Written by Justin Roberts from Agriland
10 years ago, researchers at Harper Adams University in Shropshire in the UK set out on a long-term project to question the effects of machinery traffic and cultivation techniques, such as a plough, on the soil.
A decade later, some concrete results are emerging and these were discussed at a recent conference entitled 'Carbon, Traffic and Tillage' held by the Soil and Water Management Centre, based at the university.
Three different traffic regimes were incorporated into the trial along with three different tillage depths to produce nine plots overall.
The three traffic regimes were tractors with standard tyres, tractors with tyres running at a reduced pressure, and controlled traffic farming (CTF), in which the same field routes are followed every season.
The three tillage depths were to plough, shallow cultivation and zero depth (minimum tillage).
Soil quality was assessed in various ways; these included the soil organic matter, porosity and water penetration properties, biodiversity and worm populations.
The results were set out in detail on the day and it is fair to say that the overall trend was for CTF to come out on top in all categories measured, except for the worm count where it fell behind that of the reduced tyre pressure plots.
High flexion tyres able to run at lower pressures are now available for trailers as well as tractors.
Somewhat surprisingly, given the attention that has been devoted to the relationship between tyres and soil damage, the difference between the two tyre pressures was rarely of any great significance, although running softer tyres tended to have a beneficial effect in all cases.
Unfortunately, what was not clear was the effect of tyre type on the soil as modern high-flexion tyres are designed to provide a larger ground contact area than a simple standard tyre with some air let out.
Quite whether the latest carcass designs produce a more profound effect was not clear, but the message that some benefit was derived from running at lower pressures was certainly apparent.
Earthworm populations was another factor considered and the results were not always what might have been predicted.
The biggest surprise was that the CTF plots came second to reduced tyre pressure when counting the worm population.
These numbers were derived from the abundance of worms in a given area rather than their total mass. Yet, there is so little we know about the subterranean ecosphere and these are only tantalising glimpses of what might be going on.
Interestingly, the method for tempting them to the surface was by the application of a solution of mustard powder which, apparently, acts as an irritant to worms and they head for the surface. All were returned to the soil unharmed.
One result that was expected was that the depth of tillage does significantly affect earthworm numbers, with a negative correlation to greater depth of penetration.
As much as we may pay attention to the various effects on the soil, the most pressing question is the total yield and the following table was presented to show the interaction of the methods for winter wheat over the years.
10 years ago, researchers at Harper Adams University in Shropshire in the UK set out on a long-term project to question the effects of machinery traffic and cultivation techniques, such as a plough, on the soil.
A decade later, some concrete results are emerging and these were discussed at a recent conference entitled 'Carbon, Traffic and Tillage' held by the Soil and Water Management Centre, based at the university.
Plough and other techniques
Three different traffic regimes were incorporated into the trial along with three different tillage depths to produce nine plots overall.
The three traffic regimes were tractors with standard tyres, tractors with tyres running at a reduced pressure, and controlled traffic farming (CTF), in which the same field routes are followed every season.
The three tillage depths were to plough, shallow cultivation and zero depth (minimum tillage).
Soil quality was assessed in various ways; these included the soil organic matter, porosity and water penetration properties, biodiversity and worm populations.
The results were set out in detail on the day and it is fair to say that the overall trend was for CTF to come out on top in all categories measured, except for the worm count where it fell behind that of the reduced tyre pressure plots.
High flexion tyres able to run at lower pressures are now available for trailers as well as tractors.
Somewhat surprisingly, given the attention that has been devoted to the relationship between tyres and soil damage, the difference between the two tyre pressures was rarely of any great significance, although running softer tyres tended to have a beneficial effect in all cases.
Unfortunately, what was not clear was the effect of tyre type on the soil as modern high-flexion tyres are designed to provide a larger ground contact area than a simple standard tyre with some air let out.
Quite whether the latest carcass designs produce a more profound effect was not clear, but the message that some benefit was derived from running at lower pressures was certainly apparent.
A question of bio-activity
Earthworm populations was another factor considered and the results were not always what might have been predicted.
The biggest surprise was that the CTF plots came second to reduced tyre pressure when counting the worm population.
These numbers were derived from the abundance of worms in a given area rather than their total mass. Yet, there is so little we know about the subterranean ecosphere and these are only tantalising glimpses of what might be going on.
Interestingly, the method for tempting them to the surface was by the application of a solution of mustard powder which, apparently, acts as an irritant to worms and they head for the surface. All were returned to the soil unharmed.
One result that was expected was that the depth of tillage does significantly affect earthworm numbers, with a negative correlation to greater depth of penetration.
Yield results
As much as we may pay attention to the various effects on the soil, the most pressing question is the total yield and the following table was presented to show the interaction of the methods for winter wheat over the years.
Standard pressure | Low pressure | CTF |
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