Fósforo e comunidade bacteriana do solo em sucessões de culturas sob semeadura direta
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Data
2019-12-12
Autores
Leite, Hugo Mota Ferreira
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Universidade Estadual Paulista (Unesp)
Resumo
As plantas de cobertura em sucessão nos cultivos agrícolas realizam a ciclagem de P por diversos mecanismos, que podem contribuir para o aumento da eficiência da utilização do P pelas culturas cultivadas subsequentes. Além disso, o cultivo de plantas de cobertura na entressafra modifica a comunidade bacteriana do solo, que tem o potencial de modificar seu ambiente químico. O objetivo do presente trabalho foi avaliar a disponibilidade do fósforo e a comunidade microbiana do solo em diferentes sucessões de culturas conduzidas em SSD por 14 anos. A pesquisa foi realizada nas safras 2016/2017 e 2017/2018, em Nitossolo Vermelho distroférrico, estruturado, de textura argilosa. A área é conduzida na Fazenda Experimental Lageado, UNESP, Botucatu-SP. Os sistemas de sucessão avaliados foram constituídos pelos seguintes cultivos de primavera: milheto (Pennisetum glaucum L.), sorgo forrageiro (Sorghum bicolor (L.) Moench), crotalária (Crotalaria juncea L.), além de uma área de pousio/escarificação. Na camada superficial do solo (0-10 cm), os maiores teores de P inorgânico lábil foram nas sucessões sorgo-soja e pousio/escarificação-soja. Porém, em profundidade, o sorgo obteve maior teor de P inorgânico lábil. A escarificação do solo realizada na área do pousio/escarificação na camada de 0-20 cm aumentou a concentração de P orgânico lábil. Os sistemas de sucessão de culturas com sorgo e crotalária foram eficientes na ciclagem de P. Os atributos químicos do solo, após 14 anos de sucessão de culturas em sistema de semeadura direta, foram modificados pelo cultivo das plantas de cobertura. Em relação aos atributos microbiológicos do solo, as plantas de cobertura proporcionaram aumento nas concentrações de carbono da biomassa microbiana (Cmic) e influenciaram na maior atividade microbiológica do solo. As alterações nos atributos químicos e biológicos do solo pelos sistemas de sucessão de culturas influenciou na composição e abundância das bactérias solubilizadoras de P, principalmente os teores Ca, H+Al e o quociente microbiano (qMIC). Com o cultivo de plantas de cobertura, quanto maior os teores de Pi lábil e Po moderadamente lábil maior a abundância das bactérias solubilizadoras de P.
The cover crops in succession on agricultural rotation perform P cycling by various mechanisms, which may contribute to the increased use efficiency P by subsequent crops. Cultivation of cover crops in inter-harvest changes the soil bacterial community. Like plants, bacteria have the potential to modify their chemical environment by absorbing and releasing ions and organic and inorganic molecules increasing the P availability in soil. The objective of this work was to evaluate the P availability and soil microbial community in different crops succession in no-tillage system conducted for 14 years. The research was carried out during the cycles of 2016/2017 and 2017/2018, in the Typic Rhodudalf. The area is conducted at Experimental Farm Lageado, UNESP, Botucatu-SP. The succession systems evaluated were made up of the following spring crops: pearl millet (Pennisetum glaucum L.), forage sorghum (Sorghum bicolor (L.) Moench), sunn hemp (Crotalaria juncea L.) and besides a fallow/chisel area. In the soil surface layer (0-10 cm), the highest contents of labile inorganic P were in the sorghum-soybean and fallow-soybean successions. However, in depth, sorghum obtained higher labile inorganic P content. For the non-labile inorganic P content in the surface layer, the crop succession systems did not show significant differences. Soil chiseling in the fallow area in the 0-20 cm layer increased the concentration of labile organic P. Sorghum and sunn hemp crop succession systems were efficient in P cycling. The chemical attributes of the soil, after 14 years of succession of crops under no-tillage system, were modified by cultivation of cover crops. Soil microbiological attributes, the cover crops promoted an average increase in soil microbial biomass carbon (Cmic) concentrations and influenced the higher soil microbiological activity. Changes in soil chemical and biological attributes by crop succession systems influenced the composition and abundance of P solubilizing bacteria, especially the Ca, H+Al and microbial quotient (qMIC) contents. With the cultivation of cover crops, the higher concentration of labile inorganic phosphorus and moderately labile organic phosphorus, greater will be abundance of phosphorus solubilizing bacteria.
The cover crops in succession on agricultural rotation perform P cycling by various mechanisms, which may contribute to the increased use efficiency P by subsequent crops. Cultivation of cover crops in inter-harvest changes the soil bacterial community. Like plants, bacteria have the potential to modify their chemical environment by absorbing and releasing ions and organic and inorganic molecules increasing the P availability in soil. The objective of this work was to evaluate the P availability and soil microbial community in different crops succession in no-tillage system conducted for 14 years. The research was carried out during the cycles of 2016/2017 and 2017/2018, in the Typic Rhodudalf. The area is conducted at Experimental Farm Lageado, UNESP, Botucatu-SP. The succession systems evaluated were made up of the following spring crops: pearl millet (Pennisetum glaucum L.), forage sorghum (Sorghum bicolor (L.) Moench), sunn hemp (Crotalaria juncea L.) and besides a fallow/chisel area. In the soil surface layer (0-10 cm), the highest contents of labile inorganic P were in the sorghum-soybean and fallow-soybean successions. However, in depth, sorghum obtained higher labile inorganic P content. For the non-labile inorganic P content in the surface layer, the crop succession systems did not show significant differences. Soil chiseling in the fallow area in the 0-20 cm layer increased the concentration of labile organic P. Sorghum and sunn hemp crop succession systems were efficient in P cycling. The chemical attributes of the soil, after 14 years of succession of crops under no-tillage system, were modified by cultivation of cover crops. Soil microbiological attributes, the cover crops promoted an average increase in soil microbial biomass carbon (Cmic) concentrations and influenced the higher soil microbiological activity. Changes in soil chemical and biological attributes by crop succession systems influenced the composition and abundance of P solubilizing bacteria, especially the Ca, H+Al and microbial quotient (qMIC) contents. With the cultivation of cover crops, the higher concentration of labile inorganic phosphorus and moderately labile organic phosphorus, greater will be abundance of phosphorus solubilizing bacteria.
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Palavras-chave
Fracionamento de P, Plantio direto, 16S rDNA, Microbiologia do solo, Fractionation P, No-till, Soil microbiology, 16S rDNA