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Project ID: ICA3-CT-2002-10033
Finanziato nell'ambito di: FP5-INCO 2
Paese: Italy

Use of OMW as Fertilizer of Soils Deficient in organic matter

Experiments performed under laboratory conditions evaluated the effect of OMW on chemical and biochemical properties of soil. A soil from Morocco 4 was used to simulate conditions likely occurring in that Country. The changes of the activities of several enzymes involved in the cycles of main nutrients, soil respiration, and microbial biomass-C and -N of the soil, amended with OMW at two different rates (equivalent to 40 and 80 m3 ha-1) were determined at different incubation times. An unamended soil was used as a control. The residual phytotoxicity of treated and untreated soil was also evaluated by performing germination tests using soil as germination medium.

The obtained results indicated that several concurring activating and/or inhibitory effects occurred (increased enzyme production, presence of inhibitory OMW ions and/or OMW compounds, and/or their metabolites, release of soluble ions from soil components etc.). Furthermore, transformation processes of OMW phenols catalysed by Mn and Fe soil components took place and decreased the phytotoxicity of soil. As regards chemical and physical properties no significant differences of the physical-chemical properties of the soil were observed at the two OMW/soil ratios. As regards biochemical properties the enzyme activities of C cycle, dehydrogenase and beta-glucosidase, N cycle, urease and nitrate reductase, P cycle, phosphatase, S cycle, arylsulphatase, and aspecific hydrolases, fluorescein diacetate hydrolase, varied widely in soil samples with and without OMW treatment and with time.

Experiments were performed on the effect on the same soil properties after the application of OMW before and after a detoxifying treatment able to reduce consistently their phenolic content. The obtained results indicated that the enzymatic activities in soil with detoxified OMW (i.e. with a lower amounts of monomeric phenols) are generally lower than those of the soil added with OMW without any previous treatment, except for FDA-hydrolase. When detoxified OMW was used, the majority of parameters showed a consistent increase after 7-14 days from treatment followed by a gradual decrease. After 56 days from treatment, some parameters reached the initial level (for example the biomass carbon) and other ones stabilized at higher activity levels (for example the biomass nitrogen).

As regards germination tests soil phytotoxicity suddenly increased immediately after the addition of the highest OMW amount, whereas only 20% reduction of germination occurred with the lowest OMW rate. However, a reduction of phytotoxicity was observed with increasing the incubation time. An interesting result was obtained with OMW after the removal of monomeric phenols. When treated OMW were used, the restoration of a non-phytotoxicity environment is reached in few days and it was complete; in contrast, when untreated OMW were used, the reduction of phytotoxicity was very slow and never was complete.

These results obviously suggest that the use of OMW without monomeric phenols is less harmful on soil properties than untreated OMW.

Informazioni correlate


Liliana GIANFREDA, (Full Professor of Agricultural Biochemistry)
Tel.: +39-081-25392179
Fax: +39-081-2539186