An agricultural field sprayer used for the spreading of liquids, in particular, of liquid carrier liquids and/or of active agent concentrates, such as fertilisers, plant protection agents, or the like, which are dissolved in carrier liquids, - with at least one distributor boom with spreading nozzles disposed thereon and/or assigned thereto, said spreading nozzles being used for the spraying and/or fine distribution of the liquid to be spread, wherein the spreading nozzles are fluidically connected to and/or supplied by at least one outlet line; - and with at least one loop line, which is at least in some sections guided along the distributor boom, wherein at least one power-source-driven pump (32; 38) for the conveyance of various carrier liquids and/or of active agents is assigned to the outlet line and/or to the loop line; - and with at least one mixing chamber in communication with the loop line and forming a circulation system together with the loop line, said mixing chamber being used for the storing and/or mixing of carrier liquids and/or active agent concentrates to be supplied from or being supplied from the loop line, wherein the mixing chamber has at least one supply device configured as an adjustable metering device assigned to it, said supply device being used for the adjustable supply of active agent concentrate to the mixing chamber, wherein at least one control valve is disposed between the outlet line and the loop line, said control valve being used for the metered supply to the outlet line and/or to the spreading nozzles of the carrier liquid being conveyed in the loop line and of the active agent or active agent concentrate being conveyed in the loop line, and wherein the field sprayer is configured to convey the active agent produced in the at least one mixing chamber on a permanent basis via the loop line along the distributor boom or, as applicable, parallel to the outlet line, characterised in that a measuring device is disposed in each case between the outlet line and the at least one control valve and/or between the loop line and the at least one control valve. - with at least one distributor boom with spreading nozzles disposed thereon and/or assigned thereto, said spreading nozzles being used for the spraying and/or fine distribution of the liquid to be spread, wherein the spreading nozzles are fluidically connected to and/or supplied by at least one outlet line; - and with at least one loop line, which is at least in some sections guided along the distributor boom, wherein at least one power-source-driven pump (32; 38) for the conveyance of various carrier liquids and/or of active agents is assigned to the outlet line and/or to the loop line; - and with at least one mixing chamber in communication with the loop line and forming a circulation system together with the loop line, said mixing chamber being used for the storing and/or mixing of carrier liquids and/or active agent concentrates to be supplied from or being supplied from the loop line, wherein the mixing chamber has at least one supply device configured as an adjustable metering device assigned to it, said supply device being used for the adjustable supply of active agent concentrate to the mixing chamber, wherein at least one control valve is disposed between the outlet line and the loop line, said control valve being used for the metered supply to the outlet line and/or to the spreading nozzles of the carrier liquid being conveyed in the loop line and of the active agent or active agent concentrate being conveyed in the loop line, and wherein the field sprayer is configured to convey the active agent produced in the at least one mixing chamber on a permanent basis via the loop line along the distributor boom or, as applicable, parallel to the outlet line, characterised in that a measuring device is disposed in each case between the outlet line and the at least one control valve and/or between the loop line and the at least one control valve.