As the title DIRECT INJECTION VARIABLE RATE APPLICATION, or DIVRA, suggests the system uses a direct injection technique. The site of the injection is in a position that is well downstream in the spray system. It was designed this way to allow the system to better cope with the high groundspeeds and yet maintain rapid response to rate changes.

Due to the low injection rates, the DIVRA system allows us to maintain a near constant volume, which keeps droplet size as close to the optimum size for efficacy. The system will also allow the operator to use their current application equipment, whether that is CP NOZZLES, MICRONAIRS or STANDARD HYDRAULIC NOZZLES along with some additional DIVRA equipment.

The DIVRA system also allows you to apply a primary constant rate application along with the variable application. In past seasons most growers took the opportunity to apply foliar fertilizer generally at 30l/Ha along with a variable application of PIX.

DIVRA Components - The DIVRA system as it stands now consists of 4 components;

1/. A guidance and VRA computer. We are currently using a SATLOC M3 DGPS system that has the ability to use proprietary files to control a variable rate system.

M3 screen shot: When using a satloc M3 the screen can be configured in many ways to accurately monitor the direct injection application. Tank volumes can be entered in the fields on the left hand side. The tank volume then counts down whilst spraying so the pilot knows exactly how much is left in the tank at anytime. The information fields at the top of the screen give you a total of chemical injected for that application and what rate is correctly being applied. In addition, two more fields on the left hand side can be configured to show the target rate for that zone and the actual rate being applied in that particular zone. This makes it easy for the pilot to monitor the application. The tank volume can be reset easily once refilled by hitting the reset button in the variable rate screen.

2/. A pump, flowmeter and control valve to monitor and output the required rates at a suitable pressure.

3/. The DIVRA hopper, boom and loading system. The system uses a variable hopper (DIVRA), which is conveniently placed within the existing hopper. It is usually possible to configure a suitable sized DIVRA hopper so the primary and DIVRA hoppers need reloading at a similar time if running an average DIVRA application volume of 1.5 to 2 l/Ha.

Hopper photo: For the AT-502 the tank is 105 litres in capacity. It is easy to install as it fits onto the internal hopper supports with slight modification to the baffel. Two hoses are connected to the bottom of the tank. One is the suction, the other is the return from the pump. These are connected by camlock fittings at the hopper base for easy connection and disconnection.

4/. A DIVRA boom is needed to get the direct injection site as far downstream in the system as possible. It is essentially a second boom running out with the existing primary spray boom. There is also a three way valve located near the existing loading valve. In one position it is used to load the DIVRA chemical, in the other position it allows the DIVRA chemical to run to the DIVRA pump.