The effects of cement dust emissions from a cement factory on the growth and yield of trees in the adjacent Olive plantation were investigated. Some characteristics of the soils in the polluted and non-polluted areas of the plantation were studied.

In the polluted area the cement dust had formed a crust ca 1 cm thick on the soil surface, and the leaves of Olive trees in this area were also covered with a cement crust. The amount of dust deposited on the leaves of the polluted trees was around 2.55 mg/sq. cm of leaf surface, but they did not show any visible symptoms of injury. However, as compared with a non-polluted tree, the polluted trees showed up to 50 and 55.6 per cent reduction in growth and fruit yield, respectively. Moreover, the length and width of the fruits of the polluted trees were, respectively, some 15 and 20 per cent shorter.

As regards herbaceous plants, there were only 6 species growing in the polluted area and these were practically confined to the soil under the trees whereas there were 26 species growing virtually at random in the non-polluted area. The soil of the polluted area had a lower moisture-content, less organic matter, a lower water-holding capacity, and a markedly reduced content of calcium carbonate, than that of the non-polluted area, which, however, had a somewhat lower content of other salts.

The marked reduction in the growth and yield of Olive trees in the polluted area may be explained in terms of the shading effect of the foliar cement crust as well as through the changes in soil characteristics that had been brought about by the cement factory effluents. Thus the uncontrolled emissions of a cement kiln can affect the growth of the adjacent vegetation through both the air and the soil.