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Save our Arable Soils

Erosion

Adam in the BBC radio soap 'The Archers' is worried that soil after their flood is being eroded too easily and reckoning that David Archers’ fields are looking better and wants to know why. It is a good question as we lose over 2 million tonnes of soil a year according to DEFRA Safeguarding our Soils

Erosion is a concern, as spelt out by Krebs introducing the new CCC progress Report. “The Committee’s evaluation of the UK National Adaptation Programme concludes that urgent action is needed with “farming in some of the most productive parts of the country is at risk within a generation, and higher temperatures pose risks to health that are not being properly addressed. Food Erosion is a major threat to food supply within and within a generation unprofitable says Lord Krebbs Chair of Adaption group of CCC. The rate of loss is much the same as it has been for some time – 1-3 cm/year in East England, but the reasons and evidence for erosion need researching according to Cranfield.

Carbon

There was a paper a few years back Nature by P.Bellamy et al, UK soils have lost 12-15% carbon of their total carbon. They used the National Soils Inventory which has been in operation since the early 1960's. the implication was that this may be due to global warming.

But the finding of Bellamy was NOT confirmed by Countryside Survey Executive (Summary & Chap 2). It did not find any decrease in most soil of the ten habitats – like woodland, bracken, fen & pasture. However there were significant losses from arable soils - those growing crops and weeds.

Changes in Soil C density 1994 - 2007
There was one exception of one ‘Broad Habitat(BH). And that was arable land (Crops and weeds). There was a statistically significant decrease over that last ten years, and last 30 years. They clearly did not think global warming was the cause – although it could be an effect. They spelt out their concerns as being to management practices.:
But is it just me, but I didnt know that. Where is the discussion – apart from Adam? Our cropping land has lost 17% of its carbon in last 30 years. That sounds serious to me. This is across 15 million acres – about 1/34 of Britain’s land. So I did the calculations, and if this loss translated to carbon dioxide emissions, then that would represent a contribution of about 1% of UK GWP. (See addenda for calculations)

Soil Animals

And guess where there are the lowest numbers of soil invertebrates? According to Countryside Survey (Chap 8); arable (ie cropped ) land has half the number of soil invertebrates as pasture and about 1/3 – ¼ of woodland soils. Their results were hampered by poor methodology that resulted in a seeming reduction of oribatid mites of nearly 50% in ten years. They have been around for 400 million so it is hard to see how we could have treated soils that badly.

Oribatids are the most important group of animals on the planet – according to E.O Wilson (regarded as one of most significant science commentators and a socio-biologist).In 1 minute Interview by Roger Highfield New Scientist Vol 203 Issue 2722 19 Aug 2009 p23, he said:
“Saving Earth’s biodiversity will take nothing less than an IPCC for species…We are not making the headway we should be in preventing the destruction of ecosystems and species…Most Americans have only the vaguest notion about any of that, even though they can talk intelligently about climate change. Yet when it comes to the living world they are in danger of losing something they scarcely understand. What are they missing? People see nature as trees, plants and vertebrates. Yet the world is run by little creatures most people have not heard of; 99 per cent of Earth’s organisms are extremely small. For example, some of the most abundant and crucial land animals are the tiny oribatid mites, which are the size of a pinhead and look like a cross between a turtle and a spider. They are a linchpin organism of the environment, but 20 years ago when I set out to identify them no one had heard of them. Back then there were just two people in the US able to identify them. Fortunately one agreed to work with me. Yet we still don’t know what the vast majority of oribatids do.”

What is to be done?

We know some will just say ‘organic’s is the answer, but there seems a lot more to it than that. And as Adam is considering there are lots of things which can be done. But who is doing the measuring and working out what is most effective?

NB a lot of research in this area is about the impacts of global warming on our agriculture, not the other way about. So for example the Committee on Climate Change’s Report to Parliament June 2015. ‘Meeting our Carbon Budgets Progress Report 2015 Chap 5 mentions methane and nitrous oxides as contributing to global warming. But it doens mention carbon loss and possible carbon dioxide increase. In fact in the Headline indicator table foe emissions of agriculture, they say CO2‘not applicable’. Nevertheless they say to:

“• Strengthen the current voluntary approach to reduce agricultural emissions: the farming industry should develop robust indicators to properly evaluate the GHG Action Plan. Government should consider stronger measures as part of its 2016 review if it cannot assess the effectiveness of the existing scheme.”

We offer Springtails as our saviour to convey what is going on in soils..

Where has all the carbon gone?

Where has all the carbon gone from the soil?

Likely candidates..
Gulls following plough

1. Ploughing? 
Certainly, whenever you plough, carbon dioxide is released. Details. That is why 'no-tillage' systems are popular in organic systems. A law Environmental Impact Assessment (Agriculture)(England)(2) Regulations 2006 was introduced to control ploughing up pastures. So why has there been a significant decrease in carbon over the last 20 or so years - has there been a concomitant increase in ploughing? Or perhaps there is deeper ploughing?

So I asked some farmworker friends who are out in these fields all day....

“with minimum tillage and strip till the decrease in ploughing has been immense, many farmers have sold their ploughs, those that do still plough only do so rotationally or behind grass.” With blackgrass coming some may move back to ploughing.

“ploughing has probably become less frequent in recent years. We run a plough based system for both cereals and forage maize establishment but many others locally are using either non inversion or direct drilling. Non inversion involves surface cultivation often combined with deeper sub soil loosening. Typically at least 1 pass to create a stale seed bed which is then sprayed to kill volunteers/weeds before drilling. (Glyphosate or other total herbicide?)

Direct drilling typically involves no surface cultivation and seed is planted straight into the previous years stubble. From the technical press it is clear that ploughing is seen as both slower and more expensive by many farmers. The trend towards larger and larger arable units together with a predominance of winter established crops has reduced ploughing, although grass weed pressure and spray resistance has meant that some are returning to ploughing as part of a rotation.

2. Herbicides? 
See Digging up the Dirt'

3. So what is it? With bigger and bigger yields, lots more food taken off the land,

and less left behind? Has anybody measured this?

Adam is planting a herbal ley - to replenish the soil. He is now suggesting lambing at the normal time, so that the ewes and lambs rely on pasture, rather than lambed early and fed on concentrates. It will also mean that lost of the carbon from the grass will go back into the soil. Now Adam has to put his money where his mouth is, and invest in the future project. And now = late 2016. along comes the dastardly Rob who wants to plough up the silly idea.

Hopefully soon, rather than just talking about about worms, he will look at look at all the little creatures – no more than specs, and how they do all the chemical work of keeping roots healthy and breaking down debris. I could almost hear Adam saying ‘we’ll send some clods from each farm to Harper Adams – one of the few HE Farm & food Collleges There they could see whether there is any difference in the little bugs’. And according to the CS they would find arable land has only half numbers of invertebrates as found in pastures, and a third to a quarter of those in woodland.

So who should be doing what?

Clearly Countryside Survey think that management practices need to be changed. But which ? How? How has DEFRA responded?
See News about Environment Audit Committee and Soil Health and this government's response September 2016.

Research

Clearly we need more research - in the following areas

The start would be to do the research, but we are a bit short of publicly funded land research these days, having lost ¾ of our research stations in last 30 years.

Have we invested any research into these areas

1. Where has the carbon gone?

2. Is any emitted as carbon dioxide? If so how much and how.

3. How going to measure carbon dioxide emission from soil

4. What are the changes over last 30 years that have contributed to this decline

5. trying to portion blame? Soil emitting because of ploughing, not holding carbon as with cover crops, more product going off land, less waste coming back to land.

6. Has anybody worked out how much better for the land and emissions animals are compared to vegetable production? The blame usually goes to animals - should it?

Addenda

Method 1

Using figures from above which are in g C kg−1? (carbon grams per kilogram soil)

1. How many arable acres? 15.3 million acres are arable in UK. (Wiki)

2. How much does 8cm topsoil weigh? One AFS (old furrow 6-7 cm deep) weighs 2,000,000 lbs = 980kgm (Answers)

3. How much lost throughout UK?
45.6g/kg (from Table 2 above) X 980 kgm 44688 goes to 38.0 X980 kg 37240 per acre ie loss of 7448 kg times 15 million acres = ca 112,000 million kg (112 million metric tons or tonnes) carbon lost from arable fields in last 30 years

4. Carbon dioxide (given off from soil) weighs 3.6667 times more than the atomic weight of the carbon lost from the soil. Call that 410 million tonnes of carbon dioxide come off arable soil..

5. So over last 30 years, 410/30 = 13.5 m tonnes /yr contribution

6. Current (2008) UK emissions of carbon dioxide are about 530 million tonnes per year (Forest commission) So 13.5 m tonnes /yr is over 2.5% of total…

About 2.25% of all our total GHG emissions.

Method 2

Calculating carbon dioxide emitted from soil as a result of loss of carbon based on 0-15cm figures

1.4.3 Bulk density and soil (0-15cm) carbon stock The mean bulk density of soils (0-15cm) in the Arable and Horticulture Broad Habitat in England in 2007 was 1.25 g/cm3 which when combined with soil (0-15cm) carbon concentration gave a soil (0-15cm) carbon stock estimate of approximately 43tC/ha . This was the lowest carbon stock estimate of all Broad Habitats (See Table 2.9 below)


Using the earlier figures to get percentage fall. This translates to 51.6 in 1979, and would amount

51.6 – 43 t/ha (8.6) difference & 15 million acres (= 6 m hectares)

= 8.6 X 6070000 = 52mt lost

Or 52 X 3.66 carbon dioxide emitted = 191 mt CO2

Results

That second calculation is about half the first estimate. That would be due to the depth of soil – about twice as deep in second calculation; so the weight involved was twice the first. I went for 8cm in first because it was the only depth I could get a weight for and because thought that any carbon loss would be mainly from that top 8cm.


Nevertheless we hear nothing about it. (True? Or am I just missing something?) Where is the discussion when all others are going on about carbon in everything from food to fracking....is it factored in when calculating celery emissions?
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