Potato Review

www.potatoreview.com POTATO REVIEW JULY/AUGUST 2021 43 DESICCATION R ICH Daubney, who manages potato crops on mainly grade one silts in South Lincolnshire, North Cambridgeshire and Norfolk, says desiccation has been a key focus for his growers following the demise of diquat. His customers produce packing and chipping quality potatoes including varieties such as Maris Piper, Melody, Agria, Markies and Sagitta. Yields average 45-60t/ha o the eld. Since losing diquat, Rich says he has turned to the stem desiccant Spotlight Plus. “Desiccation quality relies on sunlight so as light intensity decreases over the season, growers need to be more patient with the speed of knockdown,” Rich said. “Spotlight usually takes around seven days after application before activity becomes visual. He says that Spotlight Plus works most e ciently where it is being used in combination with a mechanical ail that has previously removed the leaf vegetation and other detritus, leaving the stem exposed to the full impact of the chemical. A ail and spray programme can be just as e ective at killing o the crop canopy as diquat was before it was banned. “With ail and spray now the preferred desiccation option there are some very important and key factors to consider prior to adopting this technique,” he said. “A ailed crop should be left for 24 hours before applying Spotlight. is gives time for debris to settle and stems to stand more upright after the ail press wheel. Attention should be taken to maintain just enough weight on the ridge to seal cracks, without causing too much ‘Correct flail and spray pivotal to burndown success’ With ail and spray now the preferred option in potato desiccation, Farmacy agronomist Rich Daubney highlights key points that can help growers achieve a cost e ective and timely burn down. disturbance and pressure. is increases the target area of the stem for the desiccant to hit. “Also, ensure that forward speed is not too high, ail blades are sharp and have been set up to a correct stem cut length of about 6-7 inches, ailed debris is directed into the bottom of the rows away from ridge tops.” Where ail and spray is being adopted Rich urges growers to give extra consideration to their crop nutrition strategy, particularly avoiding excess nitrogen inputs and making an appropriate varietal choice. “Excess nitrogen in particular can make skin set markedly more challenging by delaying senescence. is is not easy to predict, especially with the ever more sporadic weather events we now seem to experience,” he said. Skin set is critical so the aim must be to push the crop on to bulk as early as possible using foliar feed where necessary. He advocates ailing a potato crop 24 hours before applying Spotlight Plus at 1l/ha followed potentially by a second application of Spotlight at 0.6l/ha 7-10 days later, especially on indeterminate varieties. “If a crop looks full and lush before the rst desiccant application do not wait too long to see what performance the 1l/ ha rate gives,” Rich said. “Plan to go in again before any regrowth is visible. But, one to two applications of Spotlight is often enough and growers rarely need to use other desiccants such as Gozai, which has a longer harvest interval.” Finally, Rich says that correct nozzle selection can have a signi cant impact on the e ectiveness of the desiccation programme. He prefers to use a nozzle that produces optimum coverage rather than always relying on high water volumes to achieve the necessary crop coverage. “Water volume is not the panacea, it’s more about the nozzle,” he says. “We are aiming for good coverage with higher chemical concentrations within each droplet, and this can often give better results.” “Nozzle technology has come on massively recently, so we are already achieving better coverage than in the past. As a result we rarely need to go in with Gozai after Spotlight – possibly on late crops near the end of September.” “If a crop looks full and lush before the first desiccant application do not wait too long to see what performance the 1l/ha rate gives.” “Water volume is not the panacea, it’s more about the nozzle.”