Abstract

SOTOMAYOR, Carolina; MORANDINI, Miguel; SANZANO, Gerardo A.  and  ROJAS QUINTEROS, Hugo C.. Effect of the application of vinasse on chemical and physical properties of the soil. Rev. ind. agric. Tucumán [online]. 2018, vol.95, n.1, pp.27-33. ISSN 1851-3018.

Waste from sugar industry can be converted into by-products of high economic value, such as molasses. This is used in the production of bioethanol, obtaining a liquid residue called vinasse, which is produced in an average ratio of 10 to 15 liters per liter of ethanol produced. Because of its high biological demand for oxygen (BOD), when it is turned over to the watercourses, it consumes dissolved oxygen and causes a high mortality of aquatic flora and fauna. The high content of soluble salts is also important, with relative predominance of potassium (K+). In Tucumán, alternatives for managing this effluent include irrigation in fields where sugarcane is going to be planted as well as in non-productive soils. Since it was necessary to know its impact on the soil, an experiment was carried out under controlled conditions. The objective was to evaluate the effect of the application of different doses of vinasse on physical and chemical properties of a soil in Tucumán and to evaluate the leaching of K+ towards deeper layers of the soil profile. Unaltered soil columns of 60 cm long were used in a completely randomized design. The soil was from Los Zelaya, Leales Department. Five vinasse doses equivalent to 0, 10, 50, 100 and 150 m3 of vinasse per hectare were evaluated with three replicates, trying to simulate the effect of three years of effluent use. Each vinasse application was followed by water irrigation. The leachates were collected and analyzed for pH, salts and soluble potassium. Electrical conductivity, pH, organic matter, exchangeable potassium, bulk density and hydraulic conductivity were analyzed in the soil samples, every 10 cm depth. The results showed significant increases in pH and salinity for the first 30 cm of soil. Exchangeable potassium increased significantly in all studied depths, with an increase of applied doses of vinasse. Organic matter, bulk density and hydraulic conductivity showed no significant differences. Salts and pH in the leachates showed significant increases after the third vinasse application. Soluble potassium increased significantly with higher doses of vinasse. K+ increase did not cause alterations in physical properties of the soil. The increase in the concentration of soluble salts in soils could be considered a risk in sugar cane fields, confirming the need to evaluate this parameter in time and soil depth. Salt leaching to deeper layers and to the water table should also be considered.

Keywords : molasses; bioethanol; pollutant; potassium; leachates.

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