There’s no escaping it, slugs are the bane of direct drillers
This month soil husbandry specialist, Steve Townsend of Soil First Farming turns his attention to slug management.There’s no escaping it, slugs are the bane of direct drillers, as they are of anyone with rape in the rotation. Having said that, slug problems certainly aren’t confined to those direct drilling or growing OSR. That much became crystal clear to almost everyone on heavy ground trying to nurse their crops through the ‘perfect slug storm’ of last autumn and winter.
Cultivation is definitely a good way of disturbing and killing slugs. Equally, slug populations are dealt a serious blow by bare, sun-baked ground. So it’s hardly surprising an approach involving the least possible cultivation following the best maintenance of residue cover to preserve soil moisture can increase pressures from this ‘slime-ball’ of a pest.It’s important to appreciate, though, that a well-informed no-till approach involving far more than merely direct drilling can progressively diminish slug problems over the years; by creating firmer soils which reduce the blighters’ mobility and force them to the surface where they’re exposed to predation; by reducing the poorly drained conditions they love; by ensuring more accurate seed placement for the most rapid crop germination and growth away from their attentions; by allowing enough time for effective establishment after their peak of autumn activity and by shifting the emphasis away from the close winter cropping rotations under which they thrive – to name but a few specifics.In the meanwhile, there are a number of cultural ways of minimising slug problems especially valuable in the early years of direct drilling while the benefits of the far firmer, better and more biologically active soil structure it creates build-up.Harrowing OSR stubbles, in particular, with a light cultivator can really help. Moving the crop residue and tickling the soil surface after harvest is a quick, low cost operation. It disrupts slug nests and eggs, drying them out and exposing them to feeding rooks and crows. At the same time it helps improve the effectiveness of the seedbed consolidation that’s vital to protect seeds and germinating seedlings.Local soil consolidation immediately above the seed can be difficult if the slots or slits produced by the direct drill cause bridging of the rear roller. This makes a heavy roll following both wheat drilled after OSR and rape drilling crucial. By which I mean a roller that weighs at least 0.6 tonnes per metre – ideally 0.8t/m, but not more – driven at a steady 4mph to exert its pressure evenly. Light rolls bouncing across the surface at speed are good for nothing but easing apparent workloads!Light cultivation ahead of drilling can, of course, be very useful in stimulating extra grass weed and volunteer OSR germination for more effective pre-planting Roundup (glyphosate) control too. But an exciting new approach – drilling on the green – offering the prospect of minimising slug damage in wheat after rape as well as tackling volunteers could turn current spraying practice on its head.Direct drilling into actively growing OSR volunteers rather than dead or dying residues gives slugs an immediate diet they appear to prefer. So, while they feast on the volunteers, the wheat seed remains free from hollowing to germinate, establish and develop. And by the time the slugs have got through the rape seedlings the wheat is well beyond its most vulnerable stage.Work with companion cropping in OSR is currently investigating the extent to which sowing vetches or buckwheat with the rape seed may give the same ‘alternative diet’ benefits. It’s early days yet, but the indications are most encouraging.Slugs present a clear challenge for many moving to no-till. However, it’s a challenge to which we have a growing number of solutions. To such an extent that the short-term risk is well worth running to secure the major sustainable crop production benefits the regime so clearly offers.Rotation comes under scrutiny in Steve Townsend’s next no-till column. He is more than happy to discuss any tillage or soil management issues, interests or concerns with Farmers Guide readers by e-mail on [email protected] or by phone on 01452 862696.