Concentrações de esgoto doméstico tratado e lâminas de irrigação no cultivo do capim elefante

Abstract

Agricultural use of lower quality water sources, such as sewage of domestic origin, comes up as alternative to increase water supply. The elephant grass is a perennial forage, of high production potential of dry and fresh phytomass, and quite nutritious, can be used as hay, pasture, silage and grassland. The accomplishment of this work had as objective evaluate the viability of elephant grass irrigation with different irrigation blades and concentrations of treated domestic sewage. Two experiments were carried out on the experimental area of the Meteorological Station of the Federal University of Ceará, campus of Pici, in Fortaleza, Ceará. The treated domestic sewage used it came from the sewage treatment station of UFC. For both experiments, the experimental design was that of random blocks, with six treatments and four repetitions, containing ten plants in each plot. The treatments of the first experiment consisted of five application combinations of treated domestic sewage (EDT) and well water (AP): 0% (100% AP), 25% (25% EDT + 75% AP), 50% (50% EDT + 50% AP), 75% (75% EDT + 25% AP), 100% (100% EDT) and a additional treatment irrigated 100% with well water + mineral fertilization (N-P-K). The treatments of the second experiment consisted of five irrigation blades with treated domestic sewage, based on crop evapotranspiration (ETc), and one witness: L1 (50% ETc); L2 (75% ETc); L3 (100% ETc); L4 (125% ETc); L5 (150% ETc); and L0 (100% ETc with well water + mineral fertilization (N-P-K). The variables analyzed in the plant were: the number of leaves; stem diameter; number of tillers; plant height; leaf area; bulk fresh and dried of leaf and stem; productivities of bulk fresh and dried and the macronutrient content in the aerial part. On the ground, were evaluated the contents of phosphor (P), potassium (K), calcium (Ca), magnesium (Mg) and nitrogen (N), besides of pH, electric conductivity (CE), sum of bases (SB), percentage of exchangeable sodium (PST) and cation exchange capacity (CTC). The production of elephant grass irrigated with combinations of well water and treated domestic sewage proved viable as long as there is minimal participation of 50% of EDT. Among the tested irrigation blades with EDT, the highlights were 125 and 150% of the ETc, providing the best responses from culture and equaling the witness treatment. The nutrient content in the plant of elephant grass was positively influenced by the use of treated domestic sewage (EDT) in irrigation, in the combined form with well water or just the EDT.