Non‐destructive detection of moisture content in Orchardgrass (Dactylis glomerate L.) silage in wrapped round bales using microstrip transmission line sensor and its transmitted microwaves

This paper demonstrates a non‐destructive method for measuring the moisture content of silage in wrapped round bales (WRBs) via microwave signals using a microstrip transmission line (MSTL) sensor and vector network analyzer under outdoor conditions. We analyzed the relationships between the amplitude changes (Δα) and phase shifts (Δφ) of the microwave‐transmitted signals from the WRB surfaces without tearing their films. The press MSTL method was strongly suggested over the touch MSTL method for the non‐destructive measurement of WRB qualities. We also obtained strongly negative and significant correlations between the slopes of the linear regression lines (Δφ–Δα ratios) and moisture contents for frequencies in the range of 3.6–6.2 GHz. Thus, in this frequency zone, the press MSTL method can be effectively used to determine the moisture content of silage in WRBs.