ET - What's so great about organic?

It is a myth that modern intensive farming is more environmentally damaging, says Tony Trewavas. What's so great about organic? Manure produces nitrous oxide and methane - both potent greenhouse gases

FOR consumers shaken by salmonella, foot and mouth, BSE and GM food, organic farming is often heralded as the saviour of the food chain by vocal supporters, including the Prince of Wales.

According to the mantra, organic farming is more friendly to the environment and more sustainable than traditional intensive methods. Indeed, its aims are hard to quarrel with, from the maintenance of soil fertility and animal welfare to avoiding pollution.

But the lack of scientific studies means that many important claims - that organic food is healthier, that natural pesticides and soil supplements are less harmful, and that wildlife are better off - cannot be substantiated.

Supporters of organic farming have said that such food is superior and is more healthy. Hundreds of rigorous tests have failed to reveal better-tasting properties or improved nutritional value, but have consistently shown that organic produce has lower nitrate and protein content. The health benefits are unclear.

But this may not be the whole story: toxins from contaminating fungi (which can be controlled by specific fungicides) contribute to European cancer rates - fumonisin and patulin are both reported to be higher in organic products, and failure to use effective fungicides has led to organic farms acting as repositories of disease.

Indeed, conventional farmed food seems better for children. Cancer rates have dropped 15 per cent during the era of synthetic pesticide use; stomach cancer rates have dropped 50-60 per cent, probably an effect of plentiful, cheap conventional fruit and vegetables.

Two principles distinguish organic farming: soluble mineral soil additives are banned and synthetic herbicides and pesticides are rejected in favour of natural pesticides.

The reduction in pesticide use does lead to higher levels of some insects and birds on organic farms. But current synthetic pesticides are very unstable and only short lived declines of most field insects are reported, even when the maximum dose is used. Lower levels of aphids on organic farms could reflect lower nitrogen and protein content of crops, and lower yield - there are fewer plants for the pests to eat. Indeed, when we look at the a ratio of crop yield/aphid population, the difference between organic and intensive farming is negligible.

Underlying our concerns about the environment are worrying statistics about the decline in the range and number of species on farms. But it is often overlooked that some conventional mixed farming can maintain diversity.

Mixed farming in smaller plots, or farming based on the traditional ley (for example wheat undersown with legumes) maintains conventional yields and low costs. The benefits for wildlife equal those provided by organic farming but at lower cost to the consumer.

Competitive organic farmers keep fields clear of weeds using frequent mechanical weeding, which harms nesting birds, worms and invertebrates. They use more fossil fuels, which greatly increases pollution from nitrogen oxides. A single treatment with innocuous herbicide coupled with no-till conventional farming avoids this damage.

Similarly, while higher, beneficial levels of earthworms are often reported in organic fields, reflecting the dependence on manure, there are problems with the use of manure to boost soil quality, while conventional crop rotation seems equally effective.

Manure breakdown cannot be synchronised with crop growth but continues throughout the growing season. When legume crops are ploughed in (a necessary part of the organic method to build soil fertility) the continued breakdown leads to nitrate leaching into aquifers and waterways at identical rates to conventional farms. Degradation of organic material from manure produces significant amounts of nitrous oxide and methane, potent greenhouse gases. The variable composition of manure has varying effects on crop growth.

The use of soluble mineral salts prohibited by organic regulations is also contentious. Minerals taken out of farmland as produce must balance those put back by other means; organic farmers typically rely on legume nitrogen fixation, rain water or mineral recycling in the farm. The few detailed accountings suggest slow but accumulating mineral deficits, particularly of potassium and phosphate, in organic farmlands.

Developments in the past 25 years have shown how conventional agriculture can be more sustainable and environmentally friendly than organic. An intensive farm can match organic yields using only 50-70 per cent of the farmland. Excess food is being produced in Europe, hence farmers are being encouraged to set aside up to half of their land for fast-growing willow plantations which are frequently coppiced for fuel.

With this novel conventional approach, now in commercial operation throughout Europe, total fossil fuel use and carbon dioxide production is lower than in organic farming, and because of carbon recycling it is more sustainable.

The plantation of willow trees with its undercover of weeds, mammals (including deer) and insect refuge and bird-nesting sites outperform organic farms on any biological measure of environmental diversity. However this practice crucially depends on the most efficient use of land for food production.

M odern agriculture, with its single-crop monoculture system, is claimed by organic proponents to be inherently unstable and unsustainable. It is true that crops rapidly disappear from fallow fields, as they cannot compete with weeds, but wild, stable monocultures of species such as phragmites, wild wheat, (genetically uniform) spartina and mangroves indicate that ecological stability is not understood. Furthermore, although mixed cropping (supposedly mimicking ecological diversity) can reduce disease, some combinations accelerate disease spread.

In the search for a more environmentally sensitive approach, integrated farm management combines the best of traditional farming with responsible use of technology, integrating care for the environment with safe, efficient methods of production. Detailed information on soil structure and field fertility is used to target minerals and integrated pest management to control pesticides and avoid waste.

Integrated farm management is a prime example of how to retain the benefits of technology while minimising the problems. Yet, unlike organic farmers, who receive money for conversion, no aid is given by the government to those who learn integrated farm management or encourage its successful use.

Organic farming is glibly backed as the only alternative to intensive farming, a "holistic" approach that is kinder than the "chemical" approach. We should ignore this dogma and focus on the real issue: how to produce high yields efficiently and improve species diversity using tried and tested methods. We need rigorous science, not ideology.

Tony Trewavas is a professor at the Institute of Cell and Molecular Biology, University of Edinburgh. The current issue of Nature carries a longer version of this article

'Natural' pesticides are dangerous

Approved pesticides for organic farmers include:

rotenone, recently shown to induce Parkinson's disease

copper sulphate, which has caused liver damage in vineyard workers, kills worms and is persistent in soil and produce (to be banned by the EC after 2002)

Bacillus thurigiensis spores, causing fatal lung infections in mice

-- Anonymous, April 03, 2001

Answers

A rather unbalanced discussion (IMO).

OF COURSE some "natural" pesticides are toxic, they were intended to be. Organic Gardening magazine never considered substances like rotenone appropriate (e.g., harmless to humans) for an organic garden. However, some pesticides are quite species specific, or at least quite harmless, like the light refined oil sprays.

In my "organic" garden, I don't use fertilizers that contain a water- soluble nitrogen component of more than 1.5%. That appears to be the break-off. There should be a higher non-water-soluble component listed on the label.

Can't accept that poisoning the microbes is an example of sustainable agriculture, and that's what happens with the synthetic fertilizers which are typically very, very high in water soluble nitrogen. Can't be good in the long run. It's also not true there is no real data on this. One of my gardening bibles is "Edaphos: Dynamics of a Natural Soil System" by Paul D. Sachs, available in paperback from Amazon for $14.95 plus shipping. I could NEVER go back to synthetic fertilizers after digesting that book. Required reading IMO.

I am concerned about whether BSE will have touched organic practices. I'm thinking in particular of bone meal and blood meal. If you aren't allowed to donate blood if you were in a high risk country, then someone has reason to believe it could be transmitted by blood.

-- Anonymous, April 04, 2001

I wondered if anyone would take this person to task! And we didn't even get into mineral-depleted soil and the destruction of biodiversity from growing the same crops in the same place over and over and over for decades.

-- Anonymous, April 04, 2001