Cultivation comes under soil husbandry specialist Steve Townsend’s spotlight as he sets out to separate more ‘wheat from the soil management’ chaff in the third of our myth-busting series.
‘Cultivation will give you the soil structure you need’
It also disrupts the natural subsoiling action of previous crop roots that provide preferred pathways for new root penetration and drainage of rainfall. In fact, deep cultivation works against everything that makes the greatest natural contribution to soil structuring – organic matter, earthworms and old root runs, not to mention Father Time. And the sheer amount of weight and horsepower needed doesn’t do most soils any favours either. So, the most sustainable way of improving soil structure is, as I’ve been saying for ages, less not more in the tillage department. We need to allow the sort of carbon-fuelled biology we see under permanent pastures to work its magic; not least letting the glomalin and vast array of other organic compounds produced by soil flora and fauna develop the tilth and stable soil particles we need without continual disruption and disturbance.
Deep cultivation works against everything that makes the greatest natural contribution to soil structuring, says Steve Townsend.
If there’s one thing I’ve learned in my life in farming it’s that cultivations will never improve soil structure. They may help to overcome an immediate problem – like compaction, but they are only ever a short-term fix; and not a very good one, either. We have to understand that cultivations always leave some sort of pan. Either a mechanical pan from smearing or trafficking. Or a sedimentation pan where the act of moving the soil puts the surface crumb beneath lumps from the previous year’s pan. It may not be immediately obvious but it’s always there. And it will always build to bite you back. Yes, subsoiling is sometimes necessary to deal with structural damage – most often from previous soil working under the wrong conditions. But rotational subsoiling as a matter of course – regardless of whether or not it’s needed or where – is a big No-No. Mainly because subsoiling is like heroin to a soil; once you start doing it you need to do it more and more. Civil engineers use deep tines 8
on ground they want to get as hard as possible, knowing that deep loosening is one of the best ways of making soils slump and compact. The poorer the soil the better from their point of view. So it completely defeats me why so many of us who want to achieve exactly the opposite – quite often with some fairly poorly-structured soils – continually turn to metal at depth. Maybe it’s not only our soils that are addicted?
In my experience, shallow top down cultivation is the minimum requirement for building the sort of soil structure we need. And my preference is for cultivating only the relatively small amount of ground around the seed as part of a no-till approach. This gives us the best of all possible worlds. We achieve a nice tilth where the seed really needs it for germination and establishment while maintaining the best, undisturbed soil structure everywhere else. We get rapid and effective root proliferation to depth, just the right conditions for nutrient and water uptake and the least crop vulnerability to drought or flood.
We also get ground with a greater ability to tolerate traffic, fewer weed problems, lower cultivation costs and higher establishment work rates. Of course, this sort of natural structural improvement doesn’t offer the quick fix of sub-soiling. It often takes three or four years of determined action to bring a soil round and overcome the problems created by over-cultivation. Equally, we can’t just move into direct drilling overnight and expect everything to improve. Unless we want to create even more problems for ourselves, that is. Instead, we need to build the resilience of our soils by steadily reducing our tillage, allowing the natural soil structuring processes to reassert themselves from depth. While we are doing this too we need to accept that we’re in a transition that may mean we have to accept some short-term pain for the long-term gain we’re after. Not only this, but we should also reconsider a number of other things we’ve always done – like incorporating straw. Appreciating the complex physical, chemical and biological characteristics of our greatest asset – the soil – and working with it to make the most of them has to be a better way forward than continually trying to rely on cold hard steel and plenty of horsepower. This will never give us the sustainable soil structure we need. Between exploring more of what he sees as today’s most damaging soil management myths with us, Steve Townsend is more than happy to discuss any tillage or soil management issues, interests or concerns with Farmers Guide readers by email on steve. firstname.lastname@example.org
Organic matter As well as hugely damaging to longterm soil structure, deep cultivation, in particular, is the enemy of organic matter. Every time we introduce air into the soil it oxidises carbon from our precious OM bank. The more air we inject the more carbon we lose. So, unless we’re making regular deposits to our most valuable farm bank account, cultivations are just pushing us further into the red. As if that’s not enough, working soil to a depth of more than 4in decimates the deep-burrowing worms that are nature’s ploughmen.
It often takes three or four years of determined action to bring a soil round and overcome the problems created by over-cultivation.
www.farmersguide.co.uk June 2018
1-27 ROP Jun.indd 8
Farmers Guide Magazine June 2018 Issue