URBAN WASTE COMPOST - EFFECTS ON PHYSICAL, CHEMICAL, AND BIOCHEMICAL SOIL PROPERTIES

A long-term field experiment was conducted to determine the effect of the additions of urban waste compost on the physical and chemical properties and enzymatic activities in a calcareous soil (Fluventic Xerochrept). Total porosity (pores >50 mu m measured on thin soil sections from undisturbed samples by image analysis) was greater in the plots treated with compost than the control plots due to a larger amount of elongated pores. In the amended plots total and humified organic C, Pb, Cu, and Zn showed a significant increase compared with nonamended plots. Enzymatic activities (L-asparaginase, arylsulphatase, dehydrogenase, phosphodiesterase, and alkaline phosphomonoesterase) were significantly enhanced by the compost addition thus indicating no inhibiting influence of the heavy metals present. The increased levels of the arylsulphatase, dehydrogenase, phosphodiesterase, and phosphomonoesterase activities were significantly correlated with total porosity: the first three with pores ranging from 50 to 1000 mu m, mainly with pores 50 to 200 mu m in size, and phosphomonoesterase only with pores whose size was <500 mu m. L-asparaginase activity was not correlated with porosity. Only arylsulphatase, dehydrogenase, and phosphodiesterase were negatively correlated with bulk density.