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

Abstract

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<sup>®</sup>, Organ CAP<sup>®</sup>, Sic Stal<sup>®</sup> and urea (as a control) at the rate of 300 mg N/kg dry soil. Emos CAP<sup>®</sup> is made of cattle and poultry manure, meat, bone meal and dried blood, Organ CAP<sup>®</sup> is a product made of leather and skins, while Sic Stal<sup>®</sup> contains cow and horse manure. During the incubation the concentration of NO<sub>3</sub><sup>–</sup>-N, NH<sub>4</sub><sup>+</sup>-N, microbial biomass and carbon dioxide, nitrous oxide and ammonia emissions were determined. All fertilizers showed a peak of NH<sub>4</sub><sup>+</sup>-N after 7 days from the beginning of the test. The decomposition of Sic Stal<sup>®</sup> caused a rapid rise of CO<sub>2</sub> production associated to the growth of microbial biomass while Emos CAP<sup>®</sup> promoted a release of N<sub>2</sub>O 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<sup>®</sup> and Sic Stal<sup>®</sup> allow a rapid N supply to plants while Organ CAP<sup>®</sup> could be used when the N request of plants is not immediate.