Field application and gas emissions from dairy slurry treated by additives and mechanical separation
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2017
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Um sistema de bovinicultura leiteira intensiva com base em duas culturas forrageiras
anuais foi desenvolvido no Noroeste de Portugal. Este sistema gera anualmente grandes
volumes de chorume e, embora este efluente possa ser utilizado para o fornecimento de
nutrientes às culturas forrageiras praticadas, a disponibilidade de solo é limitada para a sua
reciclagem. Para garantir a sustentabilidade da produção agrícola nesta região, o excesso de
chorume bovino precisa de ser tratado e/ou transportado para explorações com necessidades
acrescidas de nutrientes.
O objetivo geral desta tese foi avaliar os impactos ambientais e agronómicos no sistema
de duas culturas forrageiras anuais de milho / aveia, decorrentes do tratamento de chorume por
separação mecânica de sólidos e pela aplicação de aditivos, a fim de definir as práticas que mais
contribuam para a redução das perdas de nutrientes e, simultaneamente, garantam o aumento
da eficiência e do rendimento das culturas e o seu valor nutritivo.
Esta tese está organizada em 5 capítulos. O Capítulo 1 apresenta o state-of-the-art
relativamente ao ciclo do azoto em sistemas leiteiros, emissões gasosas provenientes da
agricultura, mecanismos e fatores que controlam a volatilização de amoníaco (NH3) e as
emissões de metano (CH4) e óxido nitroso (N2O) durante o armazenamento de chorume e após
a sua aplicação ao solo. Neste capítulo, dá-se ainda ênfase às estratégias de mitigação para
minimizar as emissões desses gases.
No Capítulo 2 descreve-se um ensaio onde foi avaliado o impacto do tratamento do
chorume por aditivos biológicos (EU 200®, Bio-buster® (BB) e JASS®) e de um aditivo
acidificante (H2SO4) aplicado a dois tipos de efluentes (chorume bruto (WS) e a sua fração
líquida (LF)), sobre as características físico-químicas, as fibras (celulose, hemicelulose e
lenhina) e as emissões gasosas (NH3, CH4, dioxido de carbono (CO2) e N2O) durante o
armazenamento anaeróbio e após aplicação ao solo do efluente animal. A acidificação do
chorume bruto inibiu a degradação de materiais orgânicos (celulose, hemicelulose, matéria
seca, matéria orgânica e do carbono) mas aumentou a concentração de N e reduziu as perdas de
NH3 durante o armazenamento (69%) e depois de aplicação ao solo (93%) relativamente ao
chorume não tratados aditivos biológicos não mostraram qualquer efeito significativo nos
parâmetros analisados. Após aplicação ao solo, as emissões de NH3 a partir do chorume bruto
(18,1 kg N ha−1) foram superiores às observadas a partir da fração líquida (9,3 kg N ha−1) e da
fração sólida compostada (0,3 kg N ha−1).
No Capítulo 3, um sistema especializado para o estudo da desnitrificação em condições
controladas (DENIS), que aplica uma técnica de lavagem da atmosfera do solo, foi usado a uma
temperatura constante de 20 ° C, durante 32 dias, para estudar ou comparar o efeito nos
processos de nitrificação e desnitrificação do tratamento da fração líquida (LF) do chorume por
acidificação (LFA) a pH 5,5, com LF sem tratar e LF tratado com inibidores de nitrificação
(3,4- Dimethylpyrazole phosphate (DMPP)) (LF+DMPP) bem como as emissões gasosas (de
óxido nítrico (NO), N2O e CO2) e dinâmica do azoto mineral do solo. A origem das emissões
de N2O foi estimada como sendo principalmente o processo de desnitrificação. O tratamento
ALF reduziu as emissões de N2O em 52% relativamente ao tratamento LF (não tratado)
enquanto a adição de DMPP reduziu as emissões em cerca de 30%. Relativamente às emissões
de NO, o tratamento ALF atingiu uma redução de 36%, enquanto que a adição de DMPP
permitiu uma redução de 79%.
No Capítulo 4 é descrito um ensaio de campo de 2 anos realizado em Vila Real
(Portugal), entre Julho de 2013 e Maio de 2015. Nesse ensaio, o efeito do tratamento de
chorume por separação mecânica e do tratamento da fração líquida (LF) com aditivos (H2SO4
a um pH 5,5 (LFA) e H2SO4 + DMPP (LFAD)) foi comparado com os tratamentos
convencionais (chorume bruto e fertilizante mineral (nitrato de amónio)) aplicados ao milho
(cultura de verão) e aveia (cultura de inverno), relativamente aos seguintes parâmetros:
produção de matéria seca e qualidade de forragem, exportação de nutrientes, indicadores de
eficiência de utilização do N (Valor de Substituição de Adubos Azotados, calculado com base
na produção de matéria seca (NFRVDM) e recuperação aparente do azoto (ANR)), bem como o
valor residual de N mineral do solo depois de cada cultura. A maior quantidade de matéria seca
(média de 2 anos) foi obtida quando a LFA e a LFAD foram aplicadas. A LFAD aumentou a
concentração de N nas folhas do milho 31,4% relativamente à LF e ao fertilizante mineral. No
caso da aveia, a aplicação de fertilizante mineral conduziu a uma quantidade mais elevada de
matéria seca (4,2 t ha-1), embora não significativamente diferente dos tratamentos WS e LF. O
N exportado no tratamento LF aumentou para valores semelhantes ao fertilizante mineral após
o tratamento com acidificação ou acidificação mais DMPP. Após a colheita do milho, o
potencial de lixiviação de nitratos nos tratamentos com chorume foi inferior ao tratamento com
N mineral.
Conclui-se (Capítulo 5) que a utilização dos aditivos biológicos com o objetivo de
diminuir as emissões gasosas e modificar as características dos chorumes não apresentou
vantagens evidentes. Contudo, a acidificação do chorume é uma tecnologia eficaz na redução
das perdas de NH3, N2O e NO após a aplicação e para aumentar o valor agronómico do efluente
durante o armazenamento. Também, a separação mecânica permite a redução das perdas de
NH3 no campo após a aplicação das frações líquidas, redução que é justificada pela maior
infiltração do efluente no solo, devido ao decréscimo do teor de matéria seca decorrente da
separação mecânica. O ALF pode ser usado como alternativa ao LF+DMPP para mitigar
emissões de N2O, mas no caso das emissões de NO, o ALF não foi tão benéfico como o
LF+DMPP. O chorume tratado por separação mecânica e pelos aditivos não biológicos (H2SO4
ou H2SO4 + DMPP) pode ser uma técnica viável de tratamento de chorume com beneficios
ambientais (potencial de lixiviação inferior) e valor fertilizante equivalente à aplicação de
adubo mineral no sistema de produção milho/aveia nas condições climáticas Mediterrânicas.
An intensive dairy system based on a double crop foraging system has been developed in the North-West of Portugal. This system results in huge volumes of slurry produced annually and although this slurry could be utilized to meet crop nutrient demand, there is limited land for recycling of slurry nutrients. To ensure sustainability of agricultural production in this region, excess slurry needs to be treated or transported to farms in deficit of nutrients. The overall aim of this thesis was to evaluate the environmental and agronomic impacts of the treatment of slurry by mechanical separation and slurry additives under maize/oat double crop foraging system in order to make recommendations for practices that reduces nutrient losses as well as increase crop yield and quality. This thesis is organised into 5 chapters. Chapter 1 provides a-state-of-the-art in relation to nitrogen cycle in dairy systems, gaseous emissions from agriculture, mechanisms and factors controlling ammonia (NH3) volatilization, methane (CH4) and nitrous oxide (N2O) during slurry storage and after application. In this chapter, emphasis is also given to mitigation strategies to minimize emissions of these gases. In chapter 2, the impact of the treatment of slurry using biological additives (EU 200®, Bio-buster® (BB) and JASS®) and an acidifying (H2SO4) additive applied to two effluent types (cattle whole slurry (WS) and its liquid fraction (LF)) on the physical-chemical characteristics, fibre components (cellulose, hemi-cellulose and lignin) and gaseous emissions (NH3, CH4, carbon dioxide (CO2) and N2O) during anaerobic storage and after soil application was evaluated. Slurry acidification inhibited the degradation of organic materials (cellulose, hemicellulose, dry matter, organic matter and total carbon) but increased the N concentrations and reduced NH3 losses during storage (69%) and after soil application (93%) relative to the untreated slurry. Biological additives had no impact on all measured parameters. After soil application, NH3 losses in the WS (18.1 kg N ha−1) was higher than the LF (9.3 kg N ha−1) and composted solid fraction (CSF) (0.3 kg N ha−1). In chapter 3, a specialized denitrification system (DENIS/gas-flow-core technique) was used to study or compare the impact of the treatment of slurry LF by acidification (LFA) to pH 5.5 with the untreated LF and LF treated with a nitrification inhibitor (3,4-Dimethylpyrazole phosphate (DMPP)) (LF+DMPP) on nitrification and denitrification processes as well as gaseous emissions (nitric oxide (NO), N2O and CO2) and nitrogen speciation evolution in the amended soils for 32 days at constant temperature of 20 °C. Emission of N2O was mainly produced from denitrification. The ALF reduced N2O by 52% relative to the untreated LF whereas the DMPP tended to reduce N2O emissions by 30%. The ALF reduced NO emissions by 36% whereas the DMPP led to a greater decrease of 79%. A 2-year field experiment (chapter 4) was conducted in Vila Real, Portugal between July 2013 and May 2015. The impacts of the treatment of slurry by mechanical separation and treatment of the LF with additives (H2SO4 to a pH 5.5 (LFA) and H2SO4+DMPP (LFAD)) were compared with that of the conventional treatments (whole slurry and mineral fertilizer (ammonium nitrate)) applied to maize (summer crop) and oat (autumn/winter crop) relative to the following parameters: forage dry matter yield (DMY) and quality, nutrient removal, N use efficiency indicators (Nitrogen fertilizer replacement value based on dry matter yield (NFRVDM) and apparent nitrogen recovery (ANR)) as well as the residual soil mineral N content after each cropping season. The highest maize DMY (2-year average) of 16.7 t ha−1 was achieved when the LFA and LFAD were applied. The LFAD increased N concentration of maize leaves by 31.4% relative to the LF and Mineral fertilizer. In relation to the oat crop, the mineral fertilizer led to the highest DMY of 4.2 t ha−1 although not significantly different from the WS and LF treatments. The N removal in the LF increased to values comparable to the Mineral fertilizer after treatment with acidification (LFA) or both acidification plus DMPP (LFAD). The nitrate leaching potential in slurry treatments were lower than the mineral fertilizer after maize harvesting. Overall, it was concluded (chapter 5) that the use of the above biological additives to decrease pollutant gases and to modify slurry characteristics are questionable. Slurry acidification is a potent tool to reduce NH3, N2O and NO losses from slurry after application and to increase the agronomic value (mainly N and S concentrations) of slurry during storage. Reducing slurry dry matter through mechanical separation can mitigate NH3 losses from field applied slurry. The NH3 reductions in the LF is mainly related to the higher infiltration of ammonium in the top soil (0-5cm layer) relative to the whole slurry. The ALF can be used as an alternative to LF+DMPP to mitigate N2O emissions but in the case of NO emissions, the ALF was not as beneficial as the LF+DMPP. Slurry treated by mechanical separation plus additives (H2SO4 or H2SO4 + DMPP) can be recommended as a viable technique with environmental benefits (low nitrate leaching potential) and an equivalent fertilizer value as the mineral fertilizer in a maize-oat cropping system under Mediterranean climatic conditions.
An intensive dairy system based on a double crop foraging system has been developed in the North-West of Portugal. This system results in huge volumes of slurry produced annually and although this slurry could be utilized to meet crop nutrient demand, there is limited land for recycling of slurry nutrients. To ensure sustainability of agricultural production in this region, excess slurry needs to be treated or transported to farms in deficit of nutrients. The overall aim of this thesis was to evaluate the environmental and agronomic impacts of the treatment of slurry by mechanical separation and slurry additives under maize/oat double crop foraging system in order to make recommendations for practices that reduces nutrient losses as well as increase crop yield and quality. This thesis is organised into 5 chapters. Chapter 1 provides a-state-of-the-art in relation to nitrogen cycle in dairy systems, gaseous emissions from agriculture, mechanisms and factors controlling ammonia (NH3) volatilization, methane (CH4) and nitrous oxide (N2O) during slurry storage and after application. In this chapter, emphasis is also given to mitigation strategies to minimize emissions of these gases. In chapter 2, the impact of the treatment of slurry using biological additives (EU 200®, Bio-buster® (BB) and JASS®) and an acidifying (H2SO4) additive applied to two effluent types (cattle whole slurry (WS) and its liquid fraction (LF)) on the physical-chemical characteristics, fibre components (cellulose, hemi-cellulose and lignin) and gaseous emissions (NH3, CH4, carbon dioxide (CO2) and N2O) during anaerobic storage and after soil application was evaluated. Slurry acidification inhibited the degradation of organic materials (cellulose, hemicellulose, dry matter, organic matter and total carbon) but increased the N concentrations and reduced NH3 losses during storage (69%) and after soil application (93%) relative to the untreated slurry. Biological additives had no impact on all measured parameters. After soil application, NH3 losses in the WS (18.1 kg N ha−1) was higher than the LF (9.3 kg N ha−1) and composted solid fraction (CSF) (0.3 kg N ha−1). In chapter 3, a specialized denitrification system (DENIS/gas-flow-core technique) was used to study or compare the impact of the treatment of slurry LF by acidification (LFA) to pH 5.5 with the untreated LF and LF treated with a nitrification inhibitor (3,4-Dimethylpyrazole phosphate (DMPP)) (LF+DMPP) on nitrification and denitrification processes as well as gaseous emissions (nitric oxide (NO), N2O and CO2) and nitrogen speciation evolution in the amended soils for 32 days at constant temperature of 20 °C. Emission of N2O was mainly produced from denitrification. The ALF reduced N2O by 52% relative to the untreated LF whereas the DMPP tended to reduce N2O emissions by 30%. The ALF reduced NO emissions by 36% whereas the DMPP led to a greater decrease of 79%. A 2-year field experiment (chapter 4) was conducted in Vila Real, Portugal between July 2013 and May 2015. The impacts of the treatment of slurry by mechanical separation and treatment of the LF with additives (H2SO4 to a pH 5.5 (LFA) and H2SO4+DMPP (LFAD)) were compared with that of the conventional treatments (whole slurry and mineral fertilizer (ammonium nitrate)) applied to maize (summer crop) and oat (autumn/winter crop) relative to the following parameters: forage dry matter yield (DMY) and quality, nutrient removal, N use efficiency indicators (Nitrogen fertilizer replacement value based on dry matter yield (NFRVDM) and apparent nitrogen recovery (ANR)) as well as the residual soil mineral N content after each cropping season. The highest maize DMY (2-year average) of 16.7 t ha−1 was achieved when the LFA and LFAD were applied. The LFAD increased N concentration of maize leaves by 31.4% relative to the LF and Mineral fertilizer. In relation to the oat crop, the mineral fertilizer led to the highest DMY of 4.2 t ha−1 although not significantly different from the WS and LF treatments. The N removal in the LF increased to values comparable to the Mineral fertilizer after treatment with acidification (LFA) or both acidification plus DMPP (LFAD). The nitrate leaching potential in slurry treatments were lower than the mineral fertilizer after maize harvesting. Overall, it was concluded (chapter 5) that the use of the above biological additives to decrease pollutant gases and to modify slurry characteristics are questionable. Slurry acidification is a potent tool to reduce NH3, N2O and NO losses from slurry after application and to increase the agronomic value (mainly N and S concentrations) of slurry during storage. Reducing slurry dry matter through mechanical separation can mitigate NH3 losses from field applied slurry. The NH3 reductions in the LF is mainly related to the higher infiltration of ammonium in the top soil (0-5cm layer) relative to the whole slurry. The ALF can be used as an alternative to LF+DMPP to mitigate N2O emissions but in the case of NO emissions, the ALF was not as beneficial as the LF+DMPP. Slurry treated by mechanical separation plus additives (H2SO4 or H2SO4 + DMPP) can be recommended as a viable technique with environmental benefits (low nitrate leaching potential) and an equivalent fertilizer value as the mineral fertilizer in a maize-oat cropping system under Mediterranean climatic conditions.
Descrição
Tese de Doutoramento em Ciências Agronómicas e Florestais
Palavras-chave
Azoto , Forragem , Produção , Valor nutritivo , Gestão de efluentes animais , Tratamento de chorumes , Emissão de gases