Microsoft Word - 8-Agra_12528_traduzir dados autores 1358 Original Article Biosci. J., Uberlandia, v. 30, n. 5, p. 1358-1363, Sept./Oct. 2014 MINERAL NITROGEN IN SOIL LEACHATE AFTER PIG SLURRY APPLICATION NITROGÊNIO MINERAL EM PERCOLADO DE SOLOS APÓS APLICAÇÕES DE DEJETOS LÍQUIDOS DE SUÍNOS Rosele dos SANTOS 1 ; Egon José MEURER 2 ; Verônica SCHMIDT 3 1. Bióloga, Especialista em Licenciamento Ambiental, Mestre em Ciência do Solo, Doutoranda do Programa de Pós-Graduação em Ciência do Solo, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul – UFRGS, Porto Alegre, RS, Brasil. rosele.santos@ymail.com; 2. Professor Associado do Departamento de Solos - UFRGS. Bolsista do CNPq, Porto Alegre, RS, Brasil; 3. Professora Associada do Departamento de Ciências Veterinárias – UFRGS. Bolsista do CNPq, Porto Alegre, RS, Brasil. ABSTRACT: Pig slurry is used as a fertilizer in agricultural soil. The intensification of swine breeding, along with high concentration of animals in small properties, generates great volumes of manure. Pig slurry has high nitrate content, which may contaminate surface and subsurface waters. This study aims to evaluate the environmental impact of pig slurry application in Ultisol and Alfisol samples. For this purpose, pig slurry doses obtained from distinct production systems (farrowing and finishing units) were applied in the following amounts: 0 m3.ha-1 (Control Treatment), 75 m3.ha-1 (T2), 150 m3.ha-1 (T3) and 300 m3.ha-1 (T4). Results showed presence of N-NO3 - + N-NO2 - in Alfisol and Ultisol leachates, and the pig slurry originated from farrowing units showed lower concentration of N-NO3 - + N-NO2 - for both soil leachates. The higher concentration of N-NO3 -+ N-NO2 - in the leachate for both soils was at 19 days after the pig slurry application. Before using pig slurry as a fertilizer it is mandatory to establish criteria for the elaboration of management and provision strategies, in order to reduce environmental and health impacts. KEYWORDS: Concentration. Environmental. Health impacts. INTRODUCTION The worry about environment preservation, especially regarding water quality, has been covered in international meetings, in which agriculture is pointed as a significant source of the contamination, along with animal production. It may contribute for water contamination in the following ways: through surface drainage after application of pig slurry in fields, leaching of compounds resulted from excessive applications, or leakage in storage tanks with inappropriate covering (BASSO, 2003). Normally nitrogen is the element with higher concentration in pig slurry, and a potential environmental contaminant. Among all existing elements in the soil-plant-atmosphere system, nitrogen stands out due to the numbers of biochemical transformations in soil (MOREIRA; SIQUEIRA, 2006). Usually pig slurry application occurs before sowing, during the initial phase of development, and during plant growth, initial phase nitrogen demand is low. The speed of nitrification of slurry ammonium (NH4 +) by specific microorganisms, after the application, determines the amount of nitrate (NO3 -) in soil. With high nitrification rates, the NO3 - concentration rapidly increases, and such increase may occur when nitrogen demand in cultures is low. With intense precipitation, NO3 - leaching may occur, since it is water soluble and has low binding with soil colloids (WHITEWHEAD, 1995), contributing to the contamination of surface and subsurface waters. In Europe, in 1987, when was established the concept of soil multifunctionality, the Netherlands Ministry of Housing, Spatial Planning and the Environment (VROM) published, in 1994, a proposal for the creation of soil and ground water quality index values. This was the reference used for creating the values determined by CETESB (2005), CONAMA (357/2005 Resolution) and CONAMA (420/2009 Resolution), which are Environmental Protection Agencies from São Paulo and Brazil, respectively. The use of international standards may lead to inadequate evaluations, since there are climate, technological, and pedological differences for each country, which justify the development of exclusive lists that represent local environment characteristics. Considering the importance of the aforementioned data, this study presupposes that pig slurry application in soil increases the concentration of mineral nitrogen in leachates, which may result in the contamination of surface and subsurface waters, leading to environmental and health impact. Thus, this study aims to quantify the amount of NO3 - + NO2 - found in Alfisol and Ultisol leachates at 36 hours, 19 and 33 days after the application of pig slurry, which was obtained from two pig production systems (farrowing and finishing units) 1359 Mineral nitrogen in soil SANTOS, R.; MEURER, E. J.; SCHMIDT, V. Biosci. J., Uberlandia, v. 30, n. 5, p. 1358-1363, Sept./Oct. 2014 MATERIAL AND METHODS Sampling Samples of surface layers (0-20 cm) obtained from Ultisol, (sandstone substrate) and Alfisol (basaltic substrate) were used, both registered by the Sistema Brasileiro de Classificação de Solo (EMBRAPA, 2006). This was the first such materials were collected in the area. The soil was selected according to substantial differences in organic matter and clay content, and cation exchange capacity (CEC). The samples were collected using a cutting shovel and then stored in 50kg plastic bags. After that, the soil samples were air-dried and sieved in a 4 mm sieve. The chemical and physical characteristics of soil were determined according to Tedesco et al. (1995), as shown in Table 1. Table 1. Chemical and physical characteristics of the soil used in the experiment Soil Layer (cm) Clay pH MOS CECpH 7,0 Zn Cu Mn P TotalN g.kg-1 H2O g.kg -1 cmolc.dm -3 -------- mg.dm-3 --------- g.kg-1 Alfisol 0-20 470 5,5 26 10,6 5,3 7,1 78 5,9 1,48 20-40 390 5,5 19 9,5 5,4 6,6 55 2,9 1,24 Ultisol 0-20 140 4,6 8 5,4 0,9 8,9 21 1,4 0,72 20-40 140 4,4 5 6,2 0,4 1,4 16 0,9 0,64 Experiment installation The experiment was installed in vessels made of 250mm diameter and 600mm height PVC tubes. The soil samples were separated inside the vessels using 2mm silk screen and 8 µ m filter paper between the 0-20cm and 21-40cm layers. The relative humidity for the soil samples of each experimental unit was kept at 80% of field capacity. Relative humidity control was carried out through weekly measurement and compensation of weight (compared to initial values) by addition of sterile distilled water. Pig slurry samples gathering and characterization The samples from both production systems (farrowing and finishing units) were collected in pig farms, at the same day. The anaerobic ponds were not covered and the pig slurry was homogenized before the collection of samples using wooden rods. The collection was carried out using a receptacle tied to a nylon string, both previously disinfected, which was thrown into the pond, immersed, and retrieved, resulting in a sample composed from two collections. The material was stored in disinfected plastic flasks and kept under refrigeration (approximately 4 ºC). Pig slurry is a mixture of urine, faeces, ration remains, and excess water from drinking fountains and washing of the pigsties where the animals are raised (2.000 individuals in farrowing units and 500 individuals in finishing units). The chemical and physical characteristics of soil were determined as described by Tedesco et al. (1995) and shown in Table 2. Table 2. Chemical and physical characteristics of the pig slurry used in the experiment Characteristics Pig Slurry Origin Finishing Farrowing Humidity % 98,6 99,6 pH 7,9 7,9 Density, kg.m-3 986 939 N, mg.L-1 2250 457 P, mg.L-1 2596 125 Mn, mg.L-1 35 3,9 Cu, mg.L-1 72 12 Zn, mg.L-1 63 33 Organic C, g.L-1 16 1,4 1360 Mineral nitrogen in soil SANTOS, R.; MEURER, E. J.; SCHMIDT, V. Biosci. J., Uberlandia, v. 30, n. 5, p. 1358-1363, Sept./Oct. 2014 Treatment application and leachate gathering The experiment was conducted using full factorial design method, in triplicate. The pig slurry was applied in the surface without incorporation. Each dosage was applied three times in a 14 month period, with intervals of 60 to 80 days between them. In the end the dosage of pig slurry applied was: Control treatment (T1), 75 m3.ha-1 (T2), 150 m3.ha-1 (T3) e 300 m3.ha-1 (T4), respectively. Pig slurry dosage was applied in small aliquots in order to avoid flooding the soil in experimental units. Leachate collection for analysis of mineral N and determination of N-NO3 - + N-NO2 - Leachate collection was conducted in three times: 36 hours, 19 and 33 days after the third application of pig slurry doses. By the date of the collection it was applied 30 mL of sterile distilled water in each vessel, until it was obtained approximately 150 mL of leachate. The water used for obtaining leachate from vessels was sterilized in an autoclave for 25 minutes at 120°C, and the base of the vessels was disinfected with hypochlorite 3% and alcohol 75%. Leachate collection was carried out using disposable plastic receptacles, sterile syringes and surgical gloves. The analysis of mineral N used 20 mL aliquot collected from the leachate using sterile syringes. The content was stored in digestion flasks and immediately frozen. Mineral nitrogen concentrations were obtained by adding 0.2g magnesium oxide (MgO) in the aliquots for the determination of ammonium content (N-NH4), using a semi-micro Kjeldahl distillation apparatus. Afterwards, in the same aliquot, it was added 0.2 g of Devarda’s alloy for determination of nitrate- nitrite (N-NO3 -+ N-NO2 -). The sample’s distillate was evaluated using boric acid indicator and then subjected to titration with 0.0025 mol L-1 acid sulfuric solution (Tedesco et al., 1995). Determining pH and Statistical Analysis pH determination was carried out for all leachate samples, right after collection, using a potentiometer (Digimed, DM -2) with glass electrode (Ag/AgCl). The ASSISTAT 7.5 beta (2008) software was used in the statistical analysis, with analysis of variance using the F test, and results compared through Tukey test at 5%. RESULTS AND DISCUSSION Soil versus dose interaction was significant (p<0,05), which indicates that manure increase in Alfisol significantly raised nitrate content in the leachate 36 hours after the application of manure, as observed when comparing to control treatment without manure application. In this soil doses equivalent to 75 and 150 m3 per hectare resulted in similar nitrate content in soil; the highest dose showed higher nitrate content in the leachate, which was 15.16 mg.L-1 (Table 3). Unexpectedly, nitrate content in Ultisol for control treatment was higher than other treatments. Nitrate content for this soil in leachate was similar for 75, 150 and 300 doses, with no statistical difference between them (Table 3). Table 3. Averages for soil versus dose interaction for nitrate content (mg.L-1) in the leachate of both soils, 36 hours after pig slurry application. Soil Pig Slurry Dose Applied 0 75 150 300 ---------------------------- m3.ha-1 ---------------------------- Alfisol 7.71 bC 12.17 aB 13.32 aAB 15.16 aA Ultisol 16.83 aA 11.98 aB 12.09 aB 12.64 bB DMS for columns = 1.88 (lowercase); DMS for lines = 2.50 (uppercase) The control treatment (T1) for leachates collected 36 hours after the application of pig slurry doses showed the lowest concentration of N-NO3-+ N-NO2-, with 8.26 mg.L-1, same value for both soils (Table 4). Alternatively, the experimental unit added with 100 m3.ha-1 of pig slurry from finishing units showed higher results, 15.16 mg.L-1 of N-NO3 -+ N- NO2 -, as shown in the Table 4. N-NO3 -+ N-NO2 - values found in the leachate for all treatments (T2, T3 and T4) were higher than the maximum value allowed by current legislation (CONAMA 357 resolution). It that enforces water bodies classification and environmental guidelines for the application of the resolution, and also establishes conditions and patterns for effluents and other measures and establishes maximum values of 10 mg.L-1 for N-NO3 - , and 1 mg.L-1 N-NO2 -. 1361 Mineral nitrogen in soil SANTOS, R.; MEURER, E. J.; SCHMIDT, V. Biosci. J., Uberlandia, v. 30, n. 5, p. 1358-1363, Sept./Oct. 2014 Table 4. Concentration of N-NO3 -+ N-NO2 - in Alfisol leachate 36 hours after pig slurry application Treatments Pig Slurry Origin Finishing Farrowing ---------------------------- mg.L-1 ---------------------------- Control Treatment 8.26 cA 8.26 bA T2 - 75 m³ 11.51 bcB 14.57 aA T3 – 150 m³ 14.84 abA 11.80 abB T4 - 300 m³ 16.24 aA 14.09 aA DMS (Tukey 5%) for columns = 3.60 (lowercase); DMS (Tukey 5%) for lines = 2.67 (capital letter) The pH values for collected leachates in Ultisol experimental units showed very low results, with average pH of 3.79 for units that received pig slurry from farrowing, and 3.64 for units that received pig slurry from finishing. pH values for leachates collected in Alfisol experimental units were between 5.74 (farrowing) and 5.77 (finishing). These pH values are very close to the values obtained for the water used in the experiment, which were 5.89. After an eight-hour monitoring procedure, Gomes et al. (2004) showed that nitrification rates from nitrogen (total N) are increasingly higher for samples that showed a slight pH increase. The authors showed that the monitored sample increase was higher than 100% in comparison to the initial nitrate concentration. Basso (2003) observed that higher concentrations of N-NO3- in the soil solution occurred in the initial stages of oats’ development, in which nitrogen demand remained low, since evaluations at 102, 121, and 127 days after application did not showed N-NO3 in the solution. The author also calls the attention to the occurrence of rainfall right after pig slurry application, since NO3 - is water soluble and might follow the waterflow into the soil, leading to irreversible damages to subsurface water resources. The leachate collected at 19 days after the application of pig slurry showed the highest accumulated concentration of N-NO3-+ N-NO2-, a difference higher than 25.53% when compared to concentrations observed for Alfisol. Alfisol showed higher aerobic activity (nitrification), a process that might have been compromised in Ultisol, resulting in lower concentrations of free N-NO3 -+ N-NO2 - in the solution (Table 5). Table 5. Accumulated concentration of N-NO3 -+ N-NO2 - in leachate for interaction: time after the pig slurry application x Soil Treatment Time after pig slurry application 36 hours 19 days 33 days ------------------------------------- mg L-¹ ---------------------------------- Ultisol 12.45 bA 16.41 aA 10.54 cA Alfisol 12.70 bA 15.10 aB 7.86 cB DMS (Tukey 5%) for lines = 1.22 (lowercase); DMS (Tukey 5%) for lines = 1.02 (capital letter) The application of pig slurry as fertilizer may favor N2O emission, since it stimulates both nitrification and denitrification (BASSO, 2003). These processes are greatly responsible for N2O production, although it is not the main product (GIACOMINI, 2005). N2O is a potential pollutant (GIACOMINI, 2005; MOREIRA; SIQUEIRA, 2006), as it reacts with O3 in the stratosphere, affecting the ozone layer (DENDOOVEN et al., 1998; CHANTIGNY et al., 2004), besides leading to the formation of HNO3 an acid rain component (CHANTIGNY et al.; 2004). Nitrogen in ammonia form is susceptible to loss by ammonia volatilization, either in pig slurry storage sites or after field application (PORT, 2002). Thus, after pig slurry application, the availability of N in soil is mainly conditioned to ammonia fraction. Besides being conditioned to loss by volatilization, the ammonia is also susceptible to nitrification and immobilization (GIACOMINI, 2005). Considering a larger scale, like a watershed, the management of pig slurry towards the reduction of nitrogen impact over water quality demands a holistic approach (HEATHWAITE et al., 2000). In the last decades, many of the impacts caused by phosphorus cited in international literature are related to the focus given on nitrogen in the past, which was justified by the high solubility of the nitrate, while other elements, like phosphorus, were not considered potential pollutants. 1362 Mineral nitrogen in soil SANTOS, R.; MEURER, E. J.; SCHMIDT, V. Biosci. J., Uberlandia, v. 30, n. 5, p. 1358-1363, Sept./Oct. 2014 Regarding the use of pig slurry as a fertilizer, the major technical and scientific challenge is to elaborate criteria for evaluating the susceptibility of natural resources to contamination, and then define management and provision strategies, in order to reduce environmental and health impacts. When nitrate is converted into nitrite in the human body, the results are two hazardous chemical reactions: induction of methemoglobinemia (Blue baby syndrome), specially in newborns, and potential formation of nitrosamides and nitrosamines (USEPA, 1989). High contents of NO3 - in soil can also result in accumulated N form in the plant tissue, compromising the quality of plants for consume by humans and animals (L’HIRONDEL; L’HIRONDEL, 2002). There is strong evidence of relations between nitrate and nitrite exposition in humans and risk of cancer (WHO, 2004). CONCLUSIONS The evaluation of Alfisol and Ultisol leachates showed that N-NO3 -+ N-NO2 - was detected, as a result from the application of pig slurry in the surface. The manure from the farrowing system showed lower concentrations of N-NO3 -+ N-NO2 - for both soils. The higher concentration of N-NO3 -+ N- NO2 - in the leachate of both soils was at 19 days after the pig slurry application. N-NO3-+ N-NO2 values found in the leachate for all treatments (T2, T3 and T4) were higher than the maximum value allowed by current legislation. RESUMO: Os dejetos líquidos de suínos (DLS) são utilizados como fertilizante em solos agrícolas. A intensificação de criações de suínos com alta concentração de animais em pequenas propriedades tem gerado grande volume de dejetos. Os DLS podem conter altos teores de nitrato, podendo contaminar águas superficiais e subsuperficiais. Este estudo foi realizado para avaliar o impacto ambiental resultante da aplicação de DLS em amostras de um Argissolo Vermelho Distrófico e de um Nitossolo Vermelho Distrófico. Para tal, aplicaram-se doses equivalentes a 0 (Testemunha), 25 (T2), 50 (T3) e 100 (T4) m3.ha-1 de dejetos líquidos de suínos provenientes de dois sistemas de criação denominados de “creche” e “terminação”. Foi detectada a presença de N-NO3 - + N-NO2 - no percolado do Nitossolo e do Argissolo; o dejeto líquido proveniente do sistema de criação “creche” resultou em menores concentrações de N-NO3 - + N-NO2 - no percolado de ambos os solos. A maior concentração de N-NO3 - + N-NO2 - no percolado ocorreu aos 19 dias após a aplicação dos DLS. Para a utilização dos DLS como fertilizante há necessidade que se estabeleçam critérios adequados para definir estratégias de seu manejo e disposição para reduzir seu impacto no ambiente e à saúde. PALAVRAS CHAVE: Concentração. Meio ambiente. Impacto à saúde. REFERENCES ASSISTAT 7,5 beta. 2008. Desenvolvido pelo professor Dr. Francisco de Assis Santos e Silva, DEAG-CTRN- UFCG, Campina Grande/PB-Brasil BASSO, C. J. Perdas de nitrogênio e fósforo com aplicação no solo de dejetos líquidos de suínos. 2003. 125 f. Tese (Doutorado em Agronomia). Universidade Federal de Santa Maria, Santa Maria/RS. CETESB – COMPANHIA DE TECNOLOGIA DE SANEAMENTO AMBIENTAL, DECISÃO DE DIRETORIA Nº 195-2005- Dispõe sobre a aprovação dos Valores Orientadores para Solos e Águas Subterrâneas no Estado de São Paulo – 2005, em substituição aos Valores Orientadores de 2001, e dá outras providências. 23 de nov. de 2005. CHANTIGNY, M. H. et al. Dynamics of pig slurry nitrogen in soil and plant as determined with 15N. Soil Science Society of America Journal, v. 68, p. 637-643, 2004. CONAMA. Conselho Nacional do Meio Ambiente - Resolução Nº 357, que dispõe sobre a classificação dos corpos de água e diretrizes ambientais para o seu enquadramento, bem como estabelece as condições e padrões de lançamento de efluentes, e dá outras providências. 17 de mar. de 2005 1363 Mineral nitrogen in soil SANTOS, R.; MEURER, E. J.; SCHMIDT, V. Biosci. J., Uberlandia, v. 30, n. 5, p. 1358-1363, Sept./Oct. 2014 CONAMA. Conselho Nacional do Meio Ambiente - Resolução Nº 420, que dispõe sobre critérios e valores orientadores de qualidade do solo quanto à presença de substâncias químicas e estabelece diretrizes para o gerenciamento ambiental de áreas contaminadas por essas substâncias em decorrência de atividades antrópicas. 28 de dez. de 2009. DENDOOVEN, L. et al. Injection of pig slurry and its effects on dynamics of nitrogen and carbon in a loamy soil under laboratory conditions. 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