Emissão de gases do solo, estrutura do dossel e morfogênese do capim marandu submetido a estratégias de intensificação
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Data
2021-05-20
Autores
Ongaratto, Fernando [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A intensificação na produção pecuária é a forma de se obter sustentabilidade e preservar recursos ambientais. Nesse estudo tivemos por objetivo avaliar se o impacto da intensificação do sistema produtivo de bovinos de corte altera as variáveis estruturais, morfogênicas, utilização de nitrogênio e intensidade e intervalo de desfolha do capim Marandu. Objetivou-se também avaliar o fator de emissão de óxido nitroso e metano, fluxos de emissão de óxido nitroso, metano, dióxido de carbono e amônia volatilizada de fezes ou urina, combinadas com dose de nitrato de amônio (N). Foram conduzidos dois experimentos distintos e simultâneos, por dois anos consecutivos, em área de Latossolo Vermelho Amarelo e dossel de Urochloa brizhanta cv. Marandu, em condições de clima tropical. No experimento que avaliou o dossel, foram constituídos três níveis de intensificação de utilização das pastagens (NIUP): Extensivo (zero de nitrogênio), Semi-intensivo (75 kg de N ha-1 ano-1) e intensivo (150 kg de N ha-1 ano-1). Com delineamento em Blocos Casualizados (bloco = ano), sendo três tratamentos, quatro repetições (piquetes), nível de significância de 5 %; sob método de lotação continua e taxa de lotação variável, para manter a altura alvo de 25 cm. A coleta de dados ocorreu no período das águas, de dezembro a abril de 2018/19 e 2019/20. No experimento que avaliou a emissão de gases do efeito estufa, foram constituídos os seguintes tratamentos: Fezes, Fezes + 75 kg de N ha-1 ano-1, Fezes + 150 kg de N ha-1 ano-1, Urina, Urina + 75 kg de N ha-1 ano-1, Urina + 150 kg de N ha-1 ano-1, 75 kg de N ha-1 ano-1 e basal. Com delineamento em Blocos Casualizados (duplo bloqueio = ano e declividade do terreno), sendo oito tratamentos, cinco repetições, nível de significância de 5 %. A coleta de dados ocorreu durante o período das águas e secas, de fevereiro a dezembro de 2019; de janeiro a outubro de 2020. A altura do dossel (25,3 cm) e a massa de forragem (5400 kg MS ha-1) foram similares entre os NIUP. A taxa de lotação, filocrono e o índice de nutrição nitrogenada, foram diferentes entre os três NIUP: Extensivo: 1,8 unidade animal (UA), 13,3 dias e 0,67; Semi-intensivo: 2,8 UA, 11,7 dias e 0,98; Intensivo: 3,8 UA, 9,8 dias e 1,15, respectivamente. A frequência de desfolha (14,9 dias) foi maior no Semi-intensivo e Intensivo. O fator de emissão de óxido nitroso foi maior na Urina (0,60 %), intermediário para Fezes (0,22 %) e menor no 75 kg de nitrato ha-1 ano-1 (0,17 %) e tem efeito linear aditivo para a combinação de fezes ou urina, com nitrato de amônio. O fator de emissão de metano do solo (0,18 kg CH4 animal-1 ano-1) foi similar nos três tratamentos com fezes. E a perda de nitrogênio por amônia volatilizada tem efeito linear decrescente na combinação de fezes ou urina, com nitrato de amônio. Assim a intensificação do sistema produtivo de bovinos de corte é sustentável, pois o dossel propicia aumento de produtividade sem que haja degradação, quando adubado com nitrato de amônio, e os fatores de emissão são menores que os reportados pelo Painel Intergovernamental de Mudanças Climáticas.
The intensification of livestock production is the way to obtain sustainability and preserve environmental resources. In this study we aimed to evaluate whether the impact of the intensification of the beef cattle production system alters the structural, morphogenesis variables, nitrogen utilization and intensity and interval of defoliation of palisadegrass. The aim was also to evaluate the nitrous oxide and methane emission factors, nitrous oxide, methane, carbon dioxide and volatile ammonia emission flows, in dung or urine, combined with ammonium nitrate (N) dose. Two distinct and simultaneous experiments were conducted, for two consecutive years, in an area of typical Hapludox and canopy of Urochloa brizhanta cv. Marandu, in tropical climate conditions. In the experiment which evaluated the canopy, three levels of pasture intensification (LI) were adopted: Extensive (zero nitrogen), Semiintensive (75 kg of N ha-1 year-1 ) and Intensive (150 kg of N ha-1 year-1 ). With a randomized block design (block = year), with three treatments and four repetitions (paddocks), significance level of 5 %; under continuous grazing method and variable stocking rate, to maintain the target height of 25 cm. Data were collected during the wet season, from December to April 2018/19 and 2019/20. In the experiment that evaluated the emission of greenhouse gases, the following treatments were adopted: Feces, Feces + 75 kg of N ha-1 year-1 , Feces + 150 kg of N ha-1 year-1 , Urine, Urine + 75 kg of N ha-1 year-1 , Urine + 150 kg of N ha-1 year-1 , 75 kg of N ha-1 year-1 and Basal. With a randomized block design (block = year and slope of the land), with eight treatments and five repetitions, with significance level of 5 %. Data were collected during the wet and dry season, from February to December 2019 and January to October 2020. The height of the canopy (25.3 cm) and the forage mass (5400 kg DM ha1 ) were similar among LI. The stocking rate, phyllochron and the nitrogen nutrition index differed among the three LI: Extensive: 1.8 animal unit (AU), 13.3 days, 0.67; Semi-intensive: 2.8 AU, 11.7 days, 0.98; Intensive: 3.8 AU, 9.8 days and 1.15, respectively. The interval of defoliation (14.9 days) was higher (P < 0.05) in the Semi-intensive and Intensive system. The nitrous oxide emission factor was higher in Urine (0.60 %), intermediate for Feces (0.22 %) and lower in 75 kg of nitrate ha-1 year-1 (0.17 %) and has a linear additive effect for the combination of feces or urine, with ammonium nitrate. The soil methane emission factor (0.18 kg CH4 animal-1 year-1 ) was similar for the three treatments with feces. And the loss of nitrogen by volatilized ammonia has a decreasing linear effect in the combination of feces or urine, with ammonium nitrate. Thus, the intensification of the beef cattle production system is sustainable, as the canopy provides increased productivity, without degradation, when fertilized with ammonium nitrate, and the emission factors are lower than those reported by the Intergovernmental Panel on Climate Change
The intensification of livestock production is the way to obtain sustainability and preserve environmental resources. In this study we aimed to evaluate whether the impact of the intensification of the beef cattle production system alters the structural, morphogenesis variables, nitrogen utilization and intensity and interval of defoliation of palisadegrass. The aim was also to evaluate the nitrous oxide and methane emission factors, nitrous oxide, methane, carbon dioxide and volatile ammonia emission flows, in dung or urine, combined with ammonium nitrate (N) dose. Two distinct and simultaneous experiments were conducted, for two consecutive years, in an area of typical Hapludox and canopy of Urochloa brizhanta cv. Marandu, in tropical climate conditions. In the experiment which evaluated the canopy, three levels of pasture intensification (LI) were adopted: Extensive (zero nitrogen), Semiintensive (75 kg of N ha-1 year-1 ) and Intensive (150 kg of N ha-1 year-1 ). With a randomized block design (block = year), with three treatments and four repetitions (paddocks), significance level of 5 %; under continuous grazing method and variable stocking rate, to maintain the target height of 25 cm. Data were collected during the wet season, from December to April 2018/19 and 2019/20. In the experiment that evaluated the emission of greenhouse gases, the following treatments were adopted: Feces, Feces + 75 kg of N ha-1 year-1 , Feces + 150 kg of N ha-1 year-1 , Urine, Urine + 75 kg of N ha-1 year-1 , Urine + 150 kg of N ha-1 year-1 , 75 kg of N ha-1 year-1 and Basal. With a randomized block design (block = year and slope of the land), with eight treatments and five repetitions, with significance level of 5 %. Data were collected during the wet and dry season, from February to December 2019 and January to October 2020. The height of the canopy (25.3 cm) and the forage mass (5400 kg DM ha1 ) were similar among LI. The stocking rate, phyllochron and the nitrogen nutrition index differed among the three LI: Extensive: 1.8 animal unit (AU), 13.3 days, 0.67; Semi-intensive: 2.8 AU, 11.7 days, 0.98; Intensive: 3.8 AU, 9.8 days and 1.15, respectively. The interval of defoliation (14.9 days) was higher (P < 0.05) in the Semi-intensive and Intensive system. The nitrous oxide emission factor was higher in Urine (0.60 %), intermediate for Feces (0.22 %) and lower in 75 kg of nitrate ha-1 year-1 (0.17 %) and has a linear additive effect for the combination of feces or urine, with ammonium nitrate. The soil methane emission factor (0.18 kg CH4 animal-1 year-1 ) was similar for the three treatments with feces. And the loss of nitrogen by volatilized ammonia has a decreasing linear effect in the combination of feces or urine, with ammonium nitrate. Thus, the intensification of the beef cattle production system is sustainable, as the canopy provides increased productivity, without degradation, when fertilized with ammonium nitrate, and the emission factors are lower than those reported by the Intergovernmental Panel on Climate Change
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Palavras-chave
Amônia, Bovinos, Metano, Morfogênese, Sustentabilidade, Sustainability