Caracterização físico-hídrica do solo após cultivos fertirrigados com água residuária sanitária tratada

Abstract

The urban and industrial growth has intensified the production of waste in recent years, which in large part of the country has a direct destination to the water bodies causing environmental imbalance and a decrease in water quality. Even after being treated and following the current legislation the treated sewage may also be able to eutrophize the water of the receiving body. Studies are needed that look for alternatives of reuse of the products of the treatment of the sewage in order to destine it in a sustainable and safe way to the environment. The agriculture has proved to be a viable destination and a number of studies are published worldwide with this approach. The objective of this study was to evaluate possible changes in water movement and retention in eutrophic Red Latosol at the end of successive applications of tertiary sanitary wastewater (ART) in maize (Nov/2012 to Feb/13), cotton to nov/13), common bean (Apr to jun/14) and pineapple (Jul/15 to March/17) aiming at the partial supply of nutrients to the plants. All cultivations were conducted in the same area and in the same experimental plots involving 5 treatments of ART (0: clean water and mineral fertilization, 1: 50, 2: 100, 3: 150 and 4: 200% (Table 1), and in the first 3 crops and 0: clean water and mineral fertilization, 1: 100, 2: 200, 3: 300 and 4: 400% of the ART dose limited by the reference Na + element in the pineapple) , with 4 replicates. The field experiment was carried out in Janaúba - MG at the end of the four cycles. It was evaluated the electrical conductivity of the saturated extract (ECes), exchangeable sodium percentage (PST), water dispersed clay (ADA), total water storage availability (DTA) stratified in layers of 0.2 m to 0.8 m depth and basic infiltration velocity (VIB), infiltration velocity at 1.5 h (VI1.5) and hydraulic conductivity (K0) measured at the field surface. In addition, which empirical model was best fitted to the infiltration velocity data collected in the field was 4 determined. A linear decrease of 0.0972 mm h-1 , 0.0997 mm h-1 and 0.0073 cm h-1 , respectively, was observed in the basic infiltration rate, time infiltration rate of 1.5 and conductivity for each mm of waste water increased in the soil, in addition to increasing the percentage of exchangeable sodium up to 0.6m deep. It was determined that for the studied conditions the empirical model of Kostiakov was the most efficient to adjust the data collected in the field and to estimate infiltration velocities. Still with the changes observed, it was verified that there was no impairment of movement and retention of soil water, since the answers of the analysis of the data collected do not exceed limits considered as safe in the literature. Therefore, it is recommended the use of ART in fertigation guided in reference element without risks to the movement and retention of water in the soil.