Method for optimizing the amount of slurry spread on a soil to be fertilized and corresponding slurry spreading apparatus

An apparatus for spreading slurry on a soil to be fertilised, comprising a vehicle (2), which comprises a slurry spreading device (4), and a pipe system (5), which comprises a conduit (6) connected to the slurry spreading device (4);

• the vehicle (2) and the pipe system (5) being suitable to transfer the slurry to the slurry spreading device (4);
• the vehicle (2) further comprising an analyser device (7) connected to the conduit (6) for acquiring the concentration (Cm) of at least one ingredient of the slurry, a valve (8) arranged in the conduit (6) for regulating the flow rate of slurry fed to the slurry spreader device (4), pressure sensor means (9, 10) for measuring a pressure difference (ΔP) between two points (9a, 10a) of the conduit (6) respectively upstream and downstream of the valve (8), a speed measuring device (11) to measure the speed (V) of the vehicle (2), and a control unit (12) configured to calculate an effective volumetric flow rate (Q) of the slurry as a function of the measured pressure difference (ΔP), to calculate a target volumetric flow rate (Qt) of the slurry as a function of a target spreading factor (Nt) of said at least one ingredient, the concentration (Cm) of said at least one ingredient, the measured speed (V) and a spreading width (W) of the slurry spreading device (4), and to adjust the opening of the valve (8) as a function of the difference between the effective volumetric flow rate (Q) and the target volumetric flow rate (Qt);
• wherein said pipe system (5) comprises a bubble trap device (16) communicating with said conduit (6) at a point upstream of said analyser device (7) for intercepting and eliminating bubbles in the slurry;
• wherein said bubble trap device (16) comprises an expansion chamber (17), which communicates with said conduit (6) and is placed in an elevated position for collecting air bubbles rising from the slurry, a level sensor (18) for detecting when the slurry reaches a maximum level in the expansion chamber (17) and a vent valve (19) for expelling air from the expansion chamber (17) and controlled in closing by the level sensor (18).