Dinâmica do nitrogênio e carbono em um sistema de produção em função da calagem, gessagem e adubação nitrogenada
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Data
2021-06-01
Autores
Barcelos, Jéssica Pigatto de Queiroz [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Altas produtividades das culturas somente são possíveis diante da correção da acidez dos solos e neutralização do alumínio toxico. O calcário aplicado superficialmente tem seu efeito de forma lenta pelo perfil do solo, de forma que a associação com gesso se torna interessante ao aumentar a fertilidade em subsuperfície, favorecendo o crescimento radicular, aumentando o acúmulo de C em profundidade. A dinâmica do nitrogênio (N) e do carbono (C) no sistema solo-planta-atmosfera e a atividade microbiana do solo podem ser influenciadas pela aplicação superficial do calcário e do gesso e pela mudança do pH. Para avaliar a interação entre a aplicação de calcário, gesso e fertilizante nitrogenado nos balanços de N e C, foi realizado um experimento, em sistema de plantio direto com a sucessão de soja – milho safrinha, com milho consorciado com capim Tânzania (Megathyrsus maximus cv Tanzânia) que foi deixado no campo como planta de cobertura. Calcário e gesso foram aplicados antes da semeadura da cultura da soja em outubro de 2016, e novamente em outubro de 2017. Duas doses de N (0 e 160 kg ha-1 de N, sulfato de amônio) foram aplicadas anualmente na cultura do milho. Foram determinadas as entradas e saídas de N e C, e os balanços parciais de N e C. Baseado nos resultados obtidos no experimento de campo, foram realizadas incubações em laboratório com solos de cada tratamento em duas profundidades (0.0-0.10 m e 0.40-0.60 m). Foram adicionados ao solo substratos marcados com 14C em baixas concentrações para determinar a atividade microbiana, a eficiência de uso do C, e a mineralização de C e N do solo. Foi avaliado o perfil da comunidade microbiana do solo de amostras da camada arável, utilizando as metodologias phospholipid fatty acid (PLFA) e sequenciamento Illumina 16S ribosomal RNA (rRNA) amplicon. Embora o balanço parcial de N tenha apresentado resultado negativo, tanto o incremento anual de N no solo foi positivo, assim como o incremento anual de C. Os tratamentos com calcário apresentaram maior potencial de mineralização, e a aplicação de calcário e fertilizante nitrogenado apresentou maior nitrificação no solo. Apesar das diferenças entre a camada arável e o subsolo, e das diferenças nas características do solo causadas pela aplicação de N, a aplicação de calcário e gesso não resulta em diferença na eficiência de uso do 14C-glicose. Entretanto, os resultados não estavam diretamente relacionados ao aumento de pH ocasionado pela aplicação de calcário. Apesar disso, ao aliviar o estresse por acidez do solo, a aplicação de corretivos favoreceu a abundância de grupos microbianos considerados benéficos, como de fungos micorrízicos arbusculares e gêneros de bactérias envolvidas no ciclo do N. Além disso, apesar de não ocorrerem mudanças a nível de Filo, em curto período, as mudanças observadas auxiliam a predizer futuros comportamentos da comunidade microbiana.
High crop yields are only possible when correcting soil acidity and neutralizing toxic aluminium. Lime when applied superficially moves very slowly in the soil profile, hence its association with gypsum is interesting to ameliorate sub-soil fertility favouring root growth, increasing the accumulation of C in depth. The dynamics of nitrogen (N) and carbon (C) in the soil-plant-atmosphere system and the microbial activity of the soil can be influenced by application of lime and gypsum, and consequently change in the soil pH. To evaluate the interaction between the application of lime, gypsum and nitrogen fertilizer in the balances of N and C, an experiment was carried out, in a notillage system with soybean followed by maize-off season, with maize intercropped with guinea grass (Megathyrsus maximus cv Tanzania) as a relay crop. Lime and gypsum were applied before soybean planting in October 2016, and again in October 2017. Two N rates (0, 160 kg ha-1 of N as ammonium sulphate) were applied annually to maize. N and C inputs, outputs and partial N and C balances were determined. Based on the results obtained in the field experiment, incubations were carried out in laboratories with soils from each treatment at two depths (0.0-0.10 m and 0.40-0.60 m). 14C-labelled substrates were added at low concentrations to determinate microbial activity, microbial substrate use efficiency, and C and N mineralization in the soil. We evaluated the soil microbial community profile from topsoil samples, using phospholipid fatty acid (PLFA) and Illumina 16S ribosomal RNA (rRNA) amplicon sequencing. Although the partial balance of N has shown a negative result, both annual increments of C and N in the soil were positive. The treatments with lime showed greater potential for mineralization, and the application of lime and N-fertilizer. presented higher nitrification in the soil. Despite the differences between the topsoil and the subsoil, and the differences in soil characteristics caused by the application of N, the application of lime and gypsum did not result in a difference in the 14C-glucose use efficiency. Thus, the observed results were not directly related to the pH increase caused by the application of limestone. However, soil amendments favour the abundance of beneficial microbial groups such as arbuscular mycorrhizal fungi and bacteria genera involved in N cycle, by alleviating soil acidity stress. Moreover, despite no changes found in the phylum-level in the short term, it assists with the capacity to predict the future behaviours of soil microbial communities.
High crop yields are only possible when correcting soil acidity and neutralizing toxic aluminium. Lime when applied superficially moves very slowly in the soil profile, hence its association with gypsum is interesting to ameliorate sub-soil fertility favouring root growth, increasing the accumulation of C in depth. The dynamics of nitrogen (N) and carbon (C) in the soil-plant-atmosphere system and the microbial activity of the soil can be influenced by application of lime and gypsum, and consequently change in the soil pH. To evaluate the interaction between the application of lime, gypsum and nitrogen fertilizer in the balances of N and C, an experiment was carried out, in a notillage system with soybean followed by maize-off season, with maize intercropped with guinea grass (Megathyrsus maximus cv Tanzania) as a relay crop. Lime and gypsum were applied before soybean planting in October 2016, and again in October 2017. Two N rates (0, 160 kg ha-1 of N as ammonium sulphate) were applied annually to maize. N and C inputs, outputs and partial N and C balances were determined. Based on the results obtained in the field experiment, incubations were carried out in laboratories with soils from each treatment at two depths (0.0-0.10 m and 0.40-0.60 m). 14C-labelled substrates were added at low concentrations to determinate microbial activity, microbial substrate use efficiency, and C and N mineralization in the soil. We evaluated the soil microbial community profile from topsoil samples, using phospholipid fatty acid (PLFA) and Illumina 16S ribosomal RNA (rRNA) amplicon sequencing. Although the partial balance of N has shown a negative result, both annual increments of C and N in the soil were positive. The treatments with lime showed greater potential for mineralization, and the application of lime and N-fertilizer. presented higher nitrification in the soil. Despite the differences between the topsoil and the subsoil, and the differences in soil characteristics caused by the application of N, the application of lime and gypsum did not result in a difference in the 14C-glucose use efficiency. Thus, the observed results were not directly related to the pH increase caused by the application of limestone. However, soil amendments favour the abundance of beneficial microbial groups such as arbuscular mycorrhizal fungi and bacteria genera involved in N cycle, by alleviating soil acidity stress. Moreover, despite no changes found in the phylum-level in the short term, it assists with the capacity to predict the future behaviours of soil microbial communities.
Descrição
Palavras-chave
Solos ácidos, Ciclo do carbono, Ciclo do nitrogênio, Cultivo consorciado, Gases de efeito estufa, Soil, Acid soils, Carbon cycle, Nitrogen cycle, Intercropping, Greenhouse gases