Potato Review

44 POTATO REVIEW JULY/AUGUST 2021 DESICCATION F OLLOWING their rst full season of diquat free desiccation, and potentially armed with greater knowledge gleaned from “real” non-trial conditions without a diquat safety net, many potato growers should now have an even better understanding of what it takes to achieve good desiccation, according to agronomists. Formerly with the Scottish Agricultural College, John Sarup set up SPUD Agronomy in 2012. He and business partner Rob Blades cover 4,500ha of potatoes, mainly across the Northern counties and Scottish borders where John advises on seed, ware and processing crops. “I began looking at diquat free desiccation strategies around 10 years ago when I set up the company, long before diquat’s withdrawal. Early results from ailing followed by the application of a protoporphyrinogen oxidase inhibitor (PPO) were variable, mainly due to a lack of understanding on how PPOs worked back then coupled with a trial and Fine tuning strategies Two advisors share their views on how to achieve successful crop desiccation, where six key areas now need to be addressed. error approach to discovering the key factors that in uence crop senescence,” he said. “Once we’d worked out how to maximise the e cacy of the PPOs by applying them in bright sunny conditions and target them correctly at the severed stems rather than the foliage then results improved signi cantly.” Fast forward to 2021 and John now feels that the vast majority of critical factors that can either make or break desiccation have been fully identi ed and it is now more a case of ne tuning the information already out there to ensure successful crop burn-down. “During the last 10 years, combining knowledge gained from my own work with other trial observations, I’ve identi ed six key areas that can make a signi cant di erence to desiccation outcomes. e rst of these six areas is temperature and timing of the PPO application to maximise its e cacy. Always apply PPOs early to mid- morning in bright, sunny conditions giving the chemical maximum time to kill cells. “ e second key is soil moisture at the time you begin desiccation. is is also important as it will a ect the speed of skin-set. If you can nd a dry weather window and begin the process with a dry soil then you’ll achieve quicker skin- set, critical for crops going into store. “ e third key is better early season planning, not only to reduce the early season weed burden, but also focusing on eld layouts to ensure the ail can turn without damaging headlands – or, even planting a di erent variety on the headlands that you can then harvest as green-top will help to make the later desiccation process easier. John Sarup in field