How the crops can vanish into dirty air

POLLUTION (2)

By NIGEL HAWKES Science Correspondent

AIR POLLUTION could be nibbling away at the British cereal harvest, in some cases cutting it by more than half, according to botanists at the Rothamsted Experimental Station in Hertfordshire.

Experiments in the fields near the brickworks of Bedfordshire have shown that barley yields could be cut by as much as 60 percent in some circumstances. If these findings are typical of the country as a whole, annual losses could run into millions of pounds.

The experiments were done by growing the plants in ordinary soil inside a variety of plastic chambers. In some chambers, the air was filtered to remove the sulphur-dioxide and fluoride pollution; in others, the air was unfiltered.

Filtered chambers produced yields almost double those of crops in unfiltered ones. And the yields in the filtered chambers were almost 60 per cent greater than those in the open fields.

The scientists who did the experiments, Dr Charles Whittingham, Miss Alison Brough and Mr Martin Parry, conclude in the latest issue of Chemistry and Industry that pollution ‘at levels previously regarded as acceptable may be causing significant yield losses in British agriculture.’

The authors are cautious because of the difficulty of ensuring that the chambers themselves did not affect the outcome. A variety of different chamber designs were used to try to eliminate such effects.

Pollution levels around the brickworks, though higher than the rural average, are by no means exceptional. During the growing season the average sulphur-dioxide level was 61 micrograms a cubic meter, against an annual national figure for rural areas of 35 to 40 micrograms a cubic metre.

Dr Whittingham estimates that perhaps 20 per cent of the total area under cereals in Britain has sulphur-dioxide as high as or higher than those in the brickfields. In Lancashire, the average runs at about 120 micrograms, with occasional peaks as high as 500 micrograms.

The team has extended its operations to Lancashire and is studying the growth of grass on a farm run by the Ministry of Agriculture. Earlier work in laboratories produced a mass of contradictory data, sometimes even indicating that sulphur pollution helped plants to grow.

Only experiments in real conditions can establish the truth. Dr Whittingham believes that the damaging effects of pollution are increased when the plant is already under stress, and one reason the experiments show such a big effect is that they were carried out in the dry, hot summer of 1976.

If the results are confirmed by further work, Dr Whittingham says that the most effective way to tackle the problem would be by breeding varieties of plant resistant to pollution. Already, he says, different cultivated varieties of barley show different sensitivities to pollution, so it should be possible to select varieties for growing in dirty areas.

The alternative, of reducing the pollution, might seem more logical but would be difficult and expensive. Sulphur pollution is produced all over Europe and respects no boundaries; reducing it would involve an investment of thousands of millions of pounds. ‘The best answer will be to attune the plant to live with the pollutant,’ Dr Whittingham says.