The paper presents the results of the researches carried out at the Agricultural Research and Development Station Oradea, Bihor county, between 1993 and 2002, regarding agricultural yield from a preluvosoil polluted under control with oil brought from the exploitation site at Suplacu de Barcău, Bihor county. The experimental device was made out of micro parcels of 1 m², set up in a randomized manner, in a Latin square, polluted with concentrations of: 0, 1, 3, 5 and 10 % (0, 3, 9, 15, and 30 l/m²), oil in the ploughed layer, in 4 repetitions. The experience was cultivated in the first three years with millet, a plant which is considered to be resistant to pollution, and than until 2002 with spring wheat. The analysis of the yield losses from the parcels polluted with oil in various concentrations, have shown that these decreases in time, without any sort of agropedomeliorative measures. Starting from this observation this paper is commited to evaluating the influence of the climate factors, rainfall and temperatures, on the biodegradation process, through the accomplished yield losses of millet and wheat, in the research period. The climate conditions characterized by annual rainfall (661,2 mm) and temperature (11,0 ºC) show that the 10 year period studied had with 26,2 mm more rainfall than the annual average and was warmer with 0,5 ˚C. The yield losses (%) of the variants polluted under control with oil residue have, in time, a decreasing tendency, demonstrating a biodegradation of pollutant and a decrease of the effect pollution has on yield. By analyzing the correlations between the millet yield losses in the first 3 years of research and the spring wheat yield losses registered in the last 7 years and respectively the climate factors (rainfall and air temperature) registered in the vegetation period, very significant square, polynomial  correlations were established for each oil concentration. The 3D representation of this presents for each concentration a maximum value of yield losses at different values of rainfall and air temperature. For the variants with high pollutant concentration (3, 5 and 10 %) maximum positive differences of yields are obtained for maximum rainfall sum (600 mm) and maximum air temperature (17,5 ºC), the moderate humidity and high temperatures stimulate the activity of the microorganisms responsible for soil oil degradation.

oil pollution; preluvosoil; biodegradation

Presentation: oral