by Douglas Barnes
Updated April 3, 2008
Soil is like air. It is a simple thing that gets overlooked and it gets a bum rap: it’s “just dirt.” But “just dirt” is where the nutrients that keep plants healthy come from. And even for people who refuse to eat vegetables, plants are ultimately the source of nutrients in human nutrition. In other words, without healthy soil, there is not healthy food. And without healthy food, there are no healthy people. This often overlooked fact has been a factor in the collapse of many a civilisation and no civilisation that ruined its soil has survived, so we ignore it at our peril.
Permaculturists know that the use of synthetic fertilisers are a great way to damage soil life, but new research shows that the overall effect is actually very dramatic.
Saeed Khan, Richard Mulvaney, Tim Ellsworth, and Charlie Boast, soil scientists from the University of Illinois, found that in one of the University’s Morrow Plots the growth and yields of corn were 20% lower than in another plot.1 Conventional theory would predict the poorly performing plot would have been the better performing one as it received greater inputs of nitrogenous fertilisers and crop residues.
According to Saeed Khan, “What we learned is that after five decades of massive inputs of residue carbon ranging from 90 to 124 tons per acre, all of the residue carbon had disappeared, and there had been a net decrease in soil organic carbon that averaged 4.9 tons per acre. Regardless of the crop rotation, the decline became much greater with the higher nitrogen rate.”
The effect is not limited to this one case, either. Charlie Boast points out that "In numerous publications spanning more than 100 years and a wide variety of cropping and tillage practices we found consistent evidence of an organic carbon decline for fertilized soils throughout the world and including much of the Corn Belt besides Illinois."
Adding soluble nitrogenous fertilisers pushes soil away from a fungal-based soil to a bacterial-based soil (mycorrhizal, saprophytic and epiphytic fungi can greatly boast plant health and yield). But it appears that, in the long run, the addition of synthetic nitrogenous fertilisers makes the soil less hospitable to bacteria as well.
Furthermore, the addition of too much phosphorus kills off fungi; and fungi produce glomalin, which makes up 27% of carbon in soils.2 Glomalin is also very stable in soil, lasting from an estimated 7 to 42 years. And as CO2 levels increase, mycorrhizal fungi respond by increasing the amount of glomalin produced (responding in accordance with the predictions of the Gaia hypothesis). We cannot afford to kill off this natural climate regulator simply for the convenience of running our agricultural systems like a factory.
This loss of carbon not only hinders soil life, it also reduces the water storage capacity of soil as well. The loss of life in the soil will damage the soil structure leading to increased erosion. The loss of carbon in the soil also means more nitrate pollution from runoff as the excess fertiliser not taken up by the plant (i.e. most of the fertiliser) washes away with rainfall and irrigation, polluting aquatic systems. And if that were not enough, the carbon is lost to the atmosphere in the form of CO2, increasing greenhouse gas emissions.
Imagine the effects of a holistic approach to soils. It is reasonable to expect that more than 4.9 tons per acre could be sequestered in soils rehabilitated to maximize soil life.3 But taking 4.9 tons as a conservative figure, the U.S.’s 434 million acres of cultivated land could sequester 2.1 billion tons of carbon, were it to be shifted to ecological farming methods.4
Organic soils have higher numbers of Trichoderma and Piriformospora species of mycorrhizal fungi which help protect against the parasitic Fusarium fungi.5 Fusarium produces vomitoxin, which is not destroyed in the cooking process. Its associated risks include cancer and birth defects. Fusarium also contains the chemical warfare agent fusariotoxin. Infected crops are unfit for human food or animal feed. Losses can be significant, as well. In 2002 for example, farmers in Manitoba, Canada suffered $100 million in losses due to fusarium. 6 It is worth noting that the addition of glyphosate has been found to stimulate the growth of fusarium,7 so following conventional practices greater risks on human health and introduces the possibility of increased losses for the farmer. [Good luck to conventional farmers. The latest news is that the most popular brand of glyphosate, which also happens to have a surfactant that is deadly to amphibians,8 has now doubled in price from last year.9]
Once upon a time, farmers needed to respect soil life. Since the Second World War, however, agriculture has been incorrectly reduced to an industrial process with the belief that simply supplying the right parts (mixes of crop nutrients) is all there is to manufacturing the agricultural product. What we have actually managed, though, is to damage more land in a shorter period of time than any other period in history. And we are doing it on a scale that is global. We can live without oil (believe it or not). We can live without silicon chips. We can even live without industrial manufacturing. We simply cannot live without healthy soil.
The solution is, luckily, simple. Stop wasting money by giving it to chemical manufacturers for products (biocides, etc.) that reduce yield. Stop relying on chemical manufacturers for fertility. Stop wasting energy by ploughing. Instead, recognise that life is interconnected. Build a healthy soil ecosystem and you will be rewarded with healthy plants. But if you approach nature with the ill-conceived metaphor of the machine, you can expect that “machine” to perform poorly.
1. Study reveals that nitrogen fertilizers deplete soil organic carbon http://www.eurekalert.org/pub_releases/2007-10/uoia-srt102907.php
2. Glomalin: Hiding Place for a Third of the World's Stored Soil Carbon http://www.ars.usda.gov/is/AR/archive/sep02/soil0902.htm
3. The mass of bacteria per acre of healthy soil is around 70,000 pounds with only 4500 lb to 5400 lb in ploughed soils (80,000 kg per hectare and only 5 to 6,000 kg per hectare of ploughed land). The figure for actinomycetes would conservatively be around 8,000 kg per Ha (about 7140 lb per acre) but could reach as high as 80,000 kg/Ha (about 70,000 lbs per acre). And after adding the mass of the fungi, protozoa, algae, nematodes, earthworms (one to 1.5 million per acre of healthy soil, not including their castings), and arthropods in the soil, the figure of 4.9 tons per acre more for healthy soils is not a radical estimate at all.
4. Based on figures from the 2002 USDA Census of Agriculture.
5. Bulluck, III, L.R., Brosius, M., Evanylo, G. K. and Ristaino, J. B. 2002. Organic and synthetic fertility amendments influence soil microbial, physical and chemical properties on organic and conventional farms. Applied Soil Ecology 19:147-160 cited in Ho, Mae-Wan and Ching, Lim Li. 2004. GMO Free: Exposing the Hazards of Biotechnology to Ensure the Integrity of Our Food Supply. Vital Health Publishing, Ridgefield, CT; Deshmukh, SD; Kogel, KH. 2007. Piriformospora indica protects barley from root rot caused by Fusarium graminearum. JOURNAL OF PLANT DISEASES AND PROTECTION. 114(6):263-268.
6. Suzuki, D. Dressel, H. 2004. Naked Ape to Superspecies: A Global Perspective on Humanity and The Global Eco-Crisis. Allen & Unwin, Crows Nest, NSW, Australia; Boswell, Randy. 19 August, 2003. Roundup May Harm Wheat: Researcher’s Say Monsanto’s Popular Weedkiller Might Boost Blight. The Leader-Post. Regina, p. A17. Coghlan, Andy. August 14, 2003. Weedkiller May Boost Toxic Fungi. New Scientist; Suzuki, D. Dressel, H. 2004. Naked Ape to Superspecies: A Global Perspective on Humanity and The Global Eco-Crisis. Allen & Unwin, Crows Nest, NSW, Australia; Boswell, Randy. 19 August, 2003. Roundup May Harm Wheat: Researcher’s Say Monsanto’s Popular Weedkiller Might Boost Blight. The Leader-Post. Regina, p. A1; Bigwood, Jeremy. August 20, 2003. Scientists Link GM Crop Weed Killer to Powerful Fungus. IPS; Rahe, J. Can. J. Bot. 33 (1987): 354-360., Appl. Soil Ecol. 8 (1998): 25-33 cited in Scientists Expose Myths that Organic Farming Produces Dangerous E-coli and Plant Diseases http://www.organicconsumers.org
8. Roundup®highly lethal to amphibians, finds University of Pittsburgh researcher http://www.eurekalert.org/pub_releases/2005-04/uopm-rhl040105.php
9. Farmers Feeling Roundup Spike http://www.agbios.com/main.php?action=ShowNewsItem&id=9425