Efeitos do preparo profundo do solo e da calagem sobre a emissão de gases de efeito estufa em cana-de-açúcar
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Data
2021-02-25
Autores
Mendes, Ivanayra da Silva
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Universidade Estadual Paulista (Unesp)
Resumo
As práticas convencionais do sistema de produção da cana-de-açúcar e o uso de processos altamente mecanizados elevam a compactação do solo, acarretando diversos prejuízos no desenvolvimento da cultura e refletindo em baixa produtividade. Também afetam os principais processos biogeoquímicos que regulam o destino do carbono e do nitrogênio, aumentando as emissões de gases de efeito estufa (GEE), que podem estar associados ao aquecimento global. O preparo profundo do solo em faixas com controle de tráfego, principalmente quando acompanhado de doses adequadas de calcário, pode ser uma alternativa na redução dos fluxos dos principais GEE (CO2, CH4 e N2O) emitidos pela agricultura. Contudo, pouco se sabe sobre como essa técnica pode alterar os fluxos destes gases no sistema solo-atmosfera a longo prazo, bem como seus efeitos residuais na compactação do solo. Foram avaliados em solo de textura média, utilizando-se o delineamento experimental em blocos casualizados, com quatro repetições, os seguintes tratamentos: Preparo Convencional (PC) sem e com calcário em área total e Preparo Profundo em faixas (PP) sem e com calcário na linha de plantio no segundo ano da cultura. Os dados foram submetidos à análise de variância (p≤0,05) e comparados pelo teste LSD (p≤0,05). Observou-se maiores fluxos acumulados de CO2 em PP com e de N2O nos manejos sem calcário, enquanto que para o CH4 não se obteve diferenças, o qual atuou como fonte deste gás, porém com valores próximos a zero. O manejo PC com apresentou a maior emissão relativa de C equivalente (ERC) e alta produtividade, enquanto PP com obteve menor ERC, alta produtividade e maior estoque de carbono no solo em relação aos manejos convencionais. As maiores médias de resistência à penetração do solo (RP) nas zonas de cultivos foram observadas nos manejos PP, com valores restritivos para PP sem a partir das camadas 0,1-0,2 m e PP com a 0,3-0,4 m. Em transepto, observou-se que a compactação foi mais atenuada em PC com, onde o mesmo não foi verificado para PP com. O preparo profundo mostrou uma tendência mais rápida e robusta para a compactação ao longo do perfil a partir do segundo ano de cultivo da cana-de-açúcar. A utilização do manejo preparo profundo em faixas aliada a prática da calagem localizada se mostrou promissor para mitigação das emissões relativas de GEE, no armazenamento de C no solo e na produtividade de colmos em área de cana-de-açúcar de primeiro corte. É válido que mais pesquisas precisam ser realizadas para uma avaliação completa nos anos seguintes, principalmente com relação à compactação do solo, por se tratar de uma cultura com ciclo longo, podendo atingir entre 5 a 7 anos, em que diferentes atividades para o manejo da cultura que afetam as propriedades físicas do solo e os fluxos de GEE são realizadas todos os anos.
The conventional practices of the sugarcane production system and the use of highly mechanized processes increase soil compaction, causing several losses in the development of the crop and reflecting on low productivity. They also affect the main biogeochemical processes that regulate the fate of carbon and nitrogen, increasing emissions of greenhouse gases (GHG), which may be associated with global warming. The deep preparation of the soil in bands with traffic control, especially when accompanied by adequate doses of limestone, can be an alternative in reducing the flows of the main GHGs (CO2, CH4 and N2O) emitted by agriculture. However, little is known about how this technique can alter the flow of these gases in the soil-atmosphere system in the long term, as well as their residual effects on soil compaction. The following treatments were evaluated in medium textured soil, using a randomized block design, with four replications, with the following treatments: Conventional Preparation (PC) without and with lime in total area and Deep Preparation in bands (PP) without and with lime in the planting line in the second year of the crop. The data were submitted to analysis of variance (p≤0.05) and compared by the LSD test (p≤0.05). Higher accumulated flows of CO2 in PP with and of N2O were observed in the management without limestone, while for CH4 there were no differences, which acted as a source of this gas, however with values close to zero. The PC com management showed the highest relative C emission (ERC) and high productivity, while PP com had the lowest ERC, high productivity and greater carbon stock in the soil compared to conventional managements. The highest averages of resistance to soil penetration (RP) in the cultivation zones were observed in the PP managements, with restrictive values for PP without from layers 0.1-0.2 m and PP with 0.3-0.4 m. In transept, it was observed that the compaction was more attenuated in PC with, where the same was not verified for PP with. The deep preparation showed a faster and more robust tendency for compaction along the profile from the second year of sugarcane cultivation. The use of deep preparation management in bands combined with the practice of localized liming proved to be promising for mitigating the relative emissions of GHG, in the storage of C in the soil and in the productivity of stalks in the area of first-cut sugarcane. It is valid that more research needs to be carried out for a complete assessment in the following years, mainly in relation to soil compaction, as it is a crop with a long cycle, reaching between 5 and 7 years, in which different activities for the management of crops that affect the physical properties of the soil and the GHG flows are carried out every year.
The conventional practices of the sugarcane production system and the use of highly mechanized processes increase soil compaction, causing several losses in the development of the crop and reflecting on low productivity. They also affect the main biogeochemical processes that regulate the fate of carbon and nitrogen, increasing emissions of greenhouse gases (GHG), which may be associated with global warming. The deep preparation of the soil in bands with traffic control, especially when accompanied by adequate doses of limestone, can be an alternative in reducing the flows of the main GHGs (CO2, CH4 and N2O) emitted by agriculture. However, little is known about how this technique can alter the flow of these gases in the soil-atmosphere system in the long term, as well as their residual effects on soil compaction. The following treatments were evaluated in medium textured soil, using a randomized block design, with four replications, with the following treatments: Conventional Preparation (PC) without and with lime in total area and Deep Preparation in bands (PP) without and with lime in the planting line in the second year of the crop. The data were submitted to analysis of variance (p≤0.05) and compared by the LSD test (p≤0.05). Higher accumulated flows of CO2 in PP with and of N2O were observed in the management without limestone, while for CH4 there were no differences, which acted as a source of this gas, however with values close to zero. The PC com management showed the highest relative C emission (ERC) and high productivity, while PP com had the lowest ERC, high productivity and greater carbon stock in the soil compared to conventional managements. The highest averages of resistance to soil penetration (RP) in the cultivation zones were observed in the PP managements, with restrictive values for PP without from layers 0.1-0.2 m and PP with 0.3-0.4 m. In transept, it was observed that the compaction was more attenuated in PC with, where the same was not verified for PP with. The deep preparation showed a faster and more robust tendency for compaction along the profile from the second year of sugarcane cultivation. The use of deep preparation management in bands combined with the practice of localized liming proved to be promising for mitigating the relative emissions of GHG, in the storage of C in the soil and in the productivity of stalks in the area of first-cut sugarcane. It is valid that more research needs to be carried out for a complete assessment in the following years, mainly in relation to soil compaction, as it is a crop with a long cycle, reaching between 5 and 7 years, in which different activities for the management of crops that affect the physical properties of the soil and the GHG flows are carried out every year.
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Palavras-chave
Sacharum spp., Dióxido de carbono, Metano, Óxido Nitroso, Calcário, Carbon dioxide, Methane, Nitrous oxide, Limestone