Accuracy of hay moisture sensing systems for round alfalfa bales

Abstract

Moisture measurement is critical when baling alfalfa into round bales for feed. If alfalfa is too wet or too dry, it can greatly diminish the alfalfa crop’s feed quality and cause economic loss to producers. Therefore, monitoring of alfalfa moisture content while baling is critical for producers to maintain hay quality and maximize profits. Currently, there are several different types of moisture sensing technologies available for round balers. But, concerns exist regarding their accuracy and repeatability during hay baling. Therefore, objectives of this project are to 1) Establish a protocol for coring methodology to assess the variation of moisture within a round alfalfa hay bale, and 2) Compare and contrast sensing accuracy and repeatability of different hay moisture sensing technologies. A coring methodology was established to determine the average moisture within a round bale based upon the way a sensor in a round baler chamber would determine the bale moisture; by looking at the moisture contents along the round bale diameter. This method was then compared with the more traditional method of using radial cores only to determine the whole bale moisture content. A sensor testing stand was developed to perform comparative testing between the sensors on the same alfalfa hay bale and collect core samples of material immediately after it was formed. Six commercially available moisture sensors were selected to measure moisture at four pre-determined locations on hay bales. After the sensor measurements, core samples were extracted from the exact same locations to determine actual moisture using oven-drying method. The moisture measurements were conducted during three growth stages and bales were formed with three approximate moisture contents of 10%, 15% and 20%. Six different cuts of alfalfa of the same variety were used to capture all the measurements. A seventh cut was also performed for moisture measurements with the alfalfa baled at 15% and the same growth stage, but different baler compression cylinder pressures (250, 400, and 800psi). Actual moisture content was across different sampling locations were compared to understand moisture distribution and establish coring protocol. Sensor and oven-dried measurements were compared to determine accuracy and repeatability of sensing technologies. Results showed that sensors and oven-dried measurement varied for all the sensors for every growth stage and baling moisture levels, with one sensor exhibiting lowest variability in its readings. The comparison identified the most accurate and reliable sensor among the ones currently available. A second year of testing was also conducted to validate the research from the first year of testing. Future research needs to be conducted to identify correlation between the testing stand readings and actual hay baler moisture sensor readings.