Uso de resíduos orgânicos na composição de substratos alternativos para a produção de mudas

Abstract

The use of organic residues as components of substrates allow obtaining alternative materials, easily obtained, constantly available and of low cost, aiding on the minimization of pollution resulting from residue accumulation in the environment. Therefore, this study evaluated the quality of substrates formulated with organic residues on the process of emergence and growth of Brassica oleracea var. acephala and Helianthus annuus L. The experiments were done in the greenhouse of the Instituto de Ciências Agrárias of Universidade Federal de Uberlândia (UFU), in the city of Uberlândia-MG, using multicelled trays, and each experimental unit consisted of twenty four cells. The experimental design was completely randomized. Six treatments, in four replications were used in the experiment with Brassica oleracea var. acephala. The first treatment, considered as the control, consisted of the mixture of the commercial substrate Plantmax® with vermiculite in the proportion 1:1. The other treatments were increasing doses of composted sewage sludge and sugar-cane bagasse (20, 40, 60 or 80%) mixed to the substrate of the control treatment, and the last treatment was 100% compost. Four treatments, in five replications, were evaluated in the Helianthus annuus L. experiment, where increasing doses of the biosolid (20, 40 or 60%) were added to the same control treatment. The evaluations of the emergence process were done every twenty four hours, adopting as emergence criterion the exposition of any seedling part on the substrate surface. Growth was evaluated by measuring the above ground height, the length of the root system and the dry matter mass of both parts. The substrate containing 20% biosolid presented adequate chemical and physical characteristics for sunflower development, although the minimum average time ( t = 3.46 days), the least uncertainty (I = 1.38 bits), the greatest velocity ( v = 0.88 day-1; VE = 7.15 seedlings day-1) and the greatest synchrony (Z = 0.42) of emergence were obtained by the control treatment. Adding the sludge and bagasse organic compost to the substrate, in concentrations above 30%, caused an increase in initial time (ti), average time ( t ) and final time (tf) for collard seedlings emergence, and a linear decrease on the average velocity ( v ) and Maguire s emergence velocity (VE) was observed with the addition of compost to the substrate. It can be concluded that the use of biosolid and the organic compost of sewage sludge and sugar-cane bagasse as substrate components, to a given proportion, is a viable alternative for the re-use of residues.