THE APPLICATION OF SECONDARY PAPER-MILL SLUDGES ON ARABLE SOILS TO IMPROVE SOIL FERTILITY

In field investigations the application of secondary paper mill sludges on arable soils was tested. No deterioration could be verified with regard to soil and plant growth. However an improvement was not significant. Accumulation of heavy metals in soils or plants was not observed. There was no risk of soils and plants, because the contents of organic halogen compounds were much lower than the common administrative threshold values. The carbonate content of the sludges was variing very much. This is why a prognosis of the pH-effect was difficult. Nitrogen was fixed in the soil during decomposition of the sludge, which was poor in nitrogen. An application of secondary paper mill sludge on arable soils have to be connected with a fertilization to equalize nitrogen supply. Industrial process should guarantee always a similar carbonate content in the sludge to avoid micronutrients deficiency.