| dc.description.abstract | The use of swine liquid manure (SLD) as an organic fertilizer in agricultural areas is a
sustainable and profitable way of disposing of this environmental liability. In its composition it
has elements such as phosphorus, nitrogen, copper, zinc, iron and manganese and also organic
matter that are attractive because they are essential macro and micronutrients for the
fertilization of the most diverse cultures. Both phosphorus, copper and zinc, in addition to
nutrients, when applied in excess to the soil, can act as potential contaminants, causing
eutrophication in water bodies and even causing toxicity to plants. Also, when used by
successive DLS applications, they increase their levels available in the soil, sometimes
saturating this environment. In view of this, the present study was carried out in 67 plots of 15
swine farms in the Lajeado Caldeirão watershed, Palmitinho-RS, which aimed to evaluate the
availability levels of phosphorus, copper and zinc in order to verify their agronomic potential,
as well as verifying their contaminating potential, evaluating them based on the Environmental
Critical Limit of Phosphorus (LCA-P) and the Quality Reference Values (QVR) for the pseudototal
copper and zinc contents. As a methodology, field research, collection and sampling of
soil was adopted, analyzed by the Laboratory of Soil Chemical Analysis at the Federal
University of Santa Maria, Frederico Westphalen campus. For sampling of available
phosphorus, the USEPA method (SW846-3050B) was used. The available copper and zinc
contents were extracted using the Mehlich-1 solution and quantified by atomic absorption
spectrophotometry. For pseudo-total copper and zinc contents, the USEPA method (SW846-
3050B) was used. For the leveling of the values, 55 areas with use of DLS (ADS), 5 of native
forest (AMN) and 7 with exclusive use of chemical fertilization (AAQ) were used. As a result,
the supply of DLS for the sum of the plots of each pig unit proved to be insufficient for 93% of
the enterprises. Regarding the agronomic potential of the areas, most ADS and AAQ had high
to very high availability of phosphorus, indicating great agronomic potential. For copper and
zinc, the high levels of availability found in ADS increased loads up to 8.3 and 5.3 times,
respectively, the average levels found in the reference areas (AMN). As for the environmental
limits of the elements and VRQs, 14 plots (20.8%) of the studied areas presented critical levels
in the soil, being above the LCA-P (5), above the VRQ+50% for copper (10) and above the
Prevention Values (PV) for zinc (4). Furthermore, the pseudo-total copper and zinc contents of
most AMNs were found to be above the VRQs established by law. Finally, it was evidenced
that the management with DLS in the study area is optimized, referring to its agronomic
potential, however, it is necessary to monitor the plots that presented critical levels because
they are potential soil and water contaminants, still that the QRQs are below the natural grades of the watershed. | |
