Location: Poultry ResearchTitle: Using electrical resistance probes for moisture determination in switchgrass windrows Author
Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 7/25/2011
Publication Date: 8/10/2011
Citation: Chesser, G.D., Davis, J.D., Purswell, J.L., Rowe, D., Lemus, R. 2011. Using electrical resistance probes for moisture determination in switchgrass windrows. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). ASABE #1111253. Interpretive Summary: Moisture content is a primary measurement of interest in harvesting, processing, and storing energy crop biomass. Electrical resistance meters for use in traditional forage harvesting operations are designed for leafy grasses such as alfalfa, rather than switchgrass, and accuracy has not been characterized in biomass harvesting applications. Two electrical resistance meters were evaluated for accuracy over a range of moisture contents and packing pressures by comparison against standard oven methods. Results indicated that factory calibrations did not accurately report switchgrass moisture contents. Meter accuracy generally increased with pressures up to 95 lbs per square foot.
Technical Abstract: Determining moisture levels in windrowed biomass is important for both forage producers and researchers. Energy crops such as switchgrass have been troublesome when using the standard methods set for electrical resistance meters. The objectives of this study were to i) develop the methodologies needed to measure MC in switchgrass using electrical resistance meters, ii) to determine the effects of pressure and probe orientation on MC measurement and iii) to generate MC calibration equations for electrical resistance meters using switchgrass in the senescence growth stage. Two meters (Meter 1, Farmex HT-PRO; Meter 2, Delmhorst F-2000) were selected based on commercial availability. A forage compression apparatus was designed and constructed with on-farm materials and methods to provide a simple system of applying pressure achievable by any forage producer or researcher in the field. Two trials were performed to test four levels of moisture contents (10, 20, 30, and 40%), five pressures (0, 1.68, 3.11, 4.55, 6.22 kN/m2; 0, 35, 65, 95, 130 lb/ft2), and two probe orientations (axial and transverse) in a 4x5x2 factorial design. Results indicated that meter accuracy increased as pressure increased. Regression models accounted for 91% and 81% of the variation for Meter 1 and Meter 2 at a pressure of 4.55 kN/m2 (95 lb/ft2) and a transverse probe orientation. Calibration equations were developed for both meters to improve moisture measurement accuracy for farmers and researchers in the field.