Spraying system for agricultural machinery, comprising a spraying boom and a liquid circuit itself comprising: - a first main tank configured to contain a treatment liquid, - a first pumping assembly comprising a first pump comprising an inlet and an outlet , the first pump being designed to suck up liquid through said inlet and to discharge the sucked up liquid through said outlet , - at least one first suction line (15a-15c) connected, downstream, to the inlet of the first pump , the or one of the first suction lines (15a-15c), called first main tank suction line, connecting the first main tank to the inlet of the first pump , - at least one first discharge line (16a-16d) connected, upstream, to the outlet of the first pump , the or one at least of the first discharge lines (16a-16d), called spraying line, comprising spraying nozzles mounted on the spraying boom and designed to spray liquid onto plants to treat, - a second main tank configured to contain a treatment liquid, - a transfer line connecting the first main tank and the second main tank with one another and comprising a pumping mechanism designed to suck up treatment liquid coming from the second main tank and to discharge the sucked up treatment liquid to the first main tank , the transfer line further comprises a first valve installed downstream of the pumping mechanism and designed to: - in a first position, place in communication the pumping mechanism with the first main tank , so as to supply the first pump and the spraying line(s) with treatment liquid coming from the first and second main tanks , via the first main tank , and the spraying system being characterized in that : - in a second position, the valve is adapted to place in communication the pumping mechanism with the inlet of the first pump , while bypassing the first main tank , so as to supply selectively the first pump and the line(s) for spraying treatment liquid coming from the first main tank or treatment liquid coming from the second main tank . - a first main tank configured to contain a treatment liquid, - a first pumping assembly comprising a first pump comprising an inlet and an outlet , the first pump being designed to suck up liquid through said inlet and to discharge the sucked up liquid through said outlet , - at least one first suction line (15a-15c) connected, downstream, to the inlet of the first pump , the or one of the first suction lines (15a-15c), called first main tank suction line, connecting the first main tank to the inlet of the first pump , - at least one first discharge line (16a-16d) connected, upstream, to the outlet of the first pump , the or one at least of the first discharge lines (16a-16d), called spraying line, comprising spraying nozzles mounted on the spraying boom and designed to spray liquid onto plants to treat, - a second main tank configured to contain a treatment liquid, - a transfer line connecting the first main tank and the second main tank with one another and comprising a pumping mechanism designed to suck up treatment liquid coming from the second main tank and to discharge the sucked up treatment liquid to the first main tank , - in a first position, place in communication the pumping mechanism with the first main tank , so as to supply the first pump and the spraying line(s) with treatment liquid coming from the first and second main tanks , via the first main tank , and the spraying system being characterized in that : - in a second position, the valve is adapted to place in communication the pumping mechanism with the inlet of the first pump , while bypassing the first main tank , so as to supply selectively the first pump and the line(s) for spraying treatment liquid coming from the first main tank or treatment liquid coming from the second main tank . <EOS>