EFFECTS OF AMBIENT AIR-POLLUTION ON WHEAT AND RICE YIELD IN PAKISTAN

Open-top chambers ventilated with ambient or charcoal-filtered air wer e used to assess the impact of air pollution on the yield of local cul tivars of wheat and rice, at a site on the outskirts of Lahore. At thi s location, 6-h mean O-3 concentrations reach 60 ppb in certain months , and annual mean NO2 concentrations are 20-25 ppb. The experiments sh owed significant yield reduction in two successive seasons which range d from 33% to 46% in wheat and from 37% to 51% in rice. The major yiel d parameter affected was the number of ears or panicles per plant, alt hough there was also evidence of snail effects on 1000 grain weight an d on the number of grains per ear/p anicle. These results have signifi cance in terms of the maintenance of agricultural yields as pollution emissions rise in south and south-east Asia.