Swine Manure

The large volumes treatment of waste generated by Brazilian swine production has been the main difficulty faced by this activity. Treatment systems able to reduce the pollution potential of this waste and make its use sustainable in agriculture soils have been searched. The use of treated swine wastes can represent savings of chemical fertilizers and irrigation for crops. However, its use without adequate treatment can cause contamination of the soil-water-plant system, mainly by the presence of pathogenic organisms, excess salts and heavy metals in soil solution, and ion leaching. The aim of this study was to evaluate the effects the agricultural use of swine wastewater treated in an anaerobic biodigester, in winter maize cultivation, considering agronomic and environmental aspects. The effluent was generated in a swine farm with animals in termination phase. This effluent was sieved to remove suspended solids and treated in an anaerobic biodigester, for an average period of 60 days, resulting in treated swine wastewater (WB – swine wastewater treated in biodigester) for agricultural use. The field experiment was performed in an Oxisol, clayey. The experiment was designed in randomized blocks, and the treatments were: T1: control (no water and no fertilizer); T2: mineral fertilization without irrigation; T3: irrigation with WB; T4: irrigation with WB diluted (WBD); T5: mineral fertilization and irrigation with water. The effluents (WB) were characterized before of each irrigation, in order to assess the efficiency of the anaerobic digestion process and also to quantify the nutrients supply to culture. The maize crop was irrigated when necessary, through the assessment of soil water potential, by measurements made in tensiometers. Also, we evaluated the effects of irrigation on soil fertility, crop nutrition, ions movements in the soil by the method
extraction of saturation paste, crop productivity, as well as the nitrogen losses by volatilization were quantified in semi-open chambers installed in the plots with use of swine wastewaters and in control treatment. The
treatment system promoted reduction in values of BOD, COD, total solids, fixed solids, volatile solids, phosphorus, calcium, and total coliforms removal. The losses of nitrogen through volatilization were low and equal to 3.3 and 6.4% for T3 and T4, respectively, indicating it not to be necessary to incorporate the swine wastewater into the soil. Such losses caused no negative effects on nitrogen contents in leaf, which were within the range considered suitable for maize (27.5 to 32.5 g kg-1
). The P contents in leaf were low in all treatments (1.6 to 1.9 g kg-1
) due to the fixing of phosphorus to the oxides of iron and aluminum present in soils under tropical conditions. There was an increase in productivity in treatments irrigated with swine wastewater treated
(T3), equal to 6.7 t ha-1, higher than the average productivity obtained for the São Paulo State of 4.6 t ha-1. Despite the lower supply of nitrogen, the T4 treatment (WBD) showed productivity equal to the treatment with
mineral fertilizer - T2 (4.5 and 4.3 t ha-1 , respectively), demonstrating response to the adequate water supplies and other nutrients. The contents of available potassium were higher in T3 (6.9 mmol
c dm-3 ) than in other treatments studied, this resulted in higher concentrations of ion in soil solution equal to 29.1 mg kg-1 , which
represents 10.9% of the exchangeable K, in the depth of 0-0,20m. There was no nitrate leaching risks, since the ion content in T3 and T4 was lower than those observed for treatments with mineral fertilization (T2 and T5) at both depths studied, which may indicate greater extraction of the element by the plant in treatments with use ofWB and WBD. There was 120% increase in sodium content in the soil solution in the treatment with use ofWB. The treated swine wastewater showed that it has a high potential for agricultural use, which may represent savings to agricultural producers in the use of chemical fertilizers. However, long term studies are necessary to remove Na and K of the swine wastewater, thus, the monitoring of these elements and nitrate in the soil profile
should continue, in order to enable the safe recommendation of this waste to be used in agricultural soils.