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 µm 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 µm, mainly with pores 50 to 200 µm in size, and phosphomonoesterase only with pores whose size was <500 µm. L‐asparaginase activity was not correlated with porosity. Only arylsulphatase, dehydrogenase, and phosphodiesterase were negatively correlated with bulk density.

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Three respirometric methods were tested using 18 organic matrices. Two methods were performed in the solid state condition using static (SRI) and dynamic approaches (DRI) while the third was performed in the liquid state (SOUR). The results obtained showed that all methods were able to describe biological stability and were well correlated. SOUR gave results that differed from DRI and SRI, which, in turn, showed good agreement. SOUR showed a good correlation with dissolved organic carbon, above all with the hydrophilic fraction, indicating that water media was responsible for the high availability of soluble organic material during initial hours of the test. The use of SOUR cumulative data (OD 12 and OD 20 ) reduced the effect of the soluble fraction on the measurement, thereby increasing the correlation coefficient with the solid state methods.

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ABSTRACTreason the fate of a pesticide in soil can be determined by the complex interactions between the intrinsic prop- Celis et al., 1998aCelis et al., , 1998bCox et al., 2001; have shown that the adsorption of triasulfuron to soil increases in the Gigliotti and Solomon, 2000), mainly due to the high

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