Digging up the Dirt

My story about soil animals

By Dr Charlie Clutterbuck PhD MSc BSc (Agric) PGCE FRSA

Here, I describe the research I undertook for my PhD many years ago. It was designed to try and find out the effects that herbicides have on the populations of soil animals. In the intervening period, I have come to re-assess its significance. It is all about 'Pesticides' and 'Paradigms'. I want to tell this story to help cast light on the greatest issues of our day - carbon control.

The field of soil ecology was new to me. Having studied agricultural entomology, I was expecting to find lots of insects in the soil to classify. Yet I found that most of the “mesofauna” – those creatures smaller than earthworms, but bigger than bacteria, were not insects.

The early 70’s was strongly influenced by Rachel Carsons’s “Silent Spring”, seen by many as the introduction of the environment movement. Ecologists were haunted by what the pesticides called the “Drins” (Dieldrin/Alrdin etc) had done to kill off birds of prey through the contaminated food chain. At the 1972 UN Conference[1], based in Stockholm because of pollution (acid rain from UK), 26 Principles mentioned (toxic) pollution four times. But no mention of Climate Change or Global Warming.

This was the background to my research project. This story about soil animals, but it also all about ‘Ways of Seeing’ as John Berger once wrote.

Digging up the dirt

I had been working in the root laboratories at East Malling Research Station, where you can still go and see the creatures live and moving in the soil from the vantage of an underground laboratory. But that process distorts the movement of the creatures – favouring those that react to light. It is much more normal to examine soil animals by taking cores of soil and extracting the animals using a variety of ways, the most popular being to shine lights on the overturned soil core to drive the animals down into collection vessels. for more , click to DIY page.

While being more comprehensive in collection of animals, the method suffers from the fact it is a bit like shaking a tree and collecting everything that drops out, then trying to work out how they all fit together. Yet the area of surface in the soil is likely to be 100 - 1000X the area that a similar sized tree above ground would present.

While digging up samples, I wondered what the effects of herbicides – weedkillers. Weedkillers kill weeds. Do they also kill soil animals? I put the idea forward and got funding. Just like that – no business plans, or meetings. It was a good idea, so there were funds. Those were days.

Supervisor

I had a supervisor with whom I I discussed which herbicides I should study. He said: “don’t bother with 245-T, it will be banned by the time you finish”. This was based on what we already knew about the effects it was having on people and soldiers in Vietnam. It was never banned, although later I – along with colleagues in the farmworkers’ union, spent many years trying to get it banned. Eventually the manufacturers withdrew it.

I linked up a lot with my mates in the Soil Zoology Unit at Rothamsted Research Station. Apart from an excuse to go drinking with them on a Friday, it as meant I could discuss what I was doing. I wanted to fit whatever they were doing, taking advise on collection methods and identification etc. Their boss Dr Clive Edwards was particularly helpful.up the research. We determined that what I needed to do was to try and “weed out” whether any effects that were found were “direct” (toxic) effects or “indirect” effects, caused by the 'side effects' like loss of food..

Statistics

To cover myself, I invested a lot in developing my statistics, learning early programming language in order to carry out multiple analyses. I needed them. I counted over half a million creatures in my time, identifying them according to 70-80 species from 10 different herbicide treatments each with their own controls. I counted and classified half a million of the little specks of zoology.As my statistician said: “you are bound to get some significant results with that lot”; one in 20 of all the results are bound to be “significant” as “Significance” is defined as where there is less than a 1:20 chance of it occurring.I spent ages trying to identify possible toxic effects, comparing each herbicide versus another and using the great new invention called the London University mainframe computer been envisaged just a few years earlier. Despite all this, there were few clear effects other than that which would be caused by loss of herbage to eat.But I was always worried that I had missed something and was perhaps looking at the issue too narrowly.I duly finished and presented.

My external examiner was Kenneth Mellanby, famous for his book “Pesticides and Pollution” and head of Monkswood Ecological Research Station. I worried whether he would see the flaw. Luckily he didn’t. He asked me what 'Humus' was, so I was clear on that. The hardest question he asked was “how would you do this differently next time”. So I gave him the answer that he had written in his book. He disagreed. What could I do?.By then I was working for an organisation called British Society for Social Responsibility in Science. (In fact that is how my supervisor introduce me to Kenneth Mellanby, not realising that BSSRS had criticised Mellanby just a few weeks before, because he considered there was no need for nuclear bombs – because chemical and biological warfare were much cleaner..).

Publish

He wanted me to publish quickly, but I was reluctant and eventually didn’t bother. The thesis stood there, with perhaps only 2-3 people reading it.

I have often wondered why Mellanby wanted me to publish so quickly and that it was almost part of the deal for me to get the PhD. And I wondered and thought that perhaps that is the normal thing when you complete your thesis. But I now see that he may also have wanted this sort of research out there to demonstrate that there weren’t (or very few) toxic effects of pesticides. As part of the overall demonstration that pesticides aren’t that bad. Fair enough.

However, I didn’t publish. Perhaps because I had other things to do. But also because I didn’t really think I had anything important to say. To me, showing that any direct toxic effects were pretty mixed and complex, wasn’t something I wanted to say.

But the niggling and doubts persisted, while the years went on. In fact I wrote an article, that was reprinted in the London University’s “Graduate” magazine, exploring the dilemma of what you would do if you knew there was a flaw in your thesis. I said that I could consider the possibility, as my job did not depend on it- but imagine if you had walked into a job on the strength of your thesis.

But there was no (significant!) flaw.. It was over 30 years later that I realised it.

Carbon Loss

The overall trend seems ominous: the loss of carbon from arable land in England & Wales Soil has been significant. In 15 years, soils with the highest concentrations of carbon - greater than 7%, dropped from 22% of soil to 10% of the total. Source Countryside Commission:

In the past few years, as people became concerned about ploughing releasing carbon from the soil, so there has been an increase in 'No-Till' ie 'Don't plough the earth.' Instead weedkillers are often used to keep the crops clean. Yet a recent EU report showed that no-till doesn't necessarily hold more carbon, it merely holds more carbon in the upper soil layers.

I had used grass as the starting point and a total herbicide like Dalapon (and Glyphosate ) to get rid of most of the grass. This is like no-till. But I found that it is the lack of herbage going back into the soil that is the problem. That could be because the grass hadn't grown as much and therefore returned less carbon to the soil.

Glyphosate is now used on fields as 'no-till' to keep weeds - plants, other than the desired crop from growing. So the issue is the lack of weed herbage going back into the soil,I