Carbono lábil e nitrogênio mineralizável por incubação anaeróbia em área de produção de milho variando plantas de cobertura e doses de nitrogênio
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Data
2020-12-14
Autores
Costa, Natã Rodrigues
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Universidade Estadual Paulista (Unesp)
Resumo
O manejo do solo com o uso de plantas de cobertura pode favorecer a fertilidade do solo e proporcionar sistemas de produção mais sustentáveis. O objetivo com este trabalho foi avaliar os efeitos do cultivo de plantas de cobertura em pré-safra de milho e de doses de nitrogênio em cobertura na cultura do milho, em experimento de longa duração (dezoito anos): (i) na qualidade do solo por meio da medida do carbono lábil; (ii) no potencial de fornecimento de N do solo para o milho, determinando o carbono orgânico lábil e o N orgânico mineralizável por incubação anaeróbia de curta duração. O delineamento experimental é em blocos casualizados com parcelas subdivididas (“split-plots”), com quatro repetições. Nas parcelas são cultivadas as plantas de cobertura mucuna-cinza (Mucuna cinerea), feijão-de-porco (Canavalia ensiformis) e milheto (Pennisetum americanum), mais um tratamento controle (pousio). Nas subparcelas são aplicadas doses de N (0, 60, 120 e 180 kg ha-1) em cobertura na cultura do milho. Na safra 2018/2019 foram coletadas amostras de solo das profundidades de 0-5, 5-10 e 10-20 cm para avaliar o carbono lábil, oxidável em permanganato de potássio, e o nitrogênio orgânico mineralizável por incubação anaeróbia. Na parte aérea das plantas de milho foi avaliado o acúmulo de N. Na camada de 0-5 cm, o teor de carbono lábil foi menor, 557 mg kg-1 quando a maior dose de N foi aplicada. Em contraposição, o maior valor, 615 mg kg-1, foi obtido quando o N em cobertura deixou de ser aplicado. Ainda nesta camada, o cultivo de plantas de cobertura proporcionou aumentos de 38%, 29% e 19% no N orgânico mineralizável, considerando feijão-de-porco, milheto e mucuna-cinza, respectivamente. Na camada de 5-10 cm, o solo cultivado com mucuna-cinza foi o que apresentou maiores teores de carbono lábil, exceto quando a dose de 120 kg ha-1 de N foi utilizada. Nas camadas de 5-10 e 10-20 cm, a dose de 60 kg ha-1 de N foi a que resultou em maior teor de N orgânico mineralizável. A aplicação de 180 kg ha-1 de N levou aos menores teores de carbono orgânico lábil nas camadas de 5-10 e 10-20 cm de profundidade, quando o milho foi cultivado após o pousio. Contudo, proporcionou maior teor na camada de 10-20 cm quando o milho foi cultivado após as leguminosas mucuna-cinza e feijão-de-porco, demonstrando que o carbono lábil responde de forma diferente à adubação nitrogenada nesta camada, dependendo do tipo de resíduo. O N mineralizado do solo por incubação anaeróbia não se correlacionou com o N acumulado pelas plantas de milho, demonstrando que neste estudo, esta variável não explicou o fornecimento de N do solo para o milho.
Soil management using cover crops can favor soil fertility and provide more sustainable production systems. The objective with this research was to evaluate the effects of the cultivation of cover crops before sowing corn and nitrogen doses in the corn culture, in a long-term experiment (eighteen years): (i) in the soil quality by measuring labile carbon; (ii) in the soil potential for supplying N to corn, determining the labile carbono and the mineralizable organic N by short-term anaerobic incubation. The experimental design is in randomized blocks with split-plots, with four replications. In the plots, the gray velvet bean (Mucuna cinerea), jack bean (Canavalia ensiformis) and pearl millet (Pennisetum americanum) are grown, plus a control treatment (fallow). In the subplots, doses of N (0, 60, 120 and 180 kg ha-1) are applied in sidedress in the corn crop. In the 2018/2019 harvest, soil samples were collected from depths of 0-5, 5-10 and 10-20 cm to evaluate the labile oxidizable carbon in potassium permanganate and mineralizable organic nitrogen by anaerobic incubation. The aerial part of the corn plants was also collected to evaluate the supply of N by the cover plants. In the 0-5 cm layer, the labile carbon content was lower, 557 mg kg-1, when the highest dose of N was applied. In contrast, the highest value, 615 mg kg-1, was obtained when the N in sidedress was not applied. Also in this layer, the cultivation of cover crops provided an increase of 38%, 29% and 19% in the content of mineralizable organic N, considering jack bean, pearl millet and gray velvet bean, respectively. In the 5-10 cm layer, the soil cultivated with gray velvet bean was the one with the highest labile carbon content, except when the dose of 120 kg ha-1 of N was used. In the 5-10 and 10-20 cm layers, the dose of 60 kg ha-1 of N provided the highest content of mineralizable organic N. The application of 180 kg ha-1 of N, provided a lower content of labile organic carbon in the layers of 5-10 and 10-20 cm deep, when the corn was grown after fallow. However, it provided a higher content in 10-20 cm layer when the corn was grown after gray velvet bean and jack bean, demonstrating that labile carbon responds differently to N fertilization in this layer, depending on the type of residue. Mineralizable organic N evaluated by anaerobic incubation did not correlate with the N accumulated by corn plants, demonstrating that in this study, this variable did not explain the N supply from the soil to corn.
Soil management using cover crops can favor soil fertility and provide more sustainable production systems. The objective with this research was to evaluate the effects of the cultivation of cover crops before sowing corn and nitrogen doses in the corn culture, in a long-term experiment (eighteen years): (i) in the soil quality by measuring labile carbon; (ii) in the soil potential for supplying N to corn, determining the labile carbono and the mineralizable organic N by short-term anaerobic incubation. The experimental design is in randomized blocks with split-plots, with four replications. In the plots, the gray velvet bean (Mucuna cinerea), jack bean (Canavalia ensiformis) and pearl millet (Pennisetum americanum) are grown, plus a control treatment (fallow). In the subplots, doses of N (0, 60, 120 and 180 kg ha-1) are applied in sidedress in the corn crop. In the 2018/2019 harvest, soil samples were collected from depths of 0-5, 5-10 and 10-20 cm to evaluate the labile oxidizable carbon in potassium permanganate and mineralizable organic nitrogen by anaerobic incubation. The aerial part of the corn plants was also collected to evaluate the supply of N by the cover plants. In the 0-5 cm layer, the labile carbon content was lower, 557 mg kg-1, when the highest dose of N was applied. In contrast, the highest value, 615 mg kg-1, was obtained when the N in sidedress was not applied. Also in this layer, the cultivation of cover crops provided an increase of 38%, 29% and 19% in the content of mineralizable organic N, considering jack bean, pearl millet and gray velvet bean, respectively. In the 5-10 cm layer, the soil cultivated with gray velvet bean was the one with the highest labile carbon content, except when the dose of 120 kg ha-1 of N was used. In the 5-10 and 10-20 cm layers, the dose of 60 kg ha-1 of N provided the highest content of mineralizable organic N. The application of 180 kg ha-1 of N, provided a lower content of labile organic carbon in the layers of 5-10 and 10-20 cm deep, when the corn was grown after fallow. However, it provided a higher content in 10-20 cm layer when the corn was grown after gray velvet bean and jack bean, demonstrating that labile carbon responds differently to N fertilization in this layer, depending on the type of residue. Mineralizable organic N evaluated by anaerobic incubation did not correlate with the N accumulated by corn plants, demonstrating that in this study, this variable did not explain the N supply from the soil to corn.
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Palavras-chave
Matéria orgânica do solo, Carbono oxidável, Nitrogênio disponível, Gramínea, Leguminosa