The aim of this experiment was to study the effect of soil contamination by treflan 480 EC on biochemical properties of soil and on the growth and development of crops (spring rape and white mustard). The tests were conducted on leached brown soil formed from clay slightly dusty sand of 5.8 pH in 1 M KCI, to which the following quantities of treflan 480 EC were added: 0, 1.5, 3.0, 4.5, 6.0, 9.0 and 12.0 mm(3) . kg(-1) of soil. The biochemical analyses were performed 7 days after the experiment was established and during the flowering of plants.
It was found that treflan 480 EC had a negative influence on the activity of dehydrogenases, urease, acid phosphatase and alkaline phosphatase. Spring rape and white mustard were intolerant to high concentrations of treflan. The yield of crops was negatively correlated with the herbicide rate. Potential biochemical index of soil fertility derived from the activity of dehydrogenases, urease, acid and alkaline phosphatases as well as the content of organic carbon were negatively correlated with the concentration of treflan in soil, but positively correlated with the yield of spring rape and white mustard.