Assessing Accuracy of Forage Yield Monitors for Use in Alfalfa.

Whole farm evaluations have shown that accurate yield data for forages grown on farms are most difficult to collect, especially for alfalfa (Medicago sativa L.) and alfalfa/grass fields. In addition, on-farm research, a recommended tool for adaptive management, is hindered by lack of a practical way to collect yield data for farm-scale plots. In recent years, forage yield monitors have become available. Currently the monitors are primarily used for corn (Zea mays L.) silage harvest. The purposes of this project are to (1) evaluate the accuracy of yield and moisture sensing components of forage yield monitors on choppers for the use of alfalfa, and (2) evaluate the potential for their use with on-farm strip trials. Three farms collected calibration and yield data for alfalfa harvest in 2012 and over ten farms participated in 2013. Each farm collected calibration data including the monitor’s calibration factor, percent moisture and percent alfalfa in stand. Samples were collected at the bunk and analyzed for percent moisture to compare to the yield monitor output. Truck weights were used to compare the yield monitor yield value to actual yield on two farms. Preliminary results show percent moisture measured by the yield monitor tended to be higher than lab values by an average of 3.4 percentage points for the first three cuttings. Farm to farm differences in accuracy existed between farms in the study. Differences in dry matter yield between the yield monitor and scale values were 0.30 ton DM/acre and 0.11 ton DM/acre for the two farms who evaluated yield. Additional research is ongoing.