News analysis: Organic methods are viable, but benefits to environment remain hidden in the soil

Organic farming is good for the environment. That statement might appear to be a self-evident truth, but there has been little hard science to prove it until today and the publication of a study in the journal Science.

Organic farming is good for the environment. That statement might appear to be a self-evident truth, but there has been little hard science to prove it until today and the publication of a study in the journal Science.

A team of Swiss agriculturists has just completed a 21-year comparison of organic farming, which uses no synthetic fertilisers or pesticides, and its conventional cousin, which relies heavily on agrochemicals. The team concluded that although organic farming produced significantly smaller yields than the conventional approach, the draw- back was more than compensated for by the long-term benefits to the environment.

The findings are based on comparing yields with the amount of fertilisers and pesticides sprayed on five types of crop: potatoes, barley, winter wheat, beets and grass clover. Although the organic fields produced on average a 21 per cent lower yield, they needed between 34 and 51 per of the amount of minerals and other nutrients used on the conventionally farmed fields.

Paul Mäder, of the Swiss Research Institute of Organic Agriculture in Frick, and the leader of the team, said the findings indicated that organic farms used their resources more efficiently and that, in the long term, the organic approach was a commercially viable alternative to conventio- nal farming. "These results should be encouraging for farmers, because they can see that yields are stable over time and that soil fertility has increased," Dr Mäder said.

The study showed organic farming produced more food with less energy and fewer resources – a contradiction of many criticisms of the organic approach, which have emphasised its inefficiency and lack of productivity.

Proponents of organic farming, such as the Soil Association in Britain, frequently assume that it must be better for the environment. In reality, there have been few long-term studies to back up this claim.

The Swiss study, however, found that the organic soil in the experiments was richer, with a larger and more diverse range of beneficial organisms than the soil farmed conventionally. The organic soil harboured more microbes involved in nutrient recycling, more earthworms and more pest-eating spiders and beetles. Because the study ran over many years, the scientists were able to make a statistically valid comparison.

"Soil fertility and biodiversity develop slowly, and this is why a long-term study is essential," Dr Mäder said. "There is a need to evaluate alternative farming systems as a whole system in a scientific way. The most appropriate method to do this is still to conduct long-term experiments, which can be analysed statistically and performed under identical soil and climate conditions."

Although many of the high-profile supporters of organic farming, such as the Prince of Wales and the broadcaster Jonathan Dimbleby, will no doubt find comfort in the Swiss study, some critics are not swayed by it.

Anthony Trewavas, professor of plant biochemistry at the University of Edinburgh, said the Swiss study was severely limited in what it demonstrated about organic farming conducted elsewhere in the world. Field size and climate in Britain were different from Switzerland, Professor Trewavas said. "Unfortunately, the data in the paper suggests that no extrapolation can be made to other soils, climates or countries. The yields of wheat [in the Swiss study] are low, well under half what would be achieved in the UK," he said.

Professor Trewavas has been one of the sternest critics of the organic farming lobby. Two years ago he wrote an article in the journal Nature that questioned the widespread assumption that organic farming was good for the environment. One of his main criticisms of the Swiss research was that it did not take into account a recent innovation in conventional farming where seeds are drilled directly into the ground, with minimal ploughing.

"Ploughing is the most dangerous thing you can do to the soil," Professor Trewavas said. "The plough disturbs ground-dwelling animals, it allows nutrients to be washed away in the rain and it encourages soil erosion."

A similar comparison of organic and conventional farming in Britain, named after a farm called Boarded Barns in Essex, had found that "no-till" conventional farming was better than the organic alternative, with, for example, double the number of earthworms in the soil, Professor Trewavas said. "Organic farmers have to plough to eliminate weeds and bury weed seeds. Weeds are the major problem with organic farming."

No-till conventional farming used one third of the fossil fuel energy of organic farming when calculated on a yield basis, he said. "Organic farming simply wastes energy by having to plough. Herbicide- resistant crops are the way forward here. A single treatment with innocuous herbicide, coupled with no-till conventional farming, avoids this damage and retains organic material in the soil surface."

Another assumption about organic farming is that it causes fewer nutrients to be washed into streams and rivers, reducing dame to wildlife. In fact, there is some evidence that applying manure, the preferred organic fertiliser, rather than chemicals rich in nitrates and phosphates can be just as polluting. Indeed, one study by the publicly funded Rothamsted research station in Hertford- shire found that nutrient run-off from manured fields was higher than from conventionally farmed fields, Professor Trewavas said. Another issue that had to be addressed was the damage to crops from pests. The Swiss study showed pests were a more serious problem for crops grown organically. Professor Trewavas said the study seemed to confirm the fear that organic farms could act as repositories of disease.

The arguments are far from over. What is clear from the Swiss study is that more comparisons are needed to assess the long-term effects and support the belief that organic invariably means "good for the environment".