Does Ploughing Fit In Regenerative Agriculture?

Watching the live feed from NASA last week as the rover ‘Perseverance’ touched down on Mars was a quite spectacular achievement. A planetary alignment, or confluence, of millions of externalities came together to achieve something marvellous, along with a generous helping of rigorous planning and attention to detail.

Sometime a series of events can surprise you in every way. Just recently a series of events unfolded which form the basis of this article. The first instance was when someone posted on TFF a slide from a webinar which appeared to show that ploughing was good for the soil. Intrigued by this I found a recording of the webinar and proceeded to watch with interest. The researcher presenting the webinar made no such claims about ploughing, quite the opposite, it was suggested that to increase SOM we needed to move away from intensive cultivations. As per usual communication was the loser, and I suspect a lot of people went away feeling rosy as they knew that cultivation was again ok.

A few days I was watching another webinar listening to notable practitioner and teacher of ‘Regen Ag’ espouse that ploughing in a regen ag system is ok because every farm and every situation is different. At this point I went and found something better to do than listen to pointless nonsense. I’ll admit that the first pillar of Conservation Agriculture (CA) makes reference to ‘minimal soil disturbance’ and not ‘no soil disturbance’, but does it really allow for maximum disturbance? I know that we all want to be flexible. Flexibility within the confines of the system is allowed, but ploughing is well and truly stepping out of the system, and for what? I would argue there is no gain from rotational ploughing, in fact I would go further and suggest that each rotational ploughing destroys the very biologically active system we are trying to create.

The clock has been reset to zero and you have to start all over again. It should be noted at this point when I refer to ploughing or cultivation I am referring to any intensive cultivation such as subsoiling, ploughing, combined single pass machines with legs and discs, powers-harrows etc.

The final event happened shortly after the aforementioned webinar where I happened to hear James Alexander of Primewest being interviewed on Radio 4’s ‘Farming Today’ programme. James mentioned some research that had been carried out on his farm comparing the net carbon gains of his organic system compared to his Regen Ag system. Knowing James a little I contacted him to find out more about the work undertaken and the results. Upon speaking to James it became clear that the real eureka moment had been completely lost in the short clip played on Farming Today.

Cultivation, as we all know, plays a considerable part in carbon release from the soil. The research, undertaken by Charlotte Cook of Indigro Agronomy, using the Cool Farm Tool to calculate net carbon release and sequestration, revealed exactly what I was anticipating. It is important to note at this point that if you are not practising Conservation, or Regenerative Agriculture then cultivation is an important part of your overall establishment strategy. We are not against cultivation per se but are focused on achieveing the benefits of optimising cultivation inputs.

From the data in table 1 it can be seen that for all metrics, except fuel use, the regen ag system has a higher carbon output than the corresponding organic, in particular the massive spikes from the manufacture and use of nitrogen fertilisers. This does not come as a surprise as I am sure we are all familiar with the large energy demand during manufacture of fertiliser N and resulting carbon–loss from soil once the nitrogen is applied. All of this does not paint Regen Ag in good light until we turn our attention to the broader picture with the inclusion of cover crops into the calculations, shown in table 2.

Here we can see that the action of including cover crops along with reduced soil movement through zero-till has significantly altered the picture. The carbon stock change per hectare now shows a large net sequestration of 8.7 tonnes/ha for the regen-ag system. This is over 3 times the sequestration achieved compared to a production system where intensive cultivation is employed. This tends to agree with some research from the US which showed that soil ploughed to 11 inches released 30 times more CO2 than undisturbed soil in the following 24 hours.

I am not trying to pit organic against conventional production, far from it, but it’s a useful comparison to show that our choices are not always straightforward. It also very much depends upon your viewpoint on the use of pesticides. The most important point of all of this is that we have to learn to reduce our tillage practices as much as possible if we really want to benefit our soils and the wider environment. Similarly we are going to have to become a lot more focused on our use of nitrogen fertilisers.

While we may be able to reduce our dependence on them partially I am not certain we can ever maintain our current level of output without them in some degree. Our use of nitrogen fertiliser is probably on borrowed time, and we really need to focus on how we can use this resource much more efficiently, or at the very least begin to cut N rates back. A production system based around CA principles should allow us to do this, for as we build soil carbon, we are naturally building soil nitrogen. We also need to ‘grow’ more of our own nitrogen through better rotations and better soil health.

 Good soil health can be measured by indicators such as soil bulk density and porosity, water infiltration and air movement, good levels of soil organic matter and biological activity, reduced loss of soil, nitrogen and phosphorus into ground and surface waters. We know intensive tillage negatively affects all of these parameters and every time we plough we effectively reset the clock on achieving the aim of functioning soil. It could also be argued that by doing this you are never going to see the real financial benefits of regen ag and functioning soil biology if you cannot reduce the level of cultivation you employ. So with good planning and attention to detail it is possible to employ a production system which does not rely on the damaging effects of cultivation, and the wider environmental issues that cultivation can create. But ultimately are we happy to allow the promotion of #ploughing in conjunction with #regenag? Or does this detract from the message we are trying to convey?

My warmest thanks must go to James Alexander of Primewest & Charlotte Cook of Indigro for allowing me to use their research. I must also stress that I have used their research to support my own particular viewpoint and may not necessarily be what the authors were intending to show.