Biological strategy to improve decomposition of organic matter in tilapia pond

Aim The increment of decomposition of organic matter in sediment samples from Nile tilapia farms was evaluated with the introduction of Bacillus subtilis and B. licheniformis bacteria. Methods Sediment samples placed in 18L plastic boxes received single dose inoculum with the following concentrations: 1.21 x 106 CFU g-1 (equivalent to 75 g ha-1), 2.41 x 106 CFU g-1 (equivalent to 150 g ha-1), 4.82 x 106 CFU g-1 (equivalent to 300 g ha-1) and 1.61 x 107 CFU g-1 (equivalent to 1000 g ha-1), in addition to a control treatment with saline solution only. Organic matter content, total organic carbon (TOC) and oxidizable (OOC), total nitrogen (TN), ratios (TOC: N and OOC: N), clay content, pH in water, Shoemaker, McLean, Pratt index (SMP Index), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) contents, potential acidity (H + Al), cation exchange capacity (CEC) at pH 7.0, base saturation (V) and sum of bases (S). Results The values of OM showed significant difference, between the lowest values (treatments 75, 150 and 300 g ha-1) and the highest value, (control treatment). TOC, OOC, NT and their relationships (TOC: N and OOC: N) showed significant differences between the mean values of the control treatment and the other treatments. Conclusions The addition of Bacillus subtilis and B. licheniformis bacteria increased the decomposition rate of organic matter in sediments samples from Nile tilapia farms. Resumo: Objetivo Foi avaliado o incremento da decomposição da matéria orgânica em amostras de sedimento de viveiros de criação de tilápias-do-Nilo com a introdução das bactérias Bacillus subtilis e B. licheniformis. Métodos Amostras de sedimento colocadas em caixas plásticas de 18L, receberam dose única de inóculos com as seguintes concentrações: 1,21 x 106 UFC g-1 (equivalente a 75 g ha-1), 2,41x 106 UFC g-1 (equivalente a 150 g ha-1), 4,82 x 106 UFC g-1 (equivalente a 300 g ha-1) e 1,61x 107 UFC g-1 (equivalente a 1000 g ha-1), além de um tratamento controle, com adição apenas de solução salina. Foram analisados teor de matéria orgânica, teores de carbono orgânico total (COT) e oxidável (COO), nitrogênio total (NT), relações de carbono: nitrogênio (COT:N e COO:N), teor de argila, pH em água, índce Shoemaker, McLean, Pratt (índice SMP), teores de fósforo (P), de potássio (K), de cálcio (Ca) e de magnésio (Mg), acidez potencial (H+Al), capacidade de troca catiônica (CTC) a pH 7,0 e saturação por bases (V). Resultados Os valores de MO apresentaram difer