While a systematic Literature Review to identify the difference between organically and conventionally produced foods is welcome, it needs to be recognised that this is an academic study performed by a group with little or no practical field experience. Moreover, it should be explained that organically produced food is supplied by farmers who follow traditional practices of food husbandry: conventionally produced food is mostly produced by farmers who have adopted innovative methods which have been introduced during the last 60 years. The word ‘conventional’ seems to have been adopted and used to provide spurious authority to innovations introduced for short-term commercial rather than husbandry reasons. In order to discover the differences between conventional and organic crops it would have been best to start by asking the opinions of farmers with first-hand experiences of feeding them to livestock. There is a mass of anecdotal information available that has never been collected and analysed. It would also have been desirable to learn a little of the history of the Soil Association, the organisation which has developed the market for organic produce; and to have had experience of the changes which have taken place in fertiliser usage.

After a series of disastrous experiences I stopped using nitrogen fertilisers upon my farm in 1980. The improvements in the health of my livestock that followed were so remarkable that I asked several authorities, ‘Have your fertiliser recommendations been properly tested upon acidic soils, and do they induce trace element disorders in crops and livestock?’  As far as I am aware this vital question has never been answered. Had it been, the Food Standards Agency would be better informed and there would have been no need to commission the present study by LSHTM (London School of Hygiene and Tropical Medicine).

The soils of the UK are remarkably variable. Some are derived from igneous rocks but others are sedimentary, in origin, some are rich in organic matters but others contain little, and their pH ranges from being very acid to being very alkaline. Despite this variability modern fertiliser recommendations differ little from one locality to another and are substantially based upon work done at Rothamstead despite the soils in the south and east of England being very different to those that predominate elsewhere.

Lady Jean Balfour and her associates set up the Soil Association in the 1930s because they disapproved of the increasing  use of artificial fertilisers such as ammonium sulphate and superphosphate. Initially the SA made little impact, but a fresh group of enterprising office holders were elected in the years following 1980 and they have made it the influential organisation it has become today with views on every aspect of agricultural husbandry and food production. Despite the importance of many of these matters the fact remains that the main influence upon food quality, and especially its mineral content, remains the use of fertilisers.

Until 1960 basic slag, superhosphate and 15.5% Nitrogen Nitrochalk were widely used, but since then these and other fertilisers have been replaced by a range of concentrated high nitrogen fertilisers which contain no gypsum (CaSO4). The replacement of gypsum and ammonium sulphate by ammonium nitrate (34.5%N) enabled farmers to be easily persuaded to apply up to 200 units of N per acre per annum to pastures grazed by dairy cattle (about double the previous rate). This  initially ignored the discomfort caused to the cows, the increased volume of silage effluent, and the pollution of water courses. Cereal husbandry was also altered; new varieties were introduced and outside the UK the ‘green revolution’ was initiated.

Just as today the problems associated with the introduction of GM crops are being minimised, so in the past the problems with the green revolution were little published.  I have for instance been told that since a farm in Cheshire, which had been owned by a fertiliser company, has been sold no one has been able to farm it profitably and that the profitability of many neighbouring farms has been adversely affected by the use of too much fertiliser.

Most agricultural scientists are of the opinion that the high nitrogen range of fertilisers is acidic. This does not have a good scientific basis, is simplistic and misleading. It is true that the ammonium ion is oxidised to acidic nitrate by bacterial activity at the soil surface where there is ample oxygen, but there is also bacterial activity in the rhyzosphere where there can be an oxygen deficit. In the UK most alkaline soils are also porous and nitrate cannot be reduced to ammonium because there is insufficient reduction potential at root surfaces; thus nitrate passes directly into roots. The situation in acidic soils is quite different because not only is there a ready supply of protons but an oxygen deficit can develop at root surfaces. In this situation nitrate and certain other anions can be used by bacteria as electron receptors. 

The absorption by plant roots of ammium (a cation) instead of nitrate (an anion) alters the balance of minerals in crops, more anions such as chloride and sulphate are absorbed but fewer of the more important cations like calcium, magnesium, iron, manganese and cobalt. Nor is this all, the shortage of protons which develops in the rhyzosphere causes protons to be sequestered from species such as carbonic acid and dihydrogen phosphate to form highly reactive monohydrogen ions which rapidly combine with the precipitate the essential cations which would otherwise enter roots.  It is sometimes possible to observe with the naked eye deposits around plant roots in which iron clearly predominates. 

Once cobalt has been made insoluble clover will not fix nitrogen and will sometimes not grow. At the same time molybdate can be released from soil minerals and be taken up by crops of grass intended for livestock production, and selenate can be reduced to selenite and deposited with iron etc on root surfaces. When cows graze heavily fertilized grass they often develop selenium deficiency and this renders them susceptible to conditions such as BSE and bovine TB. They also require to be supplied with large amounts of salt to make good that lost in their urine, The results of soil analyses are rendered invalid and soil pH becomes stabilised at about 6.4.

Because they contain more DNA than diploid varieties modern polyploidal cereal varieties require more selenium. Consequently polyploidal varieties perform very poorly where there is insufficient selenium available and especially on soils with a high ferric content. Their failure to compete enables weeds with few chromosomes to flourish. 

While the failure of soil scientists to admit that the use of high nitrogen fertilisers on acidic soils can be counterproductive represents a monumental blunder, a further blunder has been committed by nutritionalists who have failed to make
good the decrease in dietary selenium which followed the replacement of high selenium Canadian wheat with low selenium European wheat. These two blunders, together with the wide spread and perverse refusal to recognise that a selenoprotein is required to activate thyroxine, seem to have led to the predominant cause of illness in the UK now being hypothyroidism. The increased incidence of obesity and type 2 diabetes was remarked just a few years after the importation of Canadian wheat was stopped.

 As the fundamental difference between organic and conventional agricultural systems is philosophical rather than scientific, the application of scientific methods in an attempt to determine differences in food quality is unlikely to provide a clear result.  The wrong question is being asked. The question which should be asked is the same as should have been asked 50 years ago when high nitrogen fertilisers were being introduced. The question is, ‘Does the use of high nitrogen fertilisers upon acidic soils adversely affect the mineral content of produce?’ Because the use of high nitrogen fertilisers increases the mineral content of crops grown upon calcarious soil it does not follow that the same is true for crops grown upon acidic soil.

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First Publlished in 2009

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