Solutions to lo-till questions

22 September 2001

Solutions to lo-till questions

Three of the main lo-till problems – slugs, weeds and cost control – were tackled at the Lo-Till event seminars. Tom Allen-Stevens listened in

LO-TILL 2001 was a day of solutions, and that was precisely what was served up in the seminar tent. The questions, however, have matured. Growers came looking for answers to specific problems – those management issues that still remain unresolved. The aim of the seminar sessions was to pick on three focused areas and tackle them head on.

The first of these was slugs, and who better to provide the solutions than top UK slug specialist, Professor David Glen, from IACR Long Ashton? "If youre moving away from the plough, you need to be aware of the increased danger of slugs," he told growers.

This is based on evidence from a three-year research study into slug populations. In all three years, slug numbers on the ploughed plots were lowest. In the first year, the direct-drilled plots had the highest number, but by year three the minimum tillage plots had overtaken. "We found significant numbers where the straw had been chopped, which provided them with food and shelter."

A mixture of cultural and chemical methods works best to keep a lid on numbers, he says. The first requirement and the best solution is a well-consolidated seedbed. "Slugs cannot burrow through soil, they rely on cracks and fissures. So where the seeds are closely cased in soil, theyve no idea theyre there."

But he accepts that sometimes it is not possible to get a fine seedbed, in which case he advises growers to drill a little deeper – to about 4cm. "This keeps the seed further out of danger."

This method is best used in conjunction with slug pellets. But Prof Glen advises against drilling deep and putting pellets down the drill, backing this up with more trials results: "You get no difference in slug control if the pellets are drilled, except if they are drilled shallow. The best result was achieved through drilling deep and broadcasting the pellets."

His research has also shown carabid beetles are proving to be a useful predator against slugs; where beetle numbers are high, slug numbers reduce over time. This is where lo-till can help, he says, since the beetles prefer as little soil disturbance as possible.

Growers should use slug traps to monitor numbers, with four slugs over three days as the threshold for treatment. "But the soil surface needs to be moist to bring them to the surface. So if its dry, slug traps can be misleading."

But Colin Stride, from the Soil Management Initiative, took issue with Prof Glen over slug pressure in lo-till situations. "The open, loose, unconsolidated seedbeds typical of plough tillage do not protect the seed from hollowing, nor restrict slug movement, and are very prone to slugs," he says. Even if the surface is made fine and firm, ploughing leaves large gaps beneath this layer, where slugs can move freely.

Fewer numbers

SMI work concludes that where soils are well-consolidated and a stale seedbed is achieved, slugs are fewest in minimum tillage systems. "A glyphosate application 2-3 weeks before drilling kills off green slug food, like rape volunteers."

The stale seedbed is an essential management tool in the war against weeds, according to Masstocks Andrew Richards. "There isnt a great raft of new blackgrass chemistry coming through, so weed management is largely down to cultural control."

In Masstock trials a stale seedbed and later drilling helped achieved 100% control, but it throws up more questions. "If your seedbed is too rough, you still have to break it down before drilling, exposing more weed problems. Too fine and you run the risk of it slumping." The answer is to work the soil early on when its dry and establish the seedbed as soon as the combine leaves the field. "The best system Ive seen is one pass with a shakerator till and Flexicoil. It dealt with a number of issues in one go."

Cue Steve Townsend – a name synonymous with the kit that provides lo-till solutions. The first question he asked growers in a packed seminar tent is whether they knew their operating costs, and if not why they were at the event at all. "If you dont know your operating costs, you wont be able to gauge what the potential savings of lo-till could be."

Once the sums have been done, the key to making cost savings is to simplify your system. "Become an efficient plougher or an efficient min tiller, but dont try to do both. Youll end up with two inefficient systems."

Nor is cutting down tractor hours a saving. "If you keep the same number of tractors, youll only reduce fuel and overtime costs. The maximum saving comes from reducing tractor numbers."

The lo-till tool for the job comes down to either tines or discs, and Mr Townsend urges growers to look in the nettles to see what old kit they can adapt before pulling out the chequebook. A tine enthusiast, he advises growers to be guided by their soil type. Tines work best on light and medium soils while discs can be a better solution on heavier land, he says. "Even heavy land can move to a tine situation after a number of years."

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