Role of compost, bentonite and calcium oxide in restricting the effect of soil contamination with petrol and diesel oil on plants.

The studies have been initiated to find a way to use compost, bentonite and calcium oxide in order to reduce the effect of contaminated soil with a small amount of petrol or diesel oil on the yield and nitrogen content in crop plants--spring rape and oats cultivated as the main and aftercrop. Petrol and diesel oil had a toxic effect on the growth of the plants and modified nitrogen content, with the intensity of the effect depending upon their type and dose and on the type of applied substance reducing the effect of oil derivatives. Spring rape (main crop), was more sensitive, and oats (aftercrop) was less so. Petroleum-derived substances reduced the yield of spring rape by a maximum of 73% for petrol and by as much as 99% for diesel oil. Nitrogen content was higher for spring rape than for oats and larger for petrol than for diesel oil. Adding bentonite, calcium oxide or compost to the soil contaminated with oil derivatives usually reduced the negative effect of petrol and diesel oil on plant growth and reduced the protein nitrogen content and increased the total nitrogen content in plants. Bentonite proved to be the most effective, with calcium oxide and compost slightly less so. The most positive results were obtained for spring rape as the main crop. An addition of compost, bentonite and calcium oxide to soil had a stronger modifying effect on nitrogen content in plants on soils contaminated by diesel oil than petrol.