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Making the Most of Glyphosate

Original Article published by Farmers Guardian, Arable Features 14 May, 2009

There is much arable farmers across the UK can do to make more from their most widely used agrochemical, reveals the biggest-ever study of glyphosate practice.

Conducted this spring to mark 35 years of commercial Roundup use and undertaken by Monsanto, the study involved more than 1,100 growers in over 60 counties of England, Wales and Scotland responsible for over 350,000 hectares (864,000 acres) of cropping and with in excess of 25,000 years of glyphosate experience between them.

Most have increased their glyphosate use significantly over the past 10 years but even though over 70 per cent of the growers have been using the chemical for 20 years or more, their responses highlight a host of ways in which users could improve their glyphosate efficacy and value, says manufacturer Monsanto.

 “After 35 years some people might think there’s little left to learn about glyphosate,” says study co-ordinator, Susan Mintern. “But our study shows quite the opposite and it really isn’t surprising when you consider how much the agrochemical has changed in its lifetime.

“As far as Roundup is concerned the active ingredient is about the only thing that has remained constant as our scientists have pioneered formulation technologies to meet the changing needs of modern, high intensity crop production.

Much changed

“Compared to the original 360g/litre isopropylamine salt products with ETA adjuvants of the 1970s, for instance, today’s Roundup formulations deliver more than twice the weed-killing power to the roots with far greater consistency.

“They are rainfast in as little as one hour compared to 24 hours. They have up to 60 per cent less weight of product per kg of active. They’re approved for use in cereal and OSR harvest management as well as stubbles, multiple stale seedbeds and post-planting, pre-emergence. They allow cultivation from just six hours as against five days. And they are effective over a wide range of weather conditions, and have broad tank-mixing compatibilities.

“At the same time, the number of different branded and other generic glyphosates on the market has exploded in recent years,” Ms Mintern adds.

“Not only do they come in a range of different salts and active ingredient loadings, they vary widely in their formulations, surfactant types and loadings, and quality – all of which have a direct bearing on their efficacy as well as approvals and usage.

“With glyphosates being so different and capable of being used for so many different jobs utilising them in the most effective way is far less simple than it used to be.”

Underlining the complexity of modern glyphosate use, the Monsanto study reveals most UK growers (83 per cent) currently use the product in at least three of seven or more different applications (Figure 1). Furthermore, nearly a third are using it for five or more separate tasks.

The fact more of those who have been using glyphosate for longer are employing it in most of these applications, and in more applications overall, provides a clear indication of one important way many growers can make more from the agrochemical.

OSR desiccation

“While only around a half of growers with less than 10 years’ glyphosate experience are using the product in cereals harvest management and OSR desiccation, more than three quarters of ‘old hands’ with 30 years or more experience are doing so,” says Ms Mintern. “Clearly a lot of people have a lot to gain from wider pre-harvest use. As they do from using glyphosate more widely in other important applications.”

The study suggests there is still considerable room for improvement in the way most growers use glyphosate.

This potential is demonstrated by the fact 70 per cent of growers don’t always identify weeds before spraying, over half don’t always match dose rates to weed species and growth stage, and just under half don’t always follow product label guidance (Figure 2).
“Thirty five years of experience has taught us the importance of careful weed identification, dose rate matching and spray timing,” says Roundup technical and stewardship manager, Manda Sansom.

“Perennial grass weeds must be treated differently to annuals and mixed populations require a different approach too. Different couch-like perennials also need different treatment strategies.

 “Different rates are, naturally, required for 360g/litre, 450g/litre, 540g/litre and 680g/kg (dry) formulations. Many products aren’t approved for use in many applications, like repeated stale seedbed or stubble spraying, high-rate perennial weed control ahead of sugar beet and potatoes, and post-planting, pre-emergence.

“This puts the onus on following the label and specific off-label approvals carefully; especially so with today’s increasingly tight cross-compliance policing.”

Taking water quality into account in product choice and use is another significant opportunity for improvement identified by the glyphosate study. As is correct adjuvant use.

Only 15 per cent of growers responding to the survey always took account of water quality in their product choice and use, and 10 per cent always used additional adjuvants with Roundup.

“True, this is half the proportion that always do so with other glyphosates, but it’s still unnecessary to enhance activity given the advanced formulation technology already incorporated in our products,” says Ms Sansom.

The survey also reveals many growers are missing out on a major opportunity by failing to employ multiple pre-planting stale seedbeds when conditions allow. “Particularly so in the face of growing post-em grass weed resistance problems. The great value of eliminating an extra flush of annual grass weeds ahead of autumn drilling is well recognised.

“With Roundup products, at least, the label allows this to be done. What’s more, their shorter cultivation intervals (recognised by 75 per cent of growers) means that two stale seedbed cycles are perfectly achievable for most people in most seasons.

“At the same time, just under three quarters of growers see greater label flexibility as an important Roundup advantage. They clearly value its approval for such wide use in so many different applications. But, with only seven per cent always using the same product for all applications, they’re not taking full advantage of the benefit,” adds Ms Sansom.

“Having one glyphosate in your ag-chem store to use across all applications and under all conditions offers a huge opportunity to simplify management. It means you only need to be familiar with a single label, substantially reducing the potential for error and increasing the likelihood of accurate product use. Your product selection, ordering and storage becomes so much easier too.”

It is clear that while UK growers have learned a lot in their 35 years of glyphosate use, there is a lot more most can do to get more out of this key agrochemical.

Essentially, it boils down to understanding that today’s products are very different from those of the past; that all glyphosates are manifestly not the same; and that care and attention are essential in using even the most reliable and highest quality formulations.