Compostos orgânicos a base de resíduos agrícolas como substrato para produção de mudas de cana-de-açúcar e capim-elefante

Abstract

Brazil is the world's largest producer of sugarcane, which can be used for the production of various products, such as sugar, ethanol, brandy, rapadura and for animal feed. Another species widely used for animal feed is elephant grass, among the cultivars of the species are BRS Kurumi and BRS Capiaçu. Since both species have vegetative propagation, it is possible to use the seedling production system via minitoletes, but this system requires significant amounts of substrate. Based on this, the objective of the work was to determine the potential of three organic compounds in the preparation of substrates for the production of sugarcane and elephant grass seedlings, characterizing them in terms of sanitary aptitude and evaluating agronomic efficiency. The raw materials for the composting process were: Organic compound 1- sugar cane bagasse and straw, sawdust and cattle manure; organic compound 2- sugar cane bagasse and straw, acacia bark and poultry litter; and organic compound 3- sugar cane bagasse and straw, sawdust and tung cake. The compounds were characterized in terms of nutrient content, pH and electrical conductivity (EC) measurements and the presence of pathogens. Subsequently, different proportions of rice husk ash and carbonized rice husk were added to the compounds, resulting in 12 different substrates. For the purpose of comparing results, the commercial substrate Turfa Fértil® was used. The substrates were characterized in terms of physical-water parameters. The agronomic efficiency tests of substrates based on organic compounds were conducted in a greenhouse, located at Embrapa Clima Temperado, located in Pelotas / RS. The seedlings of the species studied were produced from individualized minitoletes of stalks, following the methodology adapted from Landell et al. (2012). The individualization of the blades was carried out with the aid of a double blade guillotine system, separating viable buds, which were planted in tubes (175 cm3) containing the different substrates. For the production of sugarcane seedlings, the genotypes RB867515 and RB966928 were used. The experimental design used was in randomized blocks with four replications and thirteen treatments. The agronomic variables evaluated were percentage of sprouting, number of leaves, diameter of the neck, height of the aerial part, length of the root, fresh and dry mass of the aerial part and dry mass of the root. The results obtained indicated that two of the compounds produced are suitable for use in agriculture according to the maximum limits of pathogenic agents established in the current legislation. The proposed compounds have satisfactory nutrient, pH and EC contents as well as the substrates for the physical-water characteristics, reflected in the development of the seedlings of the studied species, where substrates based on organic compounds have agronomic responses equal to or greater than the commercial substrate, the substrate with 100% organic compost 2 and the substrate with 75% organic compost 2 + 12.5% rice husk ash + 12.5%