Mineralization dynamics of different commercial organic fertilizers from agro-industry organic waste recycling: an incubation experiment

The mineralization process of different commercial organic fertilizers was investigated in controlled laboratory conditions. The soil was mixed with the following organic fertilizers: Emos CAP®, Organ CAP®, Sic Stal® and urea (as a control) at the rate of 300 mg N/kg dry soil. Emos CAP® is made of cattle and poultry manure, meat, bone meal and dried blood, Organ CAP® is a product made of leather and skins, while Sic Stal® contains cow and horse manure. During the incubation the concentration of NO3--N, NH4+-N, microbial biomass and carbon dioxide, nitrous oxide and ammonia emissions were determined. All fertilizers showed a peak of NH4+-N after 7 days from the beginning of the test. The decomposition of Sic Stal® caused a rapid rise of CO2 production associated to the growth of microbial biomass while Emos CAP® promoted a release of N2O in the first 16 days. In conclusion, all the commercial organic fertilizers tested can be considered fertilizers with a fast release of N, among them Emos CAP® and Sic Stal® allow a rapid N supply to plants while Organ CAP® could be used when the N request of plants is not immediate.