Specific biomarkers useful to evaluate the soil degradation level and the soil response (resilience) to regeneration practices have been tested and evaluated by the research group of "Soil Biochemical Fertility" at the Unit of Soil Chemistry of ISE-CNR.
The biomarkers are part of an enzymatic pool made up of some hydrolases and oxidoreductases which reflect soil metabolism and are responsible for the mineral nutrient release from natural organic macro-compounds (cellulose, proteins, lipids, lignins). The enzymatic pool also includes extracellular enzymes, less studied but very important, which represent a continuum between the soil biological and the physical world, in that they are strongly linked to humic substances and mineral colloids. These umo-enzyme complexes, defined geo-enzymes (or stable nucleus) have been extracted and purified, from different soil types from Mediterranean environment, and proposed as the last biological barriers of a soil under a process of irreversible degradation (desertification).
The research has a scientific interest and practical aspect, as it is clear from the many contracts financed by public and private structures, and it is carried out by a group which, for a long time, is involved in the conservation of soil fertility, in the transformation and improvement of organic biomass, and in the recovery/recycle of wastewaters as a strategy of natural resource preservation.
Enzyme biomarkers were evaluated in different situations of soil under natural or anthropogenic stress. Experiments to study appropriate techniques of soil biological fertility regeneration through organic biomass recycling have been planned in cooperation with Spanish researchers in the framework of cooperative projects CNR/CSIC.
For example, the application of different types of organic residues in different degrees of stabilization has been used as a practice to regenerate a mine spoil soil (Meirama, Galicia, Spain) and to biologically regenerate seriously degraded soils (Murcia, South-East of Spain). In these cases, compost application activated the formation of humic polymers and humo-enzyme complexes in situ due to the activity of pioneer authoctonous bacteria.
The practice of fertigation, using wastewaters has been studied in an European LIFE project "MIFER" (Microfertigation), to study the biogeochemical aspects of soils in coastal areas of Tuscany, and in a project directed by the Ente Autonomo Flumendosa (Cagliari) and financed by Sardinian Region, to verify the stability of humo-enzyme nucleus after irrigation practices. MIFER demonstrated the possibility to save 50% groundwater and fertilizers by root-zone fertigation practice with humic-enzyme substances, also ensuring preservation of plant yields and soil quality (figure 1, 2). The Flumendosa's project has shown the resistance of the active humo-enzyme complex of Sardinia Islans soils against repeated irrigation practices, but degradation of the labile soil organic matter fractions has not been excluded.
The researches proceed to confirm the presence and role of the humo-enzyme nucleus as a biochemical marker of soil quality in other Mediterranean environments and in extreme extra-Mediterranean climate (Etiopia and Cuba, CNR project). The researches give a strong contribute in the strategies to combat soil desertification through an appropriate management of the soil biochemistry.
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