How can rate adjustments be made in direct metering systems?

Rate adjustments in direct metering systems are crucial for ensuring the effective delivery of pesticides in aquatic weed control. The correct approach involves changing the orifice in the suction line. This method allows for precise control of the flow rate of the pesticide solution being drawn into the system.

By changing the orifice size, the operator can alter the resistance within the suction line, which directly influences how much solution is being pulled into the system for application. A larger orifice allows more solution to flow through, increasing the rate, while a smaller orifice restricts flow, decreasing the rate. This method is efficient and ensures that the concentration of the pesticide remains consistent with the desired application rate.

In contrast, while other methods such as changing the spray pattern, altering the nozzle size, or increasing the pump speed can impact the overall effectiveness and application of the pesticide, they do not provide the same level of precise control over the rate at which the solution enters the system as changing the orifice does. These alternatives might be more about the distribution or coverage of the pesticide rather than directly adjusting the flow rate from the supply.