Chemical and microbiological characterization of olive-mill waste-based substrata produced by the O.Mi.By.P. technology and their grounds amendment

摘要

An innovative technology for pomace and olive-mill wastewater recycling for agronomic goals was highlighted by the Oliveculture Section of the Institute for Agricultural and Forest Mediterranean Systems, National Research Council, Perugia, Italy, in the context of the European project Life Environment - Tecnologie Innovative per il Riciclaggio delle Sanse e delle Acque di Vegetazione (TIRSAV). Olive wastes without stones are mixed with appropriate hygroscopic organic wastes, producing a non-percolating and non-bad-smelling substratum, where aerobic microbial metabolisms occur. Substrata are packaged in net sacks, stored and amended on-site as requested by cultural conditions. In this work, two experimental storage systems were compared for physical,chemical and microbiological modifications: (i) outdoor stratification of net-sack substrata, protected against precipitation; and (ii) net-sack substrata piled inside a warmed greenhouse. In addition, different substrata were tested as amendment/fertilizer at a rate of 6 tonnes/year of dry matter per hectare in an intensive olive grove in comparison with a standard mineral fertilizing system, and vegetative and productive parameters were recorded over four years.Important chemical changes occurred during the storage period: mass dehydration; increased pH and specific electric conductivity; and polyphenol degradation. Moreover, substrata presented an interesting content of plant nutrients, in particular potassium, nitrogen, calcium and microelements (magnesium, iron, manganese, zinc and copper). Micro-organisms in the raw olive-mill wastes had values in terms of colonies forming units (CFUs) of 9.4 x 10~(-1)- 1.1 x 10~2per gram of fresh weight, and were mainly yeasts. At milling, yeasts were the prevailing micro-organisms in the substrata, whereas during storage, both in the cold and warm conditions, bacteria seemed to become the most representative micro-organisms (1.8 x 10~2CFUs), probably linked to the increase in pH, detected in the same substrata. Few moulds were present in the different storage conditions. Micro-organisms able to degrade aromatic compounds were also present at different times in the stored substrata. Vegetative and productive parameters,detected in the field experiment, showed no statistically significant differences between the standard mineral fertilizing system and olive-mill waste-based substrata amendments.