Potato Review

www.potatoreview.com POTATO REVIEW NOVEMBER 2021 57 ROLLER TABLE TREATMENT “Team Sprayers have developed the CTC 2 air treatment canopy for use over roller tables, which applies product to the seed tubers as they move through the spray site via one or two rotating nozzles. It’s been shown to increase coverage by 20-30% when compared to a static nozzle or spinning disc setup, so the investment is a no-brainer,” he said. e CTC 2 system is typically fed by Team Storemaster spray system, which delivers the pressurised spray solution from a 75-litre tank via a 20-litres/min twin diaphragm pump and requires the operator to pre-mix the chemical. Direct injection ere is an increasing trend to add direct injection to the system, which uses low- maintenance peristaltic pumps to deliver neat chemical into pressurised clean water in the spray line with greater accuracy. In addition, up to four chemical hoppers can be utilised, allowing grading line operators to easily switch between products or mix di erent actives without any antagonism in the sprayer tank. “We know that Gavel and Storite Excel (thiabendazole) don’t mix will in the tank and can lead to blocked nozzles, so direct injection reduces that risk. ere is also the added bene t of reduced operator exposure compared with pre-mixing the spray solution,” said Paul. Not every farm will necessarily want to invest in new equipment, but application expert David Turner of Turner Agriculture says there can be simpler ways to improve treatment quality with what you have. He says some set-ups use feed conveyors that are a di erent width to the roller table where the spray site is located and often these systems don’t have variable speed control. Where this is the case, adding a feed conveyor the same width will help deliver a uniform ow of potatoes under the nozzles across the width of the line. “You can also t inverters to enable operators to control the speed of the feed conveyor and roller table and maintain a constant speed of crop ow, whether throughput is 4t/hour or 8t/hour. “If you are relying purely on the weight of the crop, you get more tubers pushed through the middle of the spray site and less on the outside, resulting in under- or over- dosing. For just £200-£300, you can make a big di erence in some cases,” said David. Calibration key With any applicator, calibrating the spray nozzles and pump to the ow rate of tubers through the spray site is essential, ensuring the product is delivered at the correct rate for maximum e cacy. David says the starting point is determining the throughput of the line, which is best done by timing how long it takes to ll a tonne box with seed. Accuracy can be increased by repeating over a few boxes and calculating an average. For throughputs up to and including 8t/ hour, manufacturer Certis recommends a single rotating nozzle under an air treatment canopy for Gavel. For anything above 8t/ hour, a twin nozzle setup should be used. e next step is to calculate the spray output per minute from the output per hour (see panel). In this example, the required output is 266ml/ minute through a single nozzle. Operators should then choose the correct 80deg hollow cone nozzles using a nozzle selection chart and set the appropriate pressure, then run the system up with clean water, catching the output in a measuring jug over one minute. If the output does not match the desired gure, then refer back to the nozzle selection chart and adjust accordingly. e calibration process should be repeated whenever potato throughput changes and as often as practically possible to make sure products are being applied accurately. “Equipment should be NSTS tested every six years as a minimum, but Red Tractor protocols suggest calibration should carried be out between every season,” adds David. HYGIENE TIPS DURING SEED GRADING • Disinfect stores, grading sheds and boxes thoroughly before use • Disinfect grading lines between seed lots where possible • Minimise/remove dust with industrial hoover (no brooms) • Use partitions to minimise movement of dust through buildings • Disinfectant mats can help reduce spread of spores via forklift Correct and regular calibration of seed treatment applicators is crucial in maintaining accuracy and e cacy againts tuber diseases. ➜