Greenhouse gas emissions and N2o mitigation in beef cattle production on tropical pasture
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Data
2016-02-03
Autores
Cardoso, Abmael da Silva [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Metano (CH4) e óxido nitroso (N2O) são dois dos mais importantes gases de efeito estufa emitidos pela pecuária. Eles são produzidos pelas excretas dos animais e fertilizantes. No Brasil, a quantidade emitida destes gases e opções para mitigação foram pouco exploradas. Uma sequência de 4 experimentos foram realizados em campo (em duas estações chuvosas e duas secas, 106 dias de duração cada) com o objetivo de quantificar as emissões de N2O e CH4, volatilização de NH3 e o fator de emissão (FE) quando aplicadas fezes, urina, fezes + urina e fertilizante ureia em Latossolo Vermelho cultivado com capim-marandu. Investigou-se o efeito da umidade do solo e compactação, composição da urina, volume urinário, e adição de fezes sobre as emissões de N2O em um Latossolo recebendo urina manipulada em condições controladas, bem como nas emissões de CH4. Como opção para mitigar as emissões de gases de efeito estufa (GEE) foram estudadas as variáveis como as alturas de pastejo que afetam a magnitude das emissões de GEE; a influência estacional na produção e consumo dos GEE; quais são as variáveis chaves associadas com as emissões de GEE em pastagens de capim-marandu. Adicionalmente, investigou se o efeito dietético dos níveis do sal mineral na concentração de N na urina, o volume urinário, a proporção dos compostos nitrogenados na urina e a concentração de N nas fezes em condições de campo. Os FEs de N2O quantificados diferiram de acordo com a excreta e estação do ano. O FEs foram 2,34%, 4.26% e 3,95% na estação chuvosa e 3.00%, 1.35% e 1.59% na estação seca, respectivamente, para fezes, urina e fezes + urina. O FE do fertilizante ureia foi 0,37%. As emissões médias do CH4 acumuladas foram 99,72, 7,82 e 28,64 (mg C-CH4 m2) para fezes, urina e fezes + urina nesta sequência. Quando manipuladas as condições do solo como umidade, compactação e adição de fezes as emissões de N2O foram influenciadas sendo maiores nos tratamentos com adição de fezes. Ao se variar a concentração do N-urinário aplicado (em igual volume de urina) afetou a produção de N2O diminuindo as emissões da maior para a menor concentração de N aplicada e não foi observado efeito ao se variar o volume de urina aplicado (contendo igual concentração de N-urinário). A concentração de KCl adicionada na urina afetou as emissões de N2O de forma curvilínea enquanto o tipo de composto nitrogenado não. Ao se estudar as emissões de CH4 estas responderam aos fatores do solo como umidade, compactação e adição de fezes e não foram afetadas pela variação da concentração de N-urinário e volumes de urina. A fonte de nitrogênio aplicada não afetou a produção/oxidação de CH4. A altura do pasto, estação e ano afetaram as emissões de N2O e CO2 e a estação as de CH4. As maiores emissões ocorreram no verão e as menores no inverno. A altura do pasto apresentou efeito linear negativo nas emissões de N2O acumuladas anual e linear positivo nas emissões de CO2. O efeito dietético dos níveis de sal mineral influenciaram a concentração de N-urinário, volume de urina, N-ureia, N-alantoína e N-ácido hipurico. A concentração de N-urinário apresentou efeito negativo linear, o volume de urina, N-ureia, N-alantoína e N-ácido hipúrico positivo linear. Enquanto que a excreção total de N excretado via urina, N-creatinina e concentração de N nas fezes não foram afetadas pelos níveis de sal mineral na dieta. As emissões de CH4, N2O e NH3 diferiram dos FEs defaults preconizados pelo IPCC. A umidade e a compactação do solo podem ser os principais fatores que regulam as emissões de N2O e CH4 e depende da variação sazonal da precipitação pluviométrica.
CH4 and N2O are two of the most important greenhouse gas emitted by livestock. They are produced from animal excretes and the fertilizer. In Brazil the amount and options to mitigate these gases are little explored. We carried out a sequence of 4 field-trials (two rainy and two dry season, 106 days each) aimed to quantify the N2O and CH4 emissions, NH3 volatilization and emission factor (EF) after application of dung, urine, dung + urine and urea fertilizer on a Ferralsol of a marandu palisade-grass pastureland of Brazil. We aimed to investigate the effects of soil moisture, soil compaction, urine composition, urine volume, and dung addition on N2O emission from a urine-treated tropical Ferralsol under controlled conditions as well on CH4 emission. As option to mitigate greenhouse gas (GHG) emissions we studied how grazing heights affect the magnitude of GHG emissions; how season influence GHG production and consumption; what are the key driving variables associated with GHG emissions. Additionally, we investigated the effect of dietary mineral salt levels on urine-N concentration, urine volume, the proportion of N compounds in the urine and faeces-N concentration under field conditions. The emissions factor (EF) calculated differed according excretes and season. The EFs were 2.34%, 4.26% and 3.95% in the rainy season and 3.00%, 1.35% and 1.59% in the dry season, respectively, for the dung patches, urine patches and dung + urine. The N2O EF from urea was 0.37%. The averages of CH4 accumulated emissions were 99.72, 7.82 and 28.64 (mg CH4-C m2) for dung, urine and dung + urine in this sequence. The manipulated soil conditions moisture content, compaction, and dung addition affected N2O emissions when varying quantities of urine-N were applied (in equal urine volumes) being higher when added dung and did not affect when varying urine volumes were applied (containing equal quantities of urine-N). The urine-N concentration influenced N2O emissions decreasing from the lower concentration to the higher and the chemical form of urine-N did not. The concentration of KCl added to the urine influenced N2O emissions presenting a curvilinear curve. When the CH4 emissions were influenced by soil factors moisture content, compaction and dung addition and did not responded to the variation in the urine-N concentration and volume. The source of N did not influence the CH4 emissions/oxidation. Pasture height, season and year affect N2O and CO2 emissions and the season CH4 releases. The greater emissions occurred in the summer and the lower in the winter. Pasture height had negative linear effect on annual cumulative N2O emissions and positive linear effect on annual cumulative CO2 emissions. Dietary effects of mineral salt level influenced the N concentration in the urine, urine volume, urea-N, allantoin-N and hyppuric acid. While the total N excreted daily via urine, creatinine-N and N concentration in feces were not affected by mineral salt level in the diet. The emissions of CH4, N2O and NH3 differs that default EFs preconized by the IPCC. Soil moisture and compaction appear to be the main factors regulating N2O and CH4 emissions and depends of the rainfall seasonality.
CH4 and N2O are two of the most important greenhouse gas emitted by livestock. They are produced from animal excretes and the fertilizer. In Brazil the amount and options to mitigate these gases are little explored. We carried out a sequence of 4 field-trials (two rainy and two dry season, 106 days each) aimed to quantify the N2O and CH4 emissions, NH3 volatilization and emission factor (EF) after application of dung, urine, dung + urine and urea fertilizer on a Ferralsol of a marandu palisade-grass pastureland of Brazil. We aimed to investigate the effects of soil moisture, soil compaction, urine composition, urine volume, and dung addition on N2O emission from a urine-treated tropical Ferralsol under controlled conditions as well on CH4 emission. As option to mitigate greenhouse gas (GHG) emissions we studied how grazing heights affect the magnitude of GHG emissions; how season influence GHG production and consumption; what are the key driving variables associated with GHG emissions. Additionally, we investigated the effect of dietary mineral salt levels on urine-N concentration, urine volume, the proportion of N compounds in the urine and faeces-N concentration under field conditions. The emissions factor (EF) calculated differed according excretes and season. The EFs were 2.34%, 4.26% and 3.95% in the rainy season and 3.00%, 1.35% and 1.59% in the dry season, respectively, for the dung patches, urine patches and dung + urine. The N2O EF from urea was 0.37%. The averages of CH4 accumulated emissions were 99.72, 7.82 and 28.64 (mg CH4-C m2) for dung, urine and dung + urine in this sequence. The manipulated soil conditions moisture content, compaction, and dung addition affected N2O emissions when varying quantities of urine-N were applied (in equal urine volumes) being higher when added dung and did not affect when varying urine volumes were applied (containing equal quantities of urine-N). The urine-N concentration influenced N2O emissions decreasing from the lower concentration to the higher and the chemical form of urine-N did not. The concentration of KCl added to the urine influenced N2O emissions presenting a curvilinear curve. When the CH4 emissions were influenced by soil factors moisture content, compaction and dung addition and did not responded to the variation in the urine-N concentration and volume. The source of N did not influence the CH4 emissions/oxidation. Pasture height, season and year affect N2O and CO2 emissions and the season CH4 releases. The greater emissions occurred in the summer and the lower in the winter. Pasture height had negative linear effect on annual cumulative N2O emissions and positive linear effect on annual cumulative CO2 emissions. Dietary effects of mineral salt level influenced the N concentration in the urine, urine volume, urea-N, allantoin-N and hyppuric acid. While the total N excreted daily via urine, creatinine-N and N concentration in feces were not affected by mineral salt level in the diet. The emissions of CH4, N2O and NH3 differs that default EFs preconized by the IPCC. Soil moisture and compaction appear to be the main factors regulating N2O and CH4 emissions and depends of the rainfall seasonality.
Descrição
Palavras-chave
Emissão de CH4 do solo, Mudanças climáticas, Quantificação de N2O, Volatilização de NH3, N2O quantification, NH3 production, CH4 emissions from soil, Climate change