Desenvolvimento de substratos orgânicos, com base na vermicompostagem, para produção de mudas de hortaliças em cultivo protegido

Abstract

Organic substrates were developed, using renewable and locally available sources, for vegetable transplant production in expanded polyestirene trays under protected environment. Vermicompost, coming from cow manure, was chosen as a basis for the substrates. Vermicompost physical and nutritional characteristics were improved by the addition of fine charcoal and castorbean cake. The first component is a residue from wood processing, easily found at minimum cost. Castorbean cake supplied by local stores is known to be rich in macronutrients, especially nitrogen. Bioassays in the greenhouse, including vegetable crops of different groups (lettuce, rocket press, eggplant and sugarbeet), demonstrated efficacy of the vermicompost substrates supplemented with fine charcoal and castorbean cake. Based on growth parameters of the transplants, the substrate consisting of vermicompost plus 15% (v/v) of fine charcoal was selected. Fine charcoal was represented by a misture particles held in 3mm and 5mm mesh sieves (equal parts – v/v). Castorbean cake employed for enrichment of that substrate was adequated when added in dosages that varied from 1% to 4%, depending on the vegetable species tested. Such result reflected different levels of tolerance to substrate salinity among these species. It also pointed out to the convenience of specific adjustments in substrates composition for vegetable transplants, as a function of the requirements of each group. Yield of organically grown sugarbeet in the field was increased as influenced by the transplant quality due to the macronutrients content of the organic substrate. This enhancing effect on productivity was intensified by a dress application of castorbean cake during sugarbeet cycle. The research indicated potential of the evaluated substrates as viable options in accordance to the regulatory standards stated by the Brazilian legislation on organic farming.