Biomass and biomass-derived waste are important renewable energy sources which plays a vital role in greenhouse gas reduction from fossil fuel.  Biomass can be degraded in a process known as anaerobic digestion (AD) to produce biogas. Biogas is a mixture of methane and carbon dioxide which is utilized as a renewable source of energy. This project was based on the investigation of AD process in Nordvästra Skånes Renhållnings AB (NSR) a biogas facility in Helsingborg Sweden. A lab simulation of NSR digesters was conducted to evaluate the effects of swine manure on AD using two continuously stirred tank reactors (CSTR) R1 (control) and R2 with a working volume of 4L for 21 weeks. The study was divided into 4 periods and the investigation was carried out by increasing the organic loading rate (OLR) step wise from 2.5 to 3.6 gVSL-1day-1. To assess the effects of swine manure, the performance and stability of the reactors were monitored by collecting data from process parameters. These process parameters included biogas production, pH, volatile fatty acids, methane yield, methane content and organic solids (total and volatile solids). Increase in OLR resulted in increase biogas production in both reactors, however R2 with additional swine manure (15%) produced more biogas than R1. Methane yield was fairly stable during the experiment and had a similar trend in both reactors, but however R2 had a slightly higher average yield (730±60 mLCH4 gVS-1) than R1 (690±60 mLCH4 gVS-1) during the entire experiment. Increase OLR resulted in increase VFA in period 2; R2 with additional swine manure had a lower peak VFA concentration of 25 mM as compared to 33mM in R1.  The characteristics of NSR substrate mix and swine manure provided a good buffering system (stable pH), and reactors were still running stably at 3.6 gVSL-1day-1. Furthermore swine manure was investigated to contain macro-nutrients and trace metals which might have enhanced the AD process in R2 containing more Co, Zn, Ni and Mo than R1. Since this investigation was a simulation, the waste mix used at NSR contained 7% swine manure, this made it difficult to give clearer conclusions about the effects of co-digestion of swine manure on the biogas process since the control (R1) had 7% swine manure. Keywords: Anaerobic digestion, co-digestion, swine manure, substrate mix, organic loading rate, biogas production, methane yield, VFA, process parameters, CSTR.

Swine manure creates much public resentment in Quebec due to nutrient overloading, potential water pollution and odour. Anaerobic digestion is one of the solutions that allows to lessen the odour problem. Anaerobic bacteria in manure produce methane. The latter can be burnt to produce heat and electricity on farms. Moreover, there is a potential for receiving carbon emission reduction credits for the capturing of methane. / Investment analysis was performed to assess the economic feasibility of a potential anaerobic digestion system on a grower-to-finisher hog operation. The study was conducted for a case farm, which had plans to expand from 2000 to 4800 pigs. Greenhouse gas emission reduction credits were incorporated into one of the scenarios. A sensitivity analysis revealed the most important variables which affect the economic feasibility of anaerobic digestion.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais / O objetivo do trabalho foi comparar os atributos químicos do solo, sob dois arranjos de plantio, em linhas simples e duplas de Corymbia citriodora, na profundidade de 0 - 20 cm, e também avaliar a variação nos parâmetros químicos do solo até a profundidade de 60 cm, sob diferentes doses de água residuária de suinocultura (ARS), com arranjo de plantio de Corymbia citriodora realizado em linhas duplas. Foram implantados dois experimentos, na fazenda Bonsucesso, no município de Uberlândia, MG, sendo o primeiro com citriodora em linhas simples, com cinco plantas por parcela, com espaçamento de dois metros entre plantas e 15 metros entre linhas. O segundo experimento foi com citriodora em linhas duplas, com dois metros entre plantas na linha, três metros entre linhas na parcela e 15 metros entre as linhas duplas de citriodora. O delineamento estatístico foi em blocos casualizados. Os tratamentos utilizados foram cinco doses de ARS (0; 200; 400; 600 e 800 m3 ha-1) com cinco repetições. A aplicação das doses de ARS foram parceladas na estação da seca, nos meses de junho, julho e agosto. Para a comparação dos atributos químicos do solo entre os arranjos de plantios, foram coletadas amostras de solo na profundidade de 0 - 20 cm de profundidade. Foi realizada uma análise conjunta dos dados, comparando a análise química do solo. O plantio realizado em linhas duplas de citriodora, proporcionou maiores teores de nutrientes no solo. A aplicação de água residuária de suinocultura elevou os teores de magnésio, potássio e de metais pesados como o cobre e o zinco. Não foi observado 3 1 aumento nos valores de pH do solo, com a aplicação de ARS. A dose de 200 m ha , proporcionou teores adequados para maioria dos nutrientes presentes no solo. Para a avaliação das variações dos atributos químicos do solo, no arranjo de plantio de Corymbia citriodora em linhas duplas, foram coletadas três amostras por parcela, nas profundidades de 0 - 20, 20 - 40 e 40 - 60 cm. Foi utilizado o delineamento em blocos casualizados em 3 -1 arranjo de parcelas subdivididas. A dose de 200 m ha água residuária de suinocultura proporcionou teores adequados no solo para os nutrientes K, Na, Cu e Zn. Houve lixiviação até a profundidade de 60 cm de K, Na, Cu e Zn. Os teores de Mg reduziram no solo com a aplicação de água residuária de suinocultura. A ARS não alterou o pH do solo e os teores de Ca. / The objective of this work was to compare soil chemical attributes under two cropping arrangements in single and double lines of Corymbia citriodora at 0 - 20 cm depth, as well as to evaluate the variation in soil chemical parameters up to the depth of 60 cm, under different swine wastewater (SW) rates, in a silvipastoral system with Corymbia citriodora planting arrangement performed in double lines. Two experiments were implemented, at the Bonsucesso farm, in the municipality of Uberlândia, MG, the first with citriodora in simple lines, with five plants per plot, spacing two meters between plants and 15 meters between rows. The second experiment was with citriodora in double lines, with two meters between plants in the line, three meters between lines in the plot and 15 meters between the double lines of citriodora. The statistical design was in randomized blocks. The treatments used were five rates of SW (0; 200; 400; 600 and 800 m3 ha-1) with five replicates. The application of SW rates were divided in the dry season, in the months of June, July and August. In order to compare soil chemical attributes among planting arrangements, soil samples were collected at depths of 0 - 20 cm depth. A joint analysis of the data was performed, comparing the soil chemical analysis. Planting on double lines of citriodora, provided higher levels of nutrients in the soil. The application of swine wastewater raised the levels of magnesium, potassium and heavy metals such as copper and zinc. No increase in soil pH was observed with the application of SW. The dose of 200 m ha , provided adequate contents for most of the nutrients present in the soil. For the evaluation of variations of soil chemical attributes in the Corymbia citriodora planting arrangement in double rows, three samples per plot were collected at depths of 0 - 20, 20 - 40 and 40 - 60 cm. A randomized complete block design 3 -1 was used in subdivided plot arrangement. The dose of 200 m ha swine wastewater provided adequate soil contents for nutrients K, Na, Cu and Zn. There was leaching to the depth of 60 cm of K, Na, Cu and Zn. The Mg contents reduced in the soil with the application of swine waste water. SW did not change soil pH and Ca content. / Dissertação (Mestrado)

No description available.

Made available in DSpace on 2017-07-10T19:24:56Z (GMT). No. of bitstreams: 1 Priscila_texto.pdf: 1440192 bytes, checksum: 020e7fe3fc653232ee8db5ae1340c1fb (MD5) Previous issue date: 2011-07-23 / Agriculture is one of the major contributors for the emission of greenhouse gases (GHG), being directly related to global warming. Soil and fertilizer management is the agricultural activity that contributes most to emissions. Considering that the western region of Paraná state has a history of land application of swine wastewater (ARS) for crop fertilization, and that studies of GHG emissions from this activity are scarce in our country, the objective of this research is to quantify the carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emission from ARS and mineral fertilizer (AD) application in soybean culture. The experiment was conducted in drainage lysimeters at the Experimental Center of Agricultural Engineering from Western Paraná State University (UNIOESTE). The static chamber method was used to capture the gases, and CO2 emission was measured by the alkaline method at soybean cycle. At the time of the gas collections, temperature and moisture analyses were performed in all plots. Gas analyses were by gas chromatography, and the alkaline CO2 was quantified by titration method. The experiment was arranged in a 4x2 factorial randomized blocks with three replications. The factors evaluated were ARS at doses of 0, 100, 200 or 300 m³ ha-1, and AD levels absence (A) and presence (P). Interactions between SW and SF factors were tested and performed by ANOVA for statistical analysis of GHG, C-equivalent and alkaline CO2 emission. The significant results were compared by Tukey test at 5% significance level. For the correlations, treatments were tested. The CO2 efflux was significant (p-value < 0.05) mainly for the factor ARS, as the N2O one in most sample days. Treatments with 0 m3 ha-1 showed the lowest effluxes and the largest were recorded in treatments with the highest level of ARS (300P and 300A). For both gases, there was no differentiation on the effluxes in D125 and D128 between treatments. This is due to soybean plants decomposition, which provides carbon (C) and nitrogen (N) for micro-organisms. There was interaction (p-value> 0.05) between AD and ARS in D1 for CH4 influx, and AD were significant at D125, in which the CH4 efflux was higher in AD presence. The presence of large amount of N in the ARS does not seem to affect the soil methanotrophic community. The GEE C-equivalent emission was affected by AD and by ARS, with interaction between the factors. There was no significant difference in accumulated CO2 efflux through the alkaline method. The ARS N was probably percolated to deeper soil areas, not affecting the decomposition rate of oat straw. No correlation has been established between the alkaline and chromatographic methods for CO2 efflux recording. It is concluded with this work that ARS land spread is a key factor for the soil GEE increased emissions and that the global warming potential increases with ARS dose applied. / O desenvolvimento do setor agropecuário está diretamente relacionado ao aquecimento global e é grande contribuinte na emissão de gases de efeito estufa (GEE). As atividades agrícolas que mais contribuem para essas emissões são o manejo do solo e o uso de fertilizantes. Sabendo que a região oeste do Paraná possui histórico de aplicação de água residuária da suinocultura (ARS) no solo, aplicada para a fertilização de grandes culturas, e que estudos sobre a emissão de GEE, a partir dessa atividade, são escassos no país, objetivou-se com este trabalho quantificar a emissão de dióxido de carbono (CO2), metano (CH4) e óxido nitroso (N2O), oriundos da aplicação de ARS e fertilizante mineral (AD) na cultura da soja. O experimento foi conduzido no Núcleo Experimental de Engenharia Agrícola NEEA da UNIOESTE em LATOSSOLO com histórico de cinco anos de aplicação de ARS. A captura dos gases se deu pelo método da câmara estática e a emissão de CO2 foi quantificada pelo método alcalino no ciclo da soja. Juntamente com a coleta dos gases, foram registradas a temperatura e a umidade do solo em todas as parcelas em estudo. As análises dos gases foram feitas por cromatografia gasosa e o CO2 do método alcalino foi quantificado por titulometria. O experimento foi em arranjo fatorial 4 x 2 em blocos ao acaso com 3 repetições. Os fatores avaliados foram ARS nos níveis 0, 100, 200 ou 300 m³ ha-1, e AD nos níveis ausência (A) e presença (P). Para a análise estatística da emissão de GEE, C-equivalente e CO2 por captura alcalina testou-se a interação entre os fatores por meio da ANOVA. Os resultados significativos foram comparados pelo teste de Tukey a 5% de significância. Para as correlações testaram-se os diferentes tratamentos. O efluxo de CO2 foi significativo (p-value<0,05) principalmente para o fator ARS, assim como de N2O na maioria dos dias amostrados, em que os tratamentos com 0 m3 ha-1 de ARS demonstraram os menores efluxos. Os maiores efluxos foram registrados nos tratamentos com o maior nível de ARS (300A e 300P). Para ambos os gases, não houve diferenciação do efluxo entre os tratamentos em D125 e D128. Tal fato é devido à decomposição das plantas de soja, que fornece carbono (C) e nitrogênio (N) aos microrganismos. Houve interação (p-value>0,05) entre AD e ARS em D1 para os fluxos de CH4; em D125 foram significativos para AD, em que o fluxo de CH4 foi maior na presença de AD. A presença de grande quantidade de N presente na ARS parece não afetar a comunidade metanotrófica do solo. A emissão de GEE em C-equivalente foi afetada tanto pela fertilização mineral quanto pela aplicação de ARS, apresentando interação entre os fatores. Não houve diferença significativa para a emissão de CO2 acumulado por meio do método alcalino. O N presente na ARS, provavelmente, foi percolado para zonas mais profundas do solo, não afetando as taxas de decomposição da palha de aveia. Não foi estabelecida correlação entre os métodos alcalino e cromatográfico para registro da emissão de CO2. Concluiu-se neste trabalho que a aplicação da ARS é um fator chave para o aumento da emissão de GEE pelo solo e que o potencial de aquecimento global é maior quando se aplica ARS no solo.

Made available in DSpace on 2017-05-12T14:48:18Z (GMT). No. of bitstreams: 1 Priscila_texto.pdf: 1440192 bytes, checksum: 020e7fe3fc653232ee8db5ae1340c1fb (MD5) Previous issue date: 2011-07-23 / Agriculture is one of the major contributors for the emission of greenhouse gases (GHG), being directly related to global warming. Soil and fertilizer management is the agricultural activity that contributes most to emissions. Considering that the western region of Paraná state has a history of land application of swine wastewater (ARS) for crop fertilization, and that studies of GHG emissions from this activity are scarce in our country, the objective of this research is to quantify the carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emission from ARS and mineral fertilizer (AD) application in soybean culture. The experiment was conducted in drainage lysimeters at the Experimental Center of Agricultural Engineering from Western Paraná State University (UNIOESTE). The static chamber method was used to capture the gases, and CO2 emission was measured by the alkaline method at soybean cycle. At the time of the gas collections, temperature and moisture analyses were performed in all plots. Gas analyses were by gas chromatography, and the alkaline CO2 was quantified by titration method. The experiment was arranged in a 4x2 factorial randomized blocks with three replications. The factors evaluated were ARS at doses of 0, 100, 200 or 300 m³ ha-1, and AD levels absence (A) and presence (P). Interactions between SW and SF factors were tested and performed by ANOVA for statistical analysis of GHG, C-equivalent and alkaline CO2 emission. The significant results were compared by Tukey test at 5% significance level. For the correlations, treatments were tested. The CO2 efflux was significant (p-value < 0.05) mainly for the factor ARS, as the N2O one in most sample days. Treatments with 0 m3 ha-1 showed the lowest effluxes and the largest were recorded in treatments with the highest level of ARS (300P and 300A). For both gases, there was no differentiation on the effluxes in D125 and D128 between treatments. This is due to soybean plants decomposition, which provides carbon (C) and nitrogen (N) for micro-organisms. There was interaction (p-value> 0.05) between AD and ARS in D1 for CH4 influx, and AD were significant at D125, in which the CH4 efflux was higher in AD presence. The presence of large amount of N in the ARS does not seem to affect the soil methanotrophic community. The GEE C-equivalent emission was affected by AD and by ARS, with interaction between the factors. There was no significant difference in accumulated CO2 efflux through the alkaline method. The ARS N was probably percolated to deeper soil areas, not affecting the decomposition rate of oat straw. No correlation has been established between the alkaline and chromatographic methods for CO2 efflux recording. It is concluded with this work that ARS land spread is a key factor for the soil GEE increased emissions and that the global warming potential increases with ARS dose applied. / O desenvolvimento do setor agropecuário está diretamente relacionado ao aquecimento global e é grande contribuinte na emissão de gases de efeito estufa (GEE). As atividades agrícolas que mais contribuem para essas emissões são o manejo do solo e o uso de fertilizantes. Sabendo que a região oeste do Paraná possui histórico de aplicação de água residuária da suinocultura (ARS) no solo, aplicada para a fertilização de grandes culturas, e que estudos sobre a emissão de GEE, a partir dessa atividade, são escassos no país, objetivou-se com este trabalho quantificar a emissão de dióxido de carbono (CO2), metano (CH4) e óxido nitroso (N2O), oriundos da aplicação de ARS e fertilizante mineral (AD) na cultura da soja. O experimento foi conduzido no Núcleo Experimental de Engenharia Agrícola NEEA da UNIOESTE em LATOSSOLO com histórico de cinco anos de aplicação de ARS. A captura dos gases se deu pelo método da câmara estática e a emissão de CO2 foi quantificada pelo método alcalino no ciclo da soja. Juntamente com a coleta dos gases, foram registradas a temperatura e a umidade do solo em todas as parcelas em estudo. As análises dos gases foram feitas por cromatografia gasosa e o CO2 do método alcalino foi quantificado por titulometria. O experimento foi em arranjo fatorial 4 x 2 em blocos ao acaso com 3 repetições. Os fatores avaliados foram ARS nos níveis 0, 100, 200 ou 300 m³ ha-1, e AD nos níveis ausência (A) e presença (P). Para a análise estatística da emissão de GEE, C-equivalente e CO2 por captura alcalina testou-se a interação entre os fatores por meio da ANOVA. Os resultados significativos foram comparados pelo teste de Tukey a 5% de significância. Para as correlações testaram-se os diferentes tratamentos. O efluxo de CO2 foi significativo (p-value<0,05) principalmente para o fator ARS, assim como de N2O na maioria dos dias amostrados, em que os tratamentos com 0 m3 ha-1 de ARS demonstraram os menores efluxos. Os maiores efluxos foram registrados nos tratamentos com o maior nível de ARS (300A e 300P). Para ambos os gases, não houve diferenciação do efluxo entre os tratamentos em D125 e D128. Tal fato é devido à decomposição das plantas de soja, que fornece carbono (C) e nitrogênio (N) aos microrganismos. Houve interação (p-value>0,05) entre AD e ARS em D1 para os fluxos de CH4; em D125 foram significativos para AD, em que o fluxo de CH4 foi maior na presença de AD. A presença de grande quantidade de N presente na ARS parece não afetar a comunidade metanotrófica do solo. A emissão de GEE em C-equivalente foi afetada tanto pela fertilização mineral quanto pela aplicação de ARS, apresentando interação entre os fatores. Não houve diferença significativa para a emissão de CO2 acumulado por meio do método alcalino. O N presente na ARS, provavelmente, foi percolado para zonas mais profundas do solo, não afetando as taxas de decomposição da palha de aveia. Não foi estabelecida correlação entre os métodos alcalino e cromatográfico para registro da emissão de CO2. Concluiu-se neste trabalho que a aplicação da ARS é um fator chave para o aumento da emissão de GEE pelo solo e que o potencial de aquecimento global é maior quando se aplica ARS no solo.

No description available.

A study was initiated in 1989 to examine the effects of applying excess liquid hog manure with mineral fertilizers to corn and forage crops. Manure was applied yearly at twice the recommended level either in the spring, fall or a combination of both spring and fall applications. Mineral fertilizers were applied at recommended levels to plots receiving only mineral fertilizers and to manure treatment plots. Two control plots received no fertilizers. / During the summer of 1999, soil samples were taken at a depth of 0--2 cm and analysed using different phosphorus extractants. Six runoff events were sampled and analysed for different phosphorus fractions. / Strong correlations were found in corn plots between average dissolved reactive phosphorus concentrations in runoff and soil test phosphorus concentrations. Timing of manure application had a significant impact on both soil and runoff phosphorus concentrations. Runoff from forage plots had significantly higher concentrations of dissolved phosphorus, but phosphorus loads were greater from corn plots due to higher runoff volumes. Corn plots released significantly higher particulate phosphorus concentrations than forage plots because of higher sediment loads in runoff from corn plots.

A study was conducted to test the effects that different high fibre sources and their varying inclusion levels had on the characteristics of the excreta (faeces, urine and the slurry), and on odour from the slurry of growing pigs. Faeces and urine characteristics were tested from 52 pigs fed rations containing grass hay (GH), lucerne hay (LH), maize cobs (MC), maize stover (MS) and sunflower husk (SH) diets at inclusion levels up to 400 g/kg as fed basis. Faecal output, faecal consistency and nitrogen were influenced by fibre type (P <0.01) and inclusion level (P <0.01). Nitrogen content in faeces and urine was also affected by dietary fibre inclusion. Increasing fibre inclusion levelled to a reduction in urinary nitrogen content, indicating nitrogen repartitioning from urine to faeces, thereby minimizing nitrogen volatilization. The slurry from pigs fed on LH, MC and SH at levels up to 160 g/kg was tested for chemical composition and odour offensiveness. The slurry was incubated for 16 days. The pH and nitrogen content varied among fibre types and incubation period (P <0.05). Isobutyrate and butyrate concentrations varied with fibre type and the incubation period tested (P <0.01). Using panellists, the SH containing rations resulted in low odour offensiveness score. Maize cob-containing diets resulted in the largest odour scores, with (mean rank of 2.2 and 4.3 for SH and MC, respectively). To reduce odour offensiveness from piggeries, sunflower husk was recommended as an alternative feed ingredient for growing pigs. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The increase on swine livestock activity demands profitable resources and environmentally sustainable for the treatment, disposal and the residual water reuse. Due to the high wastewater volume, they have a huge pollutant load, among them several metals, that can cause environment impact. This work presents an evaluation of phase separation for Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr and Zn removal in swine manure through the coagulation and flocculation whit synthetic and natural polyelectrolyte. For this proposal, the metals were monitored in the effluent and solid-liquid separation assays (Jar Test) with poliphenolic polymer (Tannin) and polyacrilamide (PAM) applied at different concentration. The optimization was accomplished by the application of factorial design. For the metal determination three mixtures of reagents had been evaluated (nitric acid + perchloric acid, sulfuric acid + hydrogen peroxide and nitric acid + hydrogen peroxide) for samples decomposition of swine manure, the best result for recovery and correlation was found to nitric acid and hydrogen peroxide mixture. After the separation of the liquid fraction, reductions between 68 and 99% were found out in the investigated metal concentrations. Besides that, reductions over 90% for chemical oxygen demand were also observed. A significant influence in turbidity removal only by the tannin utilization was found out. However the PAM application improved directly the flocks generation and influenced the sludge volume reduction. The polyelectrolyte use provided the reduction of metal concentration in the wastewater to adjust to the brazilian legislation for discharging into water bodies or for reuse in irrigation systems. The sludge produced after the solid-liquid separation also showed concentrations of inorganic constituents below of maximum limits claimed by legislation for the agricultural use. / O crescimento da atividade suinícola demanda recursos rentáveis e ambientalmente sustentáveis para o tratamento, disposição e reuso de suas águas residuárias. Além de seu grande volume de efluentes, estes possuem alta carga de poluentes, entre eles diversos metais, danosos ao meio ambiente. Este trabalho apresenta uma avaliação da separação de fases para remoção de Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr e Zn em dejetos de suínos através de coagulação e floculação com polieletrólitos, sintético e natural. Para isso, monitoraram-se os metais no efluente e foram realizados ensaios de separação sólido-líquido (Teste de Jarro) com aplicação de polímero polifenólico natural (tanino) e poliacrilamida (PAM). As otimizações foram realizadas aplicando planejamento fatorial. Para as determinações de metais foram avaliadas decomposições de amostras de dejeto de suíno empregando três misturas de reagentes (ácido nítrico + ácido perclórico, ácido sulfúrico + peróxido de hidrogênio, ácido nítrico + peróxido de hidrogênio), onde os resultados de recuperação e correlação permitiram a escolha da mistura ácido nítrico e peróxido de hidrogênio. Foram observadas reduções entre 68% e 99% nas concentrações dos metais investigados após separação da fração líquida, além de reduções superiores 90% para a demanda química de oxigênio e superiores a 98% para a turbidez. Foi constatada interação na remoção de turbidez somente ao emprego de Tanino, porém a aplicação de PAM melhorou diretamente a formação dos flocos e sedimentação do lodo. Os polieletrólitos proporcionaram a redução da concentração de metais na água residuária, auxiliando no enquadramento das concentrações dos metais investigados à legislação, para descarte em corpos de água receptores ou ao reuso em sistemas de irrigação. O lodo produzido após a separação sólido-líquido apresentou concentrações de constituintes inorgânicos abaixo dos limites máximos exigidos pela legislação para o uso agrícola.