Avaliação nutricional de compostos orgânicos produzidos a partir de fezes caninas e bovinas com serragem de madeira

Abstract

The use of animal feces in composting processes is common, but canine feces are rarely used, as they can represent a risk of contamination and consequently unusability of the compost. In view of the amount of canine feces generated in urban environments and the inherent risk of the residue, it is important to create solutions for its destination, and composting is a simple and low-cost possibility. The objective was to nutritionally evaluate the quality characteristics of two organic compounds produced from canine feces (CF) with wood sawdust (WS) and bovine feces (BF) with WS, for agricultural use, with regard to the concentration of metals, and macro and micronutrients. The experiment was carried out in the greenhouse of the Center for Studies on Oilseed Plants, Vegetable Oils, Fats and Biofuels (G-Oil), of the Departments of Agricultural Engineering and Agriculture, Federal University of Lavras (UFLA). Six piles were assembled, three with 85% of BF and 15% of WS and other three with 85% of CF and 15% of WS, with a dimension of 1m³ and monitored for 90 days. The windrows were turned and the temperature and humidity were monitored three times a week. The mean temperature of the windrow was determined using a stick thermometer and the monitoring of humidity was empirically carried out by pressing part of the composted material, keeping the humidity between 40% and 60%. After a period of one month, the maturation phase began, which lasted for another two month. After collection, the material was taken to the Wastewater Laboratory and Soil Fertility Laboratory at UFLA, for analysis of macro, micronutrients and metals. The variables analyzed were submitted to Student's t test for independent data with equal variances and a significance level of 5% (0.05 p-value) was adopted as a significant difference. Significant differences were observed in the mean concentrations of calcium (Ca) and zinc (Zn) (P<0.05). The other parameters analyzed were not observed significant differences between the two compounds (P<0.05). With the accomplishment of this study, it was observed that both organic compounds are similar and can be used as organic fertilizer, being necessary the periodic monitoring of metals in the destination soil, mainly Zn. However, the variables analyzed are above the minimum required by Brazilian standards for commercialization as organic fertilizers.