Dinâmica da matéria orgânica e qualidade do solo em sistemas de produção agropecuários
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2021-06-07
Autores
Soares, Deyvison de Asevedo
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Universidade Estadual Paulista (Unesp)
Resumo
Cada vez mais, a pressão das atividades humanas sobre o meio ambiente, ao longo dos tempos, tem trazido à tona potenciais problemas a serem solucionados em âmbito local, para que seja possível reverter problemas ambientais em escala global. Nesse cenário, os Sistemas Integrados de Produção Agropecuária (SIPAs) reúnem um conjunto de atividades que visam otimizar a produtividade de alimentos ao mesmo tempo em que recupera e melhora a qualidade física, química e biológica do solo e do ambiente, com ganhos econômicos. O objetivo deste estudo foi avaliar os efeitos de sistemas de manejo sobre os atributos físicos, químicos, bioquímicos e a dinâmica da matéria orgânica do solo, pelo fracionamento físico e químico, em solo arenoso do Cerrado. Avaliar, ainda, as produtividades de grãos (PG) do milho, o potencial de forrageiras consorciadas para posterior cobertura do solo, bem como a PG da soja em sucessão. O solo da área experimental foi classificado com Latossolo Vermelho distrófico textura arenosa, localizado no município de Caiuá, São Paulo. Os experimentos foram conduzidos durante as safras 2016/17, 2017/18 e 2018/19. O delineamento experimental foi em blocos casualizados, com sete tratamentos e quatro repetições, sendo os seguintes: S-MRUZ: milho + Urochloa ruziziensis (pastejo) – Soja; S-MPIA: milho + U. brizantha cv. Piatã (pastejo) – Soja; S-MPAI: milho + U. brizantha cv. Paiaguás (pastejo) - Soja; S-MSPD: milho (Plantio direto) – Soja; S-MSPC: milho (preparo convencional) – Soja; S-PIAPERE: soja – capim Piatã (pastejo contínuo); S-PAIPERE: soja – capim Paiaguás (pastejo contínuo). A soja foi cultivada no verão e o consórcio milho + Uroclhoa no outono/inverno. Nas pastagens perenes, novilhos da raça Nelore pastejaram o ano todo, enquanto nos consórcios os animais pastejaram após a colheita do milho. A decomposição da palhada das forrageiras foi avaliada no verão pelo método do litter bags, durante 150 dias, neste período foram determinadas a temperatura e umidade do solo. Foram avaliados a atividade enzimática do solo, atributos químicos, físicos e as frações da matéria orgânica do solo (MOS). No último ano foram avaliados os teores de clorofila nas plantas de soja. Maiores médias de carbono orgânico total e particulado foram obtidos no sistema S-PIAPERE e menores no S-MSPC, em 0 a 0,10 m de profundidade, o que refletiu nos estoques de carbono em superfície e subsuperfície. Em todos os tratamentos o solo apresentou redução percentual da fração humina. Os sistemas conservacionistas apresentaram os maiores teores de ácidos húmicos (C-AH) na camada de 0 a 0,10 m, mas apenas o S-MPAI foi significativamente superior ao S-MSPC. Menores teores de ácidos fúlvicos (C-AF) e C-AH predominaram no S-MSPD e S-MSPC, na camada de 0,20 a 0,40 m. Na avaliação final, os sistemas S-MSPD, S-MPIA e S-MPAI apresentaram os maiores teores de P, o S-MPAI e o S-PIAPERE apresentaram maiores teores de Mg, SB e CTC na camada de 0 a 0,10 m, o S-MPAI apresentou o menor pH e maiores teores de P, Ca, Mg, SB e CTC, o S-PIAPERE apresentou o menor pH e maiores teores de Ca, Mg, SB e V%, na camada de 0,10 a 0,20 m. O maior V% na camada de 0,20 a 0,40 m ocorreu no S-MPAI. Na camada de 0,20 a 0,40 m, ocorreram os maiores teores de B no S-MRUZ e S-MPIA, e maiores teores de Fe no S-MRUZ. No último ano agrícola houve as maiores PG do milho no S-MSPD e maiores PG da soja nos SIPAs (S-MRUZ, S-MPIA e S-MPAI). 23% da palhada foi degradada nos primeiros 30 dias após manejo (DAM), 37% aos 60 DAM e 70% aos 150 DAM. Em geral, os SIPAs apresentaram maior umidade e menor temperatura do solo. Houve predomínio de maior atividade enzimática no solo sob SIPAs, mas apenas a atividade da Arilsulfatase foi significativamente superior no S-MPIA. Os SIPAs proporcionam cobertura para proteção do solo, beneficiando processos envolvidos na ciclagem de nutrientes, comparados ao SPC ou SPD. O consórcio do milho com a BRS Paiaguás foi mais expressivo na melhoria da qualidade do solo e produção das culturas, porém, ressalta-se a superioridade das pastagens perenes. O SPC contínuo deve ser evitado nos solos arenosos. O pastejo animal com taxa de lotação controlada não prejudica a qualidade física do solo. Os SIPAs contribuem para aumentar os teores de C-AH na superfície do solo e tendem a incrementar C-AF, C-AH em profundidade, e estoques de carbono no solo.
Increasingly, the pressure of human activities on the environment, over time, has brought up potential problems that need to be solved at the local level, so that it is possible to reverse environmental problems on a global scale. In this scenario, integrated Crop-Livestock systems (iCL) brings together a set of activities that aim to optimize food productivity while recovering and improving the physical, chemical and biological quality of the soil and the environment, with economic gains. The objective of this study was to evaluate the effects of management systems on the physical, chemical, biochemical attributes and dynamics of soil organic matter, by physical and chemical fractionation, in sandy Cerrado soil. Also evaluate corn grain yields (GY), the potential of intercropped forage for later soil cover, as well as the PG of soybean in succession. The soil in the experimental area was classified as Red Latosol, sandy texture, located in the Caiuá municipality, São Paulo. The experiments were conducted during the 2016/17, 2017/18 and 2018/19 seasons. The experimental design was in randomized blocks, with seven treatments and four repetitions, the treatments were: S-CRUZ: corn + Urochloa ruziziensis grass (grazing) – soybean; S-CPIA: corn + U. brizantha cv. Piatã grass (grazing) – soybean; S-CPAI: corn + U. brizantha cv. Paiaguás grass (grazing) - soybean; S-CNT: corn (no-tillage) – soybean; S-CCT: corn (conventional tillage) – soybean; S-PIAPERE: soybean – Piatã grass (continuous grazing); S-PAIPERE: soybean – Paiaguás grass (continuous grazing). Soybean was grown in the summer and the intercropping corn with Urochloa in the autumn -winter. In perennial pastures, Nellore steers grazed all year round, while in Intercropping the animals graze after the corn harvest. The forage straw decomposition evaluation was carried in the summer out through of litter bags. Soil enzymatic activity, chemical and physical attributes and soil organic matter (SOM) fractions were evaluated. Higher averages of total and particulate organic carbon were obtained in the SPIAPERE system and lower in the S-CCT, at 0 to 0.10 m depth, which reflected in the surface and subsurface carbon stocks. In all treatments, the soil showed a percentage reduction of the humine fraction. Conservation systems showed the highest levels of humic acids (C-HA) in the 0 to 0.10 m layer, but only S-CPAI was significantly higher than S-CCT. Lower levels of fulvic acids (C-FA) and C-HA prevailed in S-CNT and S-CCT, in the 0.20 to 0.40 m layer. In the final evaluation, the S-CNT, S-CPIA and S-CPAI systems and presented the highest levels of P, the S-CPAI and S-PIAPERE had the highest levels of Mg, SB and CEC in the 0 to 0.10 m layer, S-MPAI had the lowest pH and the highest levels of P, Ca, Mg, SB and CEC, S- PIAPERE presented the lowest pH and highest levels of Ca, Mg, SB and V%, in the layer of 0.10 to 0.20 m. The highest V% in the 0.20 to 0.40 m layer occurred in the S-CPAI. In the 0.20 to 0.40 m layer, the highest levels of B occurred in the S-CRUZ and S-CPIA, and the highest levels of Fe in the S-CRUZ. In the last agricultural year, there were the highest GY of corn in S-CSPD and the highest GY of soy in iCLs (S-CRUZ, S-CPIA and S-CPAI). 23% of the straw was degraded in the first 30 days after chemical desiccation (DAD), 37% at 60 DAD and 70% at 150 DAD. In general, the iCLs had higher humidity and lower soil temperature. There was a predominance of higher enzyme activity in the soil under iCLs, but only Arylsulfatase activity was significantly higher in S-CPIA. ICLs provide coverage for soil protection, benefiting processes involved in nutrient cycling, compared to CTS or NTS. corn intercropped with BRS Paiaguás was more expressive in improving soil quality and crop production, however, the superiority of perennial pastures is emphasized. Continuous conventional tillage should be avoided on sandy soils. Animal grazing with controlled stocking rate does not affect the physical quality of the soil. ICLs contribute to increase the levels of C-HA on the soil surface and tend to increase C-FA, C-HA in depth, and carbon stocks in the soil.
Increasingly, the pressure of human activities on the environment, over time, has brought up potential problems that need to be solved at the local level, so that it is possible to reverse environmental problems on a global scale. In this scenario, integrated Crop-Livestock systems (iCL) brings together a set of activities that aim to optimize food productivity while recovering and improving the physical, chemical and biological quality of the soil and the environment, with economic gains. The objective of this study was to evaluate the effects of management systems on the physical, chemical, biochemical attributes and dynamics of soil organic matter, by physical and chemical fractionation, in sandy Cerrado soil. Also evaluate corn grain yields (GY), the potential of intercropped forage for later soil cover, as well as the PG of soybean in succession. The soil in the experimental area was classified as Red Latosol, sandy texture, located in the Caiuá municipality, São Paulo. The experiments were conducted during the 2016/17, 2017/18 and 2018/19 seasons. The experimental design was in randomized blocks, with seven treatments and four repetitions, the treatments were: S-CRUZ: corn + Urochloa ruziziensis grass (grazing) – soybean; S-CPIA: corn + U. brizantha cv. Piatã grass (grazing) – soybean; S-CPAI: corn + U. brizantha cv. Paiaguás grass (grazing) - soybean; S-CNT: corn (no-tillage) – soybean; S-CCT: corn (conventional tillage) – soybean; S-PIAPERE: soybean – Piatã grass (continuous grazing); S-PAIPERE: soybean – Paiaguás grass (continuous grazing). Soybean was grown in the summer and the intercropping corn with Urochloa in the autumn -winter. In perennial pastures, Nellore steers grazed all year round, while in Intercropping the animals graze after the corn harvest. The forage straw decomposition evaluation was carried in the summer out through of litter bags. Soil enzymatic activity, chemical and physical attributes and soil organic matter (SOM) fractions were evaluated. Higher averages of total and particulate organic carbon were obtained in the SPIAPERE system and lower in the S-CCT, at 0 to 0.10 m depth, which reflected in the surface and subsurface carbon stocks. In all treatments, the soil showed a percentage reduction of the humine fraction. Conservation systems showed the highest levels of humic acids (C-HA) in the 0 to 0.10 m layer, but only S-CPAI was significantly higher than S-CCT. Lower levels of fulvic acids (C-FA) and C-HA prevailed in S-CNT and S-CCT, in the 0.20 to 0.40 m layer. In the final evaluation, the S-CNT, S-CPIA and S-CPAI systems and presented the highest levels of P, the S-CPAI and S-PIAPERE had the highest levels of Mg, SB and CEC in the 0 to 0.10 m layer, S-MPAI had the lowest pH and the highest levels of P, Ca, Mg, SB and CEC, S- PIAPERE presented the lowest pH and highest levels of Ca, Mg, SB and V%, in the layer of 0.10 to 0.20 m. The highest V% in the 0.20 to 0.40 m layer occurred in the S-CPAI. In the 0.20 to 0.40 m layer, the highest levels of B occurred in the S-CRUZ and S-CPIA, and the highest levels of Fe in the S-CRUZ. In the last agricultural year, there were the highest GY of corn in S-CSPD and the highest GY of soy in iCLs (S-CRUZ, S-CPIA and S-CPAI). 23% of the straw was degraded in the first 30 days after chemical desiccation (DAD), 37% at 60 DAD and 70% at 150 DAD. In general, the iCLs had higher humidity and lower soil temperature. There was a predominance of higher enzyme activity in the soil under iCLs, but only Arylsulfatase activity was significantly higher in S-CPIA. ICLs provide coverage for soil protection, benefiting processes involved in nutrient cycling, compared to CTS or NTS. corn intercropped with BRS Paiaguás was more expressive in improving soil quality and crop production, however, the superiority of perennial pastures is emphasized. Continuous conventional tillage should be avoided on sandy soils. Animal grazing with controlled stocking rate does not affect the physical quality of the soil. ICLs contribute to increase the levels of C-HA on the soil surface and tend to increase C-FA, C-HA in depth, and carbon stocks in the soil.
Descrição
Palavras-chave
Substâncias húmicas do solo, Carbono orgânico particulado, Fracionamento químico da MOS, Fracionamento físico da MOS, Atividade enzimática do solo, Fertilidade do solo, Produtividade de grãos, Soil humic substances, Particulate organic carbon, Chemical fractionation of SOM, Physical fractionation of SOM, Soil enzyme activity, Soil fertility, Grain yield