An agricultural spreader (1020) is disclosed. The agricultural spreader (1020) comprising: a material holding bin (1024) that holds material to be spread onto an agricultural surface over which the agricultural spreader (1020) travels； at least one delivery conduit (1028-1042) having an inlet end receiving the material to be spread and an outlet end, through which the material to be spread exits and is directed to the agricultural surface through a corresponding first dispersal area； a first radio-frequency (RF) transmitter disposed to generate an RF signal that passes through the first dispersal area, the RF signal bring detectably changed when interacting with the material traveling through the first dispersal area； an RF receiver (1059-1082) disposed to receive the RF signal after the RF signal passes through the first dispersal area, the RF receiver (1059-1082) providing a first output indicative of the received RF signal； and a controller (1122) coupled to the RF receiver (1059-1082) and configured to detect plugging of the at least one delivery conduit (1028-1042) based on the first output of the RF receiver (1059-1082). Furthermore, a method of controlling an agricultural spreader (1020) is disclosed.
