Biomassa de forragem e de raizes, gases de efeito estufa e estoque de carbono em pastagem de capim-braquiária em monocultivo ou consorciado com amendoim forrageiro
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2022-07-19
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Universidade Federal de Viçosa
Resumo
A tese foi em elaborada em quatro capítulos, que abordam estudos sobre as características produtivas e químicas da biomassa de forragem e de raízes, do fluxo de gases causadores de efeito estufa e do estoque de carbono nas frações da matéria orgânica do solo em pastos de capim-braquiária em monocultivo ou consorciado com amendoim forrageiro sob diferentes espaçamentos entre linhas de plantio (40, 50, 60, 70 e 80 cm). Capítulo I. Objetivou-se avaliar a biomassa, o acúmulo e a taxa de acúmulo de forragem e a composição química e botânica de pastos de capim-braquiária (Urochloa decumbens cv. Basilisk) em monocultivo (0) e em consórcio com amendoim forrageiro (Arachis pintoi cv. Belmonte), sob diferentes espaçamentos entre linhas de plantio (40, 50, 60, 70 e 80 cm), quatro a cinco anos após a implantação, em delineamento em blocos casualizados, com quatro repetições. Os pastos foram submetidos a lotação intermitente por ovelhas, com altura pré-pastejo de 20 cm e pós-pastejo de 10 cm. Verificou-se que a biomassa seca de gramínea foi influenciada pelos anos, enquanto a biomassa seca de leguminosa e a biomassa seca total de forragem foi afetada pelos sistemas e pelos anos, verificando-se maior biomassa seca de gramínea, de leguminosa e total no segundo ano. Todos os sistemas de consórcio apresentaram maior biomassa seca total em relação ao monocultivo (0). Observou-se efeito de sistemas sobre o percentual de leguminosa, com maior valor no espaçamento de 50 cm (36,3%) em relação ao de 60 cm (23,3%). O acúmulo de forragem foi influenciado pelos sistemas e pelos anos, todavia, a taxa de acúmulo foi afetada apenas pelos sistemas. O acúmulo de forragem nos espaçamentos de 40 e 70 cm foi 65 e 54% mais alto que no monocultivo. No segundo ano de avaliação, detectou-se acúmulo de forragem 30% maior que no primeiro ano. Dentro dos espaçamentos avaliados, as maiores taxas de acúmulo foram encontradas nos espaçamentos de 40 e 70 cm, com valores de 44,7 e 43,9 kg ha-1 dia-1 de MS, respectivamente, em comparação aos 28,1 kg ha-1 dia-1 de MS para o monocultivo. O teor de PB do capim-braquiária foi afetado pela interação sistemas e anos, enquanto os teores de PB do amendoim forrageiro foram afetados pelos anos. O amendoim forrageiro em consorcio com capim-braquiária propicia incrementos satisfatórios na biomassa, na taxa de acúmulo e na composição química da forragem, quatro a cinco anos após seu estabelecimento, independentemente do espaçamento entre linhas. O percentual de leguminosa mantem-se dentro da faixa que propicia benefícios aos sistemas, variando de 23 a 36%, o que implica em pastos consorciados com mais altas concentrações de proteína bruta aos animais em pastejo. Devido aos benefícios quantitativos e qualitativos da inclusão do amendoim forrageiro em pastos de capim-braquiária, recomenda-se sua inclusão em sistemas com lotação intermitente para ovinos. Capítulo II. A decomposição de biomassa de raízes é de extrema importância para a ciclagem e liberação de nutrientes no solo em ecossistemas de pasto, sendo também relacionada ao ciclo de carbono. Objetivou-se avaliar a biomassa e a composição química de raízes de pastos de capim-braquiária (Urochloa decumbens cv. Basilisk) em monocultivo e consorciado com amendoim forrageiro (Arachis pintoi cv. Belmonte), sob diferentes espaçamentos entre linhas de plantio (40, 50, 60, 70 e 80 cm), quatro a cinco anos após a implantação, em delineamento em blocos casualizados, com quatro repetições. Os pastos foram submetidos a lotação intermitente por ovelhas, com altura pré-pastejo de 20 cm e pós- pastejo de 10 cm. A biomassa de raízes foi influenciada pela interação espaçamentos × anos, com menor valor para o monocultivo relativamente aos espaçamentos de 40, 50, 60 e 70 cm, no ano 2. As concentrações de lignina e de C foram influenciadas pelo ano, com valores de 153 e 115 g kg-1 de MO, e, 277 e 139 g C kg-1de MO, com valores 25 e 50% maiores, respectivamente, no ano 1 em relação ao ano 2. A concentração de N foi influenciada pelo espaçamento, com maior concentração no espaçamento 70 cm e menor no monocultivo, e pelo ano, com redução de 45% do ano 1 para o ano 2. A relação lignina/NIDA e C/N foi influenciada pelos efeitos de espaçamentos e de anos, enquanto a relação lignina/N foi influenciada apenas pelos anos. A concentração de NIDA teve efeito da interação espaçamentos × anos, com os espaçamentos de 40 e 50 cm apresentando maiores concentrações no ano 1, enquanto o espaçamento 80 cm apresentou maior concentração no ano 2. Os conteúdos de C e N foram influenciados apenas pelos espaçamentos, com maior conteúdo de C no espaçamento de 50 cm (1.424 kg C ha-1), enquanto o maior conteúdo de N foi observado nos espaçamentos de 40 e 50 cm (122 e 138 kg N ha-1, respectivamente). Recomenda-se que o amendoim forrageiro seja implantado nos espaçamentos entre linhas de 40 e 50 cm, visando o maior sequestro de C e conteúdo de N nas raízes, assim como a melhoria na reciclagem de nutrientes no solo. Capítulo III. Áreas de pasto produtivo, quando comparadas a áreas de pasto degradadas, e até mesmo em comparação a áreas de vegetação nativa, apresentam capacidade superior para estocar carbono no solo. Objetivou-se avaliar os efeitos do monocultivo e consórcio de capim- braquiária (Urochloa decumbens cv. Basilisk) e amendoim forrageiro (Arachis pintoi cv. Belmonte) sobre o estoque de carbono no solo avaliado em quatro sistemas, consistindo de pastos de capim-braquiária em monocultivo e consorciado com amendoim-forrageiro sob diferentes espaçamentos entre linhas de plantio (40, 60 e 80 cm), durante dois anos. O experimento foi conduzido no delineamento em blocos casualizados, com quatro repetições. Os pastos foram submetidos a lotação intermitente por ovelhas, com altura pré-pastejo de 20 cm e pós-pastejo de 10 cm. A quantidade de C na matéria orgânica particulada (MOP), nas profundidades avaliadas de 0-5 e 0-10 cm, foi influenciada pelo fator ano, enquanto na profundidade de 5-10 cm foi afetada pela interação de anos e espaçamentos (p = 0.0333), onde o acréscimo na quantidade de C na MOP variou de 0,2 (80 cm) a 1,84 (monocultivo) Mg C ha- . Entretanto, o C na MOAM não foi afetado por nenhum dos tratamentos. Do ano 1 para o ano 2, o acréscimo no total de C no solo foi de 2,37 Mg ha-1. Embora a inclusão do amendoim forrageiro não tenha demonstrado benefícios no estoque de C no solo, sugere-se que estudos de maior duração sejam efetuados visando melhor entender a relação entre o consórcio do capim- braquiária e o amendoim-forrageiro no sequestro de C no solo. Capítulo IV. A avaliação da emissão de gases causadores do efeito estufa em nível regional é amplamente necessária, pois as métricas utilizadas em relatórios oficiais de emissão são, em grande parte, oriundas de estimativas geradas em regiões extremamente diferentes. Objetivou-se avaliar o fluxo de carbono no solo em pastos de capim-braquiária em monocultivo e consorciado com amendoim forrageiro sobre o fluxo de carbono no solo. O fluxo de C-CO2 e C-CH4 no solo foram avaliados em três sistemas: pasto de capim-braquiária (Urochloa decumbens cv. Basilisk) em monocultivo, pasto de capim-braquiária consorciado com amendoim forrageiro (Arachis pintoi cv. Belmonte), e, área de solo descoberto, sem a presença de biomassa vegetal (controle). O experimento teve duração de dois anos e foi conduzido no delineamento em blocos casualizados, com quatro repetições de área. Os pastos foram submetidos a lotação intermitente por ovelhas, com altura pré-pastejo de 20 cm e pós-pastejo de 10 cm. Verificou-se que o fluxo de C-CO2 foi influenciado pelos sistemas (p>0.0001), pelos anos (p>0.0001) e pelas estações (p>0.0001). A menor emissão foi observada no solo descoberto (controle), não diferindo entre monocultivo e consorcio, enquanto no ano 1 o fluxo de C-CO2 foi 47% superior ao ano 2, como consequência da maior temperatura de solo no ano 1. Entre as estações, a maior emissão de C- CO2 foi observada no período chuvoso. Não foram observados efeitos de nenhum dos fatores estudados sobre o fluxo de C-CH4 do solo. Embora a inclusão do amendoim forrageiro não tenha demonstrado efeitos na emissão de C no solo, sugere-se que estudos mais prolongados sejam efetuados visando melhor entender essa relação. Palavras-chave: Arachis pintoi. Composição botânica. Fluxo. Matéria orgânica. Relação C/N
The PhD Dissertation was developed in four chapters, which cover studies on the productive and chemical characteristics of forage and root biomass, the flow of greenhouse gases and carbon stock in soil organic matter fractions in pastures signal-grass in monoculture or intercropped with forage peanuts under different spacing between planting rows (40, 50, 60, 70 and 80 cm). Chapter I. The objective was to evaluate the biomass, accumulation and accumulation rate of forage and the chemical and botanical composition of signal grass (Urochloa decumbens cv. Basilisk) pastures in monoculture (0) and in intercropping with forage peanuts (Arachis pintoi cv. Belmonte), under different spacing between planting rows (40, 50, 60, 70 and 80 cm), four to five years after implantation, in a randomized block design, with four replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. It was found that the dry biomass of grass was influenced by the years, while the dry biomass of legumes and the total dry biomass of forage were affected by the systems and years, with greater dry biomass of grass, legumes and total in the second year. All intercropping systems showed higher total dry biomass compared to monoculture (0). An effect of systems on the percentage of legumes was observed, with a higher value at 50 cm spacing (36.3%) compared to 60 cm spacing (23.3%). Forage accumulation was influenced by systems and years, however, the accumulation rate was affected only by systems. Forage accumulation in 40 and 70 cm spacings was 65 and 54% higher than in monoculture. In the second year of evaluation, forage accumulation was detected 30% greater than in the first year. Within the spacings evaluated, the highest accumulation rates were found at spacings of 40 and 70 cm, with values of 44.7 and 43.9 kg ha-1 day-1 of DM, respectively, compared to 28.1 kg ha-1 day-1 DM for monoculture. The CP content of signal grass was affected by the interaction of systems and years, while the CP content of forage peanuts was affected by the years. Forage peanuts in intercropping with signal grass provide satisfactory increases in biomass, accumulation rate and chemical composition of the forage, four to five years after its establishment, regardless of row spacing. The percentage of legumes remains within the range that provides benefits to the systems, ranging from 23 to 36%, which implies intercropped pastures with higher concentrations of crude protein for grazing animals. Due to the quantitative and qualitative benefits of including forage peanuts in signal grass pastures, its inclusion in systems with intermittent stocking for sheep is recommended. Chapter II. The decomposition of root biomass is extremely important for the cycling and release of nutrients into the soil in pasture ecosystems, and is also related to the carbon cycle. The objective was to evaluate the biomass and chemical composition of roots of signal grass (Urochloa decumbens cv. Basilisk) in monoculture and intercropped with forage peanut (Arachis pintoi cv. Belmonte), under different spacing between planting rows (40, 50, 60, 70 and 80 cm), four to five years after implantation, in a randomized block design, with four replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. Root biomass was influenced by the spacing × years interaction, with a lower value for the monoculture compared to spacings of 40, 50, 60 and 70 cm, in year 2. Lignin and C concentrations were influenced by the year, with values of 153 and 115 g kg-1 of OM, and 277 and 139 g C kg-1 of OM, with values 25 and 50% higher, respectively, in year 1 in relation to year 2. The N concentration was influenced by spacing, with highest concentration in 70 cm spacing and lowest in monoculture, and by year, with a 45% reduction from year 1 to year 2. The lignin/NIDA and C/N ratio was influenced by the effects of spacing and years, while the Lignin/N ratio was influenced only by years. The NIDA concentration had the effect of the spacing × years interaction, with the 40 and 50 cm spacing showing higher concentrations in year 1, while the 80 cm spacing showed higher concentration in year 2. The C and N contents were influenced only by the spacing, with the highest C content at 50 cm spacing (1,424 kg C ha-1), while the highest N content was observed at 40 and 50 cm spacings (122 and 138 kg N ha-1, respectively). It is recommended that forage peanuts be planted in row spacings of 40 and 50 cm, aiming at greater C sequestration and N content in the roots, as well as improving nutrient recycling in the soil. Chapter III. Areas of productive pasture, when compared to degraded pasture areas, and even compared to areas of native vegetation, have a superior capacity to store carbon in the soil. The objective was to evaluate the effects of monoculture and intercropping of signal grass (Urochloa decumbens cv. Basilisk) and forage peanut (Arachis pintoi cv. Belmonte) on soil carbon stock evaluated in four systems, consisting of signal grass pastures in monoculture and intercropped with forage peanuts under different spacing between planting rows (40, 60 and 80 cm), for two years. The experiment was conducted in a randomized block design, with four replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. The amount of C in particulate organic matter (MOP), at the evaluated depths of 0-5 and 0-10 cm, was influenced by the year factor, while at the depth of 5-10 cm it was affected by the interaction of years and spacing (p = 0.0333), where the increase in the amount of C in MOP varied from 0.2 (80 cm) to 1.84 (monoculture) Mg C ha-1. However, C in MOAM was not affected by any of the treatments. From year 1 to year 2, the increase in total C in the soil was 2.37 Mg ha-1. Although the inclusion of forage peanuts has not demonstrated benefits in the C stock in the soil, it is suggested that longer studies be carried out to better understand the relationship between the consortium of signal grass and forage peanuts in C sequestration in the soil. Chapter IV. The assessment of greenhouse gas emissions at a regional level is largely necessary, as the metrics used in official emission reports largely come from estimates generated in extremely different regions. The objective of this study was to evaluate soil carbon flux in signal grass pastures in monoculture and intercropped with forage peanuts on soil carbon flux. The flux of C-CO2 and C-CH4 in the soil were evaluated in three systems: signal grass (Urochloa decumbens cv. Basilisk) pasture in monoculture, signal grass pasture intercropped with forage peanut (Arachis pintoi cv. Belmonte), and, area of bare soil, without the presence of plant biomass (control). The experiment lasted two years and was conducted in a randomized block design, with four area replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. It was found that the C-CO2 flow was influenced by the systems (p>0.0001), the years (p>0.0001) and the seasons (p>0.0001). The lowest emission was observed in bare soil (control), not differing between monoculture and intercropping, while in year 1 the C-CO2 flux was 47% higher than in year 2, as a consequence of the higher soil temperature in year 1. Among the seasons, the highest C-CO2 emission was observed in the rainy season. No effects of any of the factors studied were observed on soil C-CH4 flux. Although the inclusion of forage peanuts has not demonstrated effects on C emissions in the soil, it is suggested that longer studies be carried out to better understand this relationship. Keywords: Arachis pintoi. Botanical composition. Flow. Organic matter. C/N Ratio
The PhD Dissertation was developed in four chapters, which cover studies on the productive and chemical characteristics of forage and root biomass, the flow of greenhouse gases and carbon stock in soil organic matter fractions in pastures signal-grass in monoculture or intercropped with forage peanuts under different spacing between planting rows (40, 50, 60, 70 and 80 cm). Chapter I. The objective was to evaluate the biomass, accumulation and accumulation rate of forage and the chemical and botanical composition of signal grass (Urochloa decumbens cv. Basilisk) pastures in monoculture (0) and in intercropping with forage peanuts (Arachis pintoi cv. Belmonte), under different spacing between planting rows (40, 50, 60, 70 and 80 cm), four to five years after implantation, in a randomized block design, with four replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. It was found that the dry biomass of grass was influenced by the years, while the dry biomass of legumes and the total dry biomass of forage were affected by the systems and years, with greater dry biomass of grass, legumes and total in the second year. All intercropping systems showed higher total dry biomass compared to monoculture (0). An effect of systems on the percentage of legumes was observed, with a higher value at 50 cm spacing (36.3%) compared to 60 cm spacing (23.3%). Forage accumulation was influenced by systems and years, however, the accumulation rate was affected only by systems. Forage accumulation in 40 and 70 cm spacings was 65 and 54% higher than in monoculture. In the second year of evaluation, forage accumulation was detected 30% greater than in the first year. Within the spacings evaluated, the highest accumulation rates were found at spacings of 40 and 70 cm, with values of 44.7 and 43.9 kg ha-1 day-1 of DM, respectively, compared to 28.1 kg ha-1 day-1 DM for monoculture. The CP content of signal grass was affected by the interaction of systems and years, while the CP content of forage peanuts was affected by the years. Forage peanuts in intercropping with signal grass provide satisfactory increases in biomass, accumulation rate and chemical composition of the forage, four to five years after its establishment, regardless of row spacing. The percentage of legumes remains within the range that provides benefits to the systems, ranging from 23 to 36%, which implies intercropped pastures with higher concentrations of crude protein for grazing animals. Due to the quantitative and qualitative benefits of including forage peanuts in signal grass pastures, its inclusion in systems with intermittent stocking for sheep is recommended. Chapter II. The decomposition of root biomass is extremely important for the cycling and release of nutrients into the soil in pasture ecosystems, and is also related to the carbon cycle. The objective was to evaluate the biomass and chemical composition of roots of signal grass (Urochloa decumbens cv. Basilisk) in monoculture and intercropped with forage peanut (Arachis pintoi cv. Belmonte), under different spacing between planting rows (40, 50, 60, 70 and 80 cm), four to five years after implantation, in a randomized block design, with four replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. Root biomass was influenced by the spacing × years interaction, with a lower value for the monoculture compared to spacings of 40, 50, 60 and 70 cm, in year 2. Lignin and C concentrations were influenced by the year, with values of 153 and 115 g kg-1 of OM, and 277 and 139 g C kg-1 of OM, with values 25 and 50% higher, respectively, in year 1 in relation to year 2. The N concentration was influenced by spacing, with highest concentration in 70 cm spacing and lowest in monoculture, and by year, with a 45% reduction from year 1 to year 2. The lignin/NIDA and C/N ratio was influenced by the effects of spacing and years, while the Lignin/N ratio was influenced only by years. The NIDA concentration had the effect of the spacing × years interaction, with the 40 and 50 cm spacing showing higher concentrations in year 1, while the 80 cm spacing showed higher concentration in year 2. The C and N contents were influenced only by the spacing, with the highest C content at 50 cm spacing (1,424 kg C ha-1), while the highest N content was observed at 40 and 50 cm spacings (122 and 138 kg N ha-1, respectively). It is recommended that forage peanuts be planted in row spacings of 40 and 50 cm, aiming at greater C sequestration and N content in the roots, as well as improving nutrient recycling in the soil. Chapter III. Areas of productive pasture, when compared to degraded pasture areas, and even compared to areas of native vegetation, have a superior capacity to store carbon in the soil. The objective was to evaluate the effects of monoculture and intercropping of signal grass (Urochloa decumbens cv. Basilisk) and forage peanut (Arachis pintoi cv. Belmonte) on soil carbon stock evaluated in four systems, consisting of signal grass pastures in monoculture and intercropped with forage peanuts under different spacing between planting rows (40, 60 and 80 cm), for two years. The experiment was conducted in a randomized block design, with four replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. The amount of C in particulate organic matter (MOP), at the evaluated depths of 0-5 and 0-10 cm, was influenced by the year factor, while at the depth of 5-10 cm it was affected by the interaction of years and spacing (p = 0.0333), where the increase in the amount of C in MOP varied from 0.2 (80 cm) to 1.84 (monoculture) Mg C ha-1. However, C in MOAM was not affected by any of the treatments. From year 1 to year 2, the increase in total C in the soil was 2.37 Mg ha-1. Although the inclusion of forage peanuts has not demonstrated benefits in the C stock in the soil, it is suggested that longer studies be carried out to better understand the relationship between the consortium of signal grass and forage peanuts in C sequestration in the soil. Chapter IV. The assessment of greenhouse gas emissions at a regional level is largely necessary, as the metrics used in official emission reports largely come from estimates generated in extremely different regions. The objective of this study was to evaluate soil carbon flux in signal grass pastures in monoculture and intercropped with forage peanuts on soil carbon flux. The flux of C-CO2 and C-CH4 in the soil were evaluated in three systems: signal grass (Urochloa decumbens cv. Basilisk) pasture in monoculture, signal grass pasture intercropped with forage peanut (Arachis pintoi cv. Belmonte), and, area of bare soil, without the presence of plant biomass (control). The experiment lasted two years and was conducted in a randomized block design, with four area replications. The pastures were subjected to intermittent stocking by sheep, with a pre-grazing height of 20 cm and a post-grazing height of 10 cm. It was found that the C-CO2 flow was influenced by the systems (p>0.0001), the years (p>0.0001) and the seasons (p>0.0001). The lowest emission was observed in bare soil (control), not differing between monoculture and intercropping, while in year 1 the C-CO2 flux was 47% higher than in year 2, as a consequence of the higher soil temperature in year 1. Among the seasons, the highest C-CO2 emission was observed in the rainy season. No effects of any of the factors studied were observed on soil C-CH4 flux. Although the inclusion of forage peanuts has not demonstrated effects on C emissions in the soil, it is suggested that longer studies be carried out to better understand this relationship. Keywords: Arachis pintoi. Botanical composition. Flow. Organic matter. C/N Ratio
Descrição
Palavras-chave
Forragem, Biomassa vegetal, Solos - Teor de compostos orgânicos, Braquiária decumbens, Amendoim, Gases do efeito estufa
Citação
ANJOS, Albert José dos. Biomassa de forragem e de raizes, gases de efeito estufa e estoque de carbono em pastagem de capim-braquiária em monocultivo ou consorciado com amendoim forrageiro. 2022. 105 f. Tese (Doutorado em Zootecnia) - Universidade Federal de Viçosa, Viçosa. 2022.