Quantidade, qualidade e proteção física do carbono do solo associado à remoção da palha de cana-de-açúcar no sudeste do Brasil
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Data
2022-02-18
Autores
Pimentel, Marcelo Laranjeira
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A remoção da palha da cana-de-açúcar (Saccharum sp.) tem sido considerada uma potencial fonte de energia para aumentar a produção de bioenergia, mas seus impactos na quantidade e qualidade da matéria orgânica do solo (MOS) permanecem pouco lúcidos. No entanto, pouco se sabe sobre como a prática de remoção da palha de cana-de-açúcar afeta a quantidade e estabilização do carbono orgânico do solo (COS) em ambientes tropicais. Foi conduzido um experimento em campo de cana-de-açúcar em blocos casualizados, incluindo tratamentos com diferentes taxas de remoção da palha: remoção total (RT), alta remoção (AR), baixa remoção (BR) e sem remoção (SR), cujas quantidades de 0, 5, 10 e 15 Mg ha-¹ de palha em massa seca foram mantidas sobre a superfície do solo, respectivamente. Os efeitos da remoção de palha em seis anos foram avaliados sobre os estoques de COS do solo e sua dinâmica temporal, bem como nas taxas de COS incorporado no solo via aporte cumulativo de palha. Investigou-se também o efeito da remoção da palha sobre as frações da matéria orgânica particulada (MOP) e associada aos minerais (MOAM) através do fracionamento físico da MOS, e como a palha afeta a distribuição de agregados, o conteúdo de COS dos agregados e a capacidade de preservação do carbono (CPC) nas frações de agregados em diferentes profundidades do solo. Os resultados demonstram que os teores de COS foram maiores sob BR e SR, com exceção da profundidade de 20-30 cm. Os estoques de COS também foram superiores sob BR e SR nas profundidades de 0-10 e 0-30 cm. Os dados indicam que cerca de 24% do C adicionado via palhada foi retido no solo, e a SR apresentou uma taxa de acúmulo de C de 1,42 Mg ha-¹ ano-¹. A baixa remoção de palha aumentou a MOP (46,2%) e MOAM (12,4%) na camada superficial do solo em relação à RT. A manutenção da palha no campo aumentou a proporção de macroagregados do solo, resultando em maiores quantidades de COS preservado nesta fração. SR e BR influenciam positivamente a estocagem de COS, aumentando a fração MOP da MOS e contribuindo para formação de macroagregados do solo, o que é essencial na proteção física do COS à decomposição microbiana. Nas condições deste experimento, a taxa de BR (isto é, 10 Mg ha-1 é mantido no solo, e 5 Mg ha-1 é removido para produção de bioenergia) foi suficiente para aumentar os estoques de COS, enquanto remoções acima desse limite induzem perdas de COS. Os resultados obtidos podem contribuir para a tomada de decisão sobre o manejo da palha para produção sustentável de bioenergia derivada da cana-de-açúcar no Brasil.
Sugarcane (Saccharum spp.) straw removal has been considered a potential source of energy for increasing bioenergy production, but its impacts on quantity and quality of soil organic matter (SOM) remain insufficiently lucid. However, little is known on how the quantity and stabilization of soil organic carbon (SOC) are affected by straw management in tropical environments. A field experiment arranged in randomized blocks was conducted with four replications, which included treatments under different removal rates: total removal (TR), high removal (HR), low removal (LR), and no removal (NR), with quantities of 0, 5, 10 and 15 Mg ha-¹ ha of dry straw maintained on soil surface, respectively. Effects of six-year straw removal to a 30 cm depth were evaluated on SOC stocks and its temporal dynamics, as well as the rates of carbon (C) incorporated into the soil via cumulative straw inputs. Additionally, the effects of straw removal on particulate organic matter (POM) and mineral-associated organic matter (MAOM) fractions were evaluated through physical fractionation of SOM, including how straw removal affects the distribution of aggregates, the C content of aggregates and the carbon preservation capacity (CPC) in fractions of aggregates at different soil depths. Results demonstrate that SOC contents were higher under LR and NR, except at 20-30 cm depth. SOC stocks were also higher under LR and NR at 0-10 cm and 0-30 cm depth. The data indicated that about 24% of the C added via straw were retained in soil, and NR showed a SOC accumulation rate of 1.42 Mg ha-¹ year-¹. Low straw removal increased POM (46.2%) and MAOM (12.4%) in surface layer as compared to TR. Maintenance of straw in the field increased the proportion of soil macroaggregates, resulting in higher amounts of preserved C in this fraction. NR and LR positively influence SOC storage, increasing the POM fraction of SOM, contributing to formation of soil macroaggregates, which is essential for physical protection of SOC against microbial decomposition. Under the conditions of this experiment, the LR rate (i.e., 10 Mg ha-¹ is maintained in the soil, and 5 Mg ha-¹ is removed for bioenergy production) was sufficient for increasing SOC stocks, while removals above this limit tend to induce SOC losses. The results obtained can contribute to decision making on straw management for the sustainable production of bioenergy derived from sugarcane in Brazil.
Sugarcane (Saccharum spp.) straw removal has been considered a potential source of energy for increasing bioenergy production, but its impacts on quantity and quality of soil organic matter (SOM) remain insufficiently lucid. However, little is known on how the quantity and stabilization of soil organic carbon (SOC) are affected by straw management in tropical environments. A field experiment arranged in randomized blocks was conducted with four replications, which included treatments under different removal rates: total removal (TR), high removal (HR), low removal (LR), and no removal (NR), with quantities of 0, 5, 10 and 15 Mg ha-¹ ha of dry straw maintained on soil surface, respectively. Effects of six-year straw removal to a 30 cm depth were evaluated on SOC stocks and its temporal dynamics, as well as the rates of carbon (C) incorporated into the soil via cumulative straw inputs. Additionally, the effects of straw removal on particulate organic matter (POM) and mineral-associated organic matter (MAOM) fractions were evaluated through physical fractionation of SOM, including how straw removal affects the distribution of aggregates, the C content of aggregates and the carbon preservation capacity (CPC) in fractions of aggregates at different soil depths. Results demonstrate that SOC contents were higher under LR and NR, except at 20-30 cm depth. SOC stocks were also higher under LR and NR at 0-10 cm and 0-30 cm depth. The data indicated that about 24% of the C added via straw were retained in soil, and NR showed a SOC accumulation rate of 1.42 Mg ha-¹ year-¹. Low straw removal increased POM (46.2%) and MAOM (12.4%) in surface layer as compared to TR. Maintenance of straw in the field increased the proportion of soil macroaggregates, resulting in higher amounts of preserved C in this fraction. NR and LR positively influence SOC storage, increasing the POM fraction of SOM, contributing to formation of soil macroaggregates, which is essential for physical protection of SOC against microbial decomposition. Under the conditions of this experiment, the LR rate (i.e., 10 Mg ha-¹ is maintained in the soil, and 5 Mg ha-¹ is removed for bioenergy production) was sufficient for increasing SOC stocks, while removals above this limit tend to induce SOC losses. The results obtained can contribute to decision making on straw management for the sustainable production of bioenergy derived from sugarcane in Brazil.
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Palavras-chave
Agregação, Manejo de resíduos de cultura, Matéria orgânica, Agregação dos solos, Carbono