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An old doomsday theory in agriculture is back on TV.

According to a report broadcast on France 2 on 31 January 2016 entitled "Les soigneurs de terre" (1), which highlights the theories of Claude Bourguignon, a former agronomist at INRA, the soils cultivated in France will soon be unable to feed us. In this report, we are promised a catastrophic future. In temperate zones, the harmful consequences of ploughing would be progressive and would even go unnoticed. Yet, for several years, conventional agricultural production has been optimal. So how do we explain this impending disaster?

Crops are boosted by mineral fertilisers and tillage, giving the impression of improved fertilisation, but in reality the results obtained are deceptive, as the soil is impoverished due to the depletion of humus. Farmers and consumers alike are being lied to. Today's agriculture is destroying the earth. It serves to fatten a system at the expense of life. Conventional agriculture consists of keeping plants alive in dead soil which, without pesticides and fertilisers, are doomed to disappear. Agricultural soils are being depleted by the spread of intensive farming and the last good soils are being depleted. Analyses of certain soils have shown that their fertility is comparable to that of the Sahara. France is in danger of being covered with infertile fields in the next quarter of a century.

Tillage is also used by home gardeners with a rotovator or spade, and they sometimes use mineral fertilisers. It can therefore be concluded that these amateur gardeners are also responsible for the degradation of the cultivated soil. Have they really noticed it? Is this apocalyptic vision realistic?

If a ploughed soil is really dead and unable to perform its biological functions, this can easily be demonstrated by a simple experiment with 3 jars, soil samples and pearl urea used as fertiliser in agriculture. This experiment is described at the end of this article.

Organic carbon content in France by canton

Variation in organic carbon content between the periods 1995-1999 and 2000-2004 by canton

Sir Albert HOWARD estimated almost a century ago that soils are being depleted and this speech is therefore taken up 80 years later by all those who are convinced that modern agriculture is destroying the planet. In the end, there is nothing new except the repetition of an old theory.

With regard to the consequences of tillage, what about carbon losses in cultivated soils in France?

Between the periods 1995-1999 and 2000-2004, the organic carbon content of soils decreased in 21.4% of the cantons in metropolitan France, which are mainly intensive farming areas where cereal monocultures predominate (particularly the Paris basin and northern France). On the other hand, the organic carbon content of soils is stable or increasing in 48% of cantons (including 10% increase) (2) . The situation in France is therefore not so dramatic, even if it is necessary to review certain agricultural practices in intensive crop areas.

Crops in stony or desert areas that produce humus

When agricultural practices are well conducted, including synthetic fertilisers and even ploughing, there is no shortage of examples that demonstrate that soil can be enriched with humus even when its original structure is deplorable:

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In the Asse valley in the Alpes de Haute-Provence department, cereals are grown on poor soils saturated with gravel and pebbles as shown in the photo on the left.

Field in the Asse valley with crop residues

Field filled with stones - Asse valley (Alpes de Haute-Provence). Crop residues can be seen after harvesting.

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In the region of El Oued in Algeria, plants are grown in the desert in circular fields. The wilaya of El Oued is at the top of the list of wilayas in southern Algeria in terms of agricultural crops, particularly early crops, dates, cereals, potatoes, peanuts and market gardening. Successions of wheat and potato crops are accompanied by an increase in soil carbon content (largely provided by the stubble left behind after the wheat crop) (3).

If you fly over the Arabian desert, you will see that it is also dotted with huge circular fields covered with wheat.

There are few more infertile regions than these arid deserts of Africa. Yet farmers are able to grow cereals and vegetables. How can soil saturated with stones or sand become rich in humus when mineral fertilisers are applied? Simply by the decomposition of organic matter from roots and rootlets, and by the development of microbial biomass as a result of exudates synthesised by plants to feed the rhizosphere (see description of the mechanism here). The rest is provided by crop waste. After a harvest, anyone can easily see with a fork spade that a cultivated soil has been enriched with organic matter from the roots, which persists for a few weeks to a few months in the soil (depending on the nature of the crop) before being decomposed by the microflora. It is also noted that earthworms thrive at a depth of 20 to 30 cm, feeding on crop residues even if the soil has been worked and has received synthetic fertilisers. The population of earthworms is all the more important when plant cover is applied interculturally or when the soil has received manure and/or compost.

The wriggling of an earthworm that excites a minister

In the France 2 report of 31 January 2016, a farmer in the Sarthe region who has converted to no-till organic farming shows a clod of earth taken from a field covered with cover crops. In this lump of earth, a worm is wriggling around, which Stéphane Le Foll, former Minister of Agriculture, Agri-Food and Forestry, hastens to pick up. Such a demonstration can also be carried out on land that is properly cultivated using traditional methods, especially when there is sufficient humidity and there are no heat waves (which force the earthworms to burrow into the soil to protect themselves from the heat). Gardeners and market gardeners who have never noticed that their cultivated plots are turning into a desert must have had a good laugh watching this TV programme. It is mainly aimed at the majority of French people who live in big cities and have no experience in agriculture, and at the few followers of the various chapels of non-scientific agroecology ready to swallow anything.

In the France 2 report, we learn that in a cultivation system characterised by the use of plant cover and the absence of tillage, it takes a minimum of 5 years to restructure a soil and 10 to 15 years to recover acceptable yields. But there are other methods that are just as effective and much quicker, such as spreading composts made from crop and livestock farm waste, shredding straw on site, burying intercropping plant cover.... It is still necessary to correctly estimate the real loss of humus every year, which depends on several factors such as climate, soil structure, the method and frequency of tillage, the existence of irrigation in summer, the type of crop and how rotations are carried out....

A very simple experiment to check whether a frequently ploughed soil that has received synthetic fertilizers is dead.

This test consists of checking whether the microflora of a soil that has been ploughed is still able to produce nitrates from urea, which is a natural substance found in urine, but which is also synthesised and sold as a fertiliser to enrich the soil with nitrogen.

Get 3 jars with rubber seals and lids. Sterilise these three jars to destroy any microbes. Bring distilled water or water from an osmosis machine to the boil to also destroy any microbes it may contain. Be careful; tap water may contain nitrates. If you use this water instead of distilled water, your measurements will be distorted.

Checking nitrate concentration in ploughed soil

Nitrate concentration in the right jar appearing as a red haze above the soil. The left jar received the same dose of urea which did not evolve to produce nitrates. The middle jar received no urea.

Take a sample of garden soil about 20 cm deep and from a place that has not been fertilised for at least 1 month. Put this sample in two jars (about 1/3 of the jar). Pour distilled water into the 3 jars when the temperature has dropped to about 25° so that each jar is filled to ½ of its volume. In the jar containing only water and in one of the two jars containing soil, add a large pinch of pearl urea. Do not use urine, which contains aerobic and anaerobic microbes and breaks down very quickly to give off an ammonia smell. Or, use pasteurized urine if your cerebral cortex is allergic to synthetic fertilizers.

Place the jars in a room with a temperature of about 20°C and wait for about ten days. After this time, you will notice the following:

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The jar containing water and urea (which serves as a control jar) shows no change in colour. The urea has not been converted into nitrates.

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In the jar containing soil and urea, a reddish veil suspended in the water above the soil can be seen in the picture above.

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In the jar with soil, but no urea, this deposit is not seen.

The nitrate content in the jars can be measured with a laboratory test tape. It is possible that the control jar with soil contains nitrate residue from an old fertiliser application, which should be compared with the other jar with soil and urea.

Soil fertility; is the apocalypse coming?

An old doomsday theory in agriculture is back on TV.

Crops in stony or desert areas that produce humus

The wriggling of an earthworm that excites a minister

A very simple experiment to check whether a frequently ploughed soil that has received synthetic fertilizers is dead.