature on MC measurement by the sensor was found to be rather small, 0.31% of the measured mV per o C deviation from the mean operating temperature over the range of 4 o C to 24 o C. Results of the study indicate that when properly calibrated, the soil MC measurement sensor offers a reasonable means to quantify MC of poultry litter or manure on a real-time basis.