The efficiency index (EI) refers to the ratio of nutrients mineralized/made available in the soil to the total amount of nutrients added by organic fertilizer. Therefore, understanding the EI is essential for recommendation of organic fertilization. The aim of this study was to evaluate the availability through mineralization and the efficiency index of nitrogen (N), phosphorus (P), and potassium (K) in organic fertilizers produced from cattle manure. The following treatments were evaluated in an incubation experiment under controlled conditions: soil without fertilizer (control); soil + beef cattle manure vermicompost; soil + beef cattle manure/straw compost; soil + beef cattle manure; soil + dairy cattle manure; and soil + vermicompost produced under conditions of high moisture and forced air. Nitrogen and P mineralization and K availability in the soil were evaluated at 0, 7, 14, 28, 56, 112, 224, and 365 days. Nitrogen availability in the soil increased after the bioconversion of cattle manure by composting, whereas phosphorus availability increased by vermicomposting. The average efficiency indices of N, P, and K of the fertilizers produced from cattle manure were 16, 57, and 82 %, respectively. These efficiency indices are lower than the values presented by the Liming and Fertilization Manual for the states of Rio Grande do Sul (RS) and Santa Catarina (SC), Brazil.
organic fertilizers; vermicompost; efficiency index