Effect of pig slurry on increase of biodegradation of petroleum products in soil

Fertilization of haylage oat in 1995 and winter rye for green forage in 1996 by pig slurry increased intensity of soil nitrification during growing season what was confirmed by finding actual nitrate content in soil. Positive effect of slurry on microbial processes in soil is given by a close ratio in slurry-contained carbon and nitrogen. Pig slurry at relative surplus of nitrogen represents a suitable nutritive substrate for soil microbes supporting their development. Soil contamination by gear oil and diesel oil in 1995 before sowing of haylage oat reduced intensity of soil nitrification. Application of pig slurry in contaminated soil reduced the negative impact of petroleum products on soil nitrification in the first growing season, and fully eliminated it in the second growing season (Tab. I). The course of biodegradation of petroleum products in soil was investigated through the ratio of hydrocarbons of n-heptadecane to pristan (C17/pri) and n-octadecane to phytane (C18/fy). In indirectly proportional relationship between decrease of I:these values and level of biodegradation a positive effect of pig slurry on biodegradation of particularly in case of petroleum products in soil (Tab. II) was confirmed (Tabs II and Ill). Another binding indicator of the degree of soil contamination by petroleum products is the content of nonpolar extractable substances (NEL). Analyses conducted proved the decrease in their content in soil due to applied slurry (Tab. IV). The effect of petroleum products on the biomass dry matter production biomass of haylage oat and winter rye on green forage was also evaluated in field trials (Tab. VI). Dry matter production was reduced in both cultivated crops on soil contaminated with oil and crude oil compared with uncontaminated soil. In oat it was by 25.11% due to oil, by 41.78% due to crude oil. In winter rye in the first case it was by 11.76%, in the second case by 15.44%. Addition of slurry reduced the negative impact of oil and crude oil on the biomass dry matter production of both experimental crops by acceleration of biodegradation of investigated petroleum products in soil.