Posted by: timchamen | November 10, 2011

Is there a viable alternative to controlled traffic farming (CTF) to protect our soils?

Over the past 80 or more years, the pressures applied to subsoils (0.4 m depth) by machinery has increased by a factor of about 15. While some subsoils have already experienced this pressure through glaciation in the ice age or high pressure tyres working in the bottom of furrows, many have never experienced pressures of this magnitude. What happens to them? Logically, the porosity (air space) gradually gets squashed out of them with the result that roots can no longer find as much air and there is less space for water. Trials prior to 1994 conducted in seven countries, including ones with deep freezing of soils each winter, showed that several passes of wheels on one occasion at the surface with loads of just 5 t was enough to permanently depress yields by 2.5%. We now have loads of 12 t under a single harvester wheel! Are we getting a similar effect and would we actually notice this drop in yield in the short term? Improvements in varieties and better chemical agronomy might mask it, but we are almost losing out on yield potential.
Some might argue that we can go to low ground pressure, but two problems become apparent. First, unless we put all very heavy vehicles on rubber tracks, getting low enough pressures with tyres is impractical – they would be too wide and too costly. Secondly, the unfortunate fact is that it is load not pressure that determines the depth to which compaction travels in the soil. Repetitive loading also builds up compaction – you only have to look at the ruts formed on motorways, or even those on your driveway where your relatively light car runs! OK, I know what you are going to say now, “what about the controlled traffic wheel tracks, aren’t they going to get rutted?” The answer is yes, of course they will, but we need to manage them, either by infilling or a combination of infilling and light cultivation. This is no reason to throw out the system, it’s up to us to design and implement the correct management strategy for permanent wheel tracks, taking account of soils, traffic and moisture regimes.
So, can anyone think of a better way than CTF for managing soil compaction? It’s not perfect and we don’t have the right machinery yet to make it easy, but doesn’t putting all your compaction in as small an area as possible make sense? At least we know where it is and if desperate, can repair it without massive cost.
Your thoughts and ideas would be much appreciated in what I’m sure will be an ongoing debate.

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Responses

  1. Looking forward to some comments

  2. So was I Peter, but seems that either very few have read the blog or no-one has come up with any better ideas! I’ll push for some comments in the new year.


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