The effects of long-term open-air fumigation with SO on a field crop of broad bean (Vicia faba L.) I. Depression of growth and yield.

In an open-air Held exposure system for the controlled release of air pollutants, broad bean (Vida faba L.) crops were exposed to elevated SO concentrations in three growing seasons, in order to analyse the effects on crop growth under field conditions. The treated plots were exposed to a mean concentration of 165μgm in 1985, 62μgm in 1986 and 74μgm in 1988. The background concentration was about 10μ m . A reasonably uniform distribution of SO concentration was obtained over an area of 8m × 8m and concentrations exceeding the target concentration were rare. In 1985 and 1988, the growth rate of the crop was depressed at the end of the pod-filling period. This resulted in a reduction of total dry-matter production of 17% in 1985 and 9% in 1988, and a seed yield reduction of 23% in 1985 and 10% in 1988. In 1986, dry matter growth was not analysed up to the end of the growing season due to a severe infection of Botrytis fabae (Choclate spot disease) infection in the control plot in the middle of the pod-filling period. Slight B. fabae infections in the control plots only were also observed in 1985 and 1988. In all experiments no significant reductions of dry matter growth were observed in the vegetative and early reproductive phases.