Frações de carbono e nitrogênio em solo cultivado com plantas de cobertura em pré-safra de milho
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Data
2022-07-26
Autores
Silva, Amanda Manduca Rosa da [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Na busca pela qualidade de solo é preciso aumentar os teores de carbono e favorecer os processos de transformação das frações da matéria orgânica diretamente associadas ao armazenamento e à disponibilização de nutrientes. O objetivo com este trabalho foi avaliar formas lábeis e estáveis de carbono e de nitrogênio do solo após 20 anos de cultivo de plantas de cobertura em sucessão com milho. O experimento está instalado em Latossolo Vermelho distrófico típico de textura argilosa em delineamento em blocos casualizados com parcelas subdividas e quatro repetições. Os tratamentos são as plantas de cobertura (milheto, mucuna-cinza, crotalária-júncea, feijão-de-porco e vegetação espontânea) cultivadas em pré-safra e adubadas com 120 kg ha-1 N-ureia em cobertura do milho. No ano das avaliações (safra 2020/2021), as plantas de cobertura foram amostradas durante o florescimento para avaliação da produção e caracterização químico-bromatológica e, então, dessecadas. O milho foi semeado em seguida e as amostras de solo foram coletadas aos 7, 52 e 97 dias após a dessecação das plantas de cobertura, nas camadas de 0-5, 5-10 e 10-20 cm de profundidade. Foram avaliados carbono e nitrogênio totais (COT e NT) e as formas de ambos associadas à biomassa microbiana do solo (C-BMS e N-BMS), particuladas (COp e NOp) e associadas aos minerais (COam e NOam). Em relação ao pousio, a sucessão mucuna-cinza/milho favoreceu o acúmulo de C e N nas frações estáveis (COT, NT e NOam) e lábeis (C-BMS, COp e NOp) na camada superficial do solo (0-5 cm), devido às características químicas combinadas de alta concentração de N e de lignina presentes nos resíduos vegetais da mucuna-cinza. Além disso, o cultivo de plantas de cobertura promoveu melhoria da qualidade do solo, demonstrando ser uma estratégia eficiente para sustentabilidade dos sistemas produtivos agrícolas.
In the search for soil quality, it is necessary to increase carbon levels and favor the processes of transformation of organic matter fractions directly associated with the storage and availability of nutrients. The objective with this work was to evaluate labile and stable forms of carbon and nitrogen in the soil after 20 years of cultivation of cover crops in rotation with corn. The experiment is installed in a Rhodic Hapludox, and the cover crops evaluated are millet, velvet bean, sunn hemp, jack bean and spontaneous vegetation (fallow). In the year of evaluations (2020/2021 harvest), cover crops were sampled during flowering to evaluate production and chemical-bromatological characterization and then dried. Corn was then sown and soil samples were collected at 7, 52 and 97 days after desiccation of the cover crops, in layers 0-5, 5-10 and 10-20 cm depth. Total organic carbon and nitrogen (TOC and TN) and the forms of both associated with soil microbial biomass (C-SMB and N-SMB), particulate (POC and PON) and mineral-associated (MAOC and MAON) were evaluated. Regarding fallow, the velvet bean/corn succession proved to be favorable for the accumulation of C and N in the stable (COT, TN and MAON) and labile (C-SMB, POC and PON) fractions in the surface layer of the soil (0-5 cm), due to the combined chemical characteristics of high concentration of N and lignin presente in the vegetal residues of velvet bean. In addition, the cultivation of cover crops improved soil quality, proving to be an efficient strategy for the sustainability of agricultural production systems.
In the search for soil quality, it is necessary to increase carbon levels and favor the processes of transformation of organic matter fractions directly associated with the storage and availability of nutrients. The objective with this work was to evaluate labile and stable forms of carbon and nitrogen in the soil after 20 years of cultivation of cover crops in rotation with corn. The experiment is installed in a Rhodic Hapludox, and the cover crops evaluated are millet, velvet bean, sunn hemp, jack bean and spontaneous vegetation (fallow). In the year of evaluations (2020/2021 harvest), cover crops were sampled during flowering to evaluate production and chemical-bromatological characterization and then dried. Corn was then sown and soil samples were collected at 7, 52 and 97 days after desiccation of the cover crops, in layers 0-5, 5-10 and 10-20 cm depth. Total organic carbon and nitrogen (TOC and TN) and the forms of both associated with soil microbial biomass (C-SMB and N-SMB), particulate (POC and PON) and mineral-associated (MAOC and MAON) were evaluated. Regarding fallow, the velvet bean/corn succession proved to be favorable for the accumulation of C and N in the stable (COT, TN and MAON) and labile (C-SMB, POC and PON) fractions in the surface layer of the soil (0-5 cm), due to the combined chemical characteristics of high concentration of N and lignin presente in the vegetal residues of velvet bean. In addition, the cultivation of cover crops improved soil quality, proving to be an efficient strategy for the sustainability of agricultural production systems.
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Palavras-chave
Biomassa microbiana do solo, Carbono e nitrogênio orgânico particulados, Gramíneas, Plantio direto, Leguminosas forrageira