Method for operating an agricultural sprayer apparatus which has a direct infeed system, comprising the steps: - feeding an active substance into a carrier liquid at at least one infeed point of a line system of the agricultural sprayer apparatus in order to produce, inside the apparatus, a spray liquid to be applied; and - conveying the spray liquid produced in the apparatus to a plurality of application elements (34a-34e) of the agricultural sprayer apparatus, by means of which application elements the spray liquid produced in the apparatus can be applied to an area of agricultural land; a control device of the agricultural sprayer apparatus causing the application elements (34a-34e) to initially be in a closed state at the start of feeding of the active substance into the carrier liquid, at least until the spray liquid produced in the apparatus is in contact with the application elements (34a-34e), and the spray liquid produced in the apparatus being conveyed to the application elements (34a-34e) via at least one application line running between the infeed point and the application elements (34a-34e), carrier liquid being present in the application line at the start of the feeding of the active substance into the carrier liquid, and the carrier liquid present in the application line at the start of the feeding of the active substance into the carrier liquid being at least partially routed back into a storage container for the carrier liquid via a return line, in the process the spray liquid produced in the apparatus being conveyed to the application elements (34a-34e) and at least one of the steps of: - determining the flow rate of liquid through the application line by means of a flow measuring device from the start of the feeding of the active substance into the carrier liquid; and/or - determining the flow rate of liquid through the return line by means of a flow measuring device from the start of the feeding of the active substance into the carrier liquid; the method characterized in that the routing of the carrier liquid, which is present in the application line at the start of the feeding of the active substance into the carrier liquid, back into the storage container for the carrier liquid is interrupted as soon as the determined flow rate of liquid through the application line and/or the return line reaches or exceeds a threshold value. - feeding an active substance into a carrier liquid at at least one infeed point of a line system of the agricultural sprayer apparatus in order to produce, inside the apparatus, a spray liquid to be applied; and - conveying the spray liquid produced in the apparatus to a plurality of application elements (34a-34e) of the agricultural sprayer apparatus, by means of which application elements the spray liquid produced in the apparatus can be applied to an area of agricultural land; a control device of the agricultural sprayer apparatus causing the application elements (34a-34e) to initially be in a closed state at the start of feeding of the active substance into the carrier liquid, at least until the spray liquid produced in the apparatus is in contact with the application elements (34a-34e), and the spray liquid produced in the apparatus being conveyed to the application elements (34a-34e) via at least one application line running between the infeed point and the application elements (34a-34e), carrier liquid being present in the application line at the start of the feeding of the active substance into the carrier liquid, and the carrier liquid present in the application line at the start of the feeding of the active substance into the carrier liquid being at least partially routed back into a storage container for the carrier liquid via a return line, in the process the spray liquid produced in the apparatus being conveyed to the application elements (34a-34e) and at least one of the steps of: - determining the flow rate of liquid through the application line by means of a flow measuring device from the start of the feeding of the active substance into the carrier liquid; and/or - determining the flow rate of liquid through the return line by means of a flow measuring device from the start of the feeding of the active substance into the carrier liquid; - determining the flow rate of liquid through the application line by means of a flow measuring device from the start of the feeding of the active substance into the carrier liquid; and/or - determining the flow rate of liquid through the return line by means of a flow measuring device from the start of the feeding of the active substance into the carrier liquid; the method characterized in that the routing of the carrier liquid, which is present in the application line at the start of the feeding of the active substance into the carrier liquid, back into the storage container for the carrier liquid is interrupted as soon as the determined flow rate of liquid through the application line and/or the return line reaches or exceeds a threshold value.