Contribuição da cultura de entressafra para a estruturação do solo em área sob sistema de semeadura direta
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Data
2018-12-12
Autores
Fernandes, Mariele Monique Honorato [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Sistemas de cultivo conservacionista, como o sistema de semeadura direta, seguem como princípios, a ausência de preparo do solo, a formação e a manutenção de cobertura vegetal e a rotação de culturas. Contudo, quando uma das premissas não é adequadamente adotada pode haver alterações na estrutura do solo e, consequentemente, nas relações solo-planta. Assim, objetivou-se avaliar os atributos físicos e o carbono orgânico do solo em área com preparo do solo e pousio (vegetação espontânea) na entressafra e em áreas sem preparo do solo, com pousio (vegetação espontânea) e com cultivo na entressafra. As áreas com sistemas de cultivo distintos localizaram-se próximas às coordenadas geodésicas 21°14’05’’S, 48°17’05’’W e altitude média de 550 metros, com clima tipo Aw. O solo das três áreas caracterizou-se como Latossolo Vermelho de textura argilosa (539 g kg-1 de argila na camada de 0,00-0,30 m). Há mais de dez anos, o milho é a principal cultura cultivada no período da safra nas três áreas: sistema de preparo convencional do solo (SPC), com pousio (vegetação espontânea) na entressafra, sistema semeadura direta (SSDE) com pousio (vegetação espontânea) na entressafra e sistema de semeadura direta (SSDM), com cultivo de milho na entressafra. Em cada área coletaram-se 20 amostras de solo em cada uma das camadas, 0,00-0,10 m, 0,10-0,20 m e 0,20-0,30 m de profundidade, em dezembro de 2016, cerca de quinze a vinte dias após a semeadura do milho. Os atributos do solo avaliados foram: diâmetro médio ponderado dos agregados, classes de agregados, índice de estabilidade de agregados, carbono orgânico do solo, teor de argila, teor de areia, macroporosidade, microporosidade, densidade do solo e resistência do solo à penetração. Esses atributos foram submetidos à análise multivariada de fatores, onde se identificou dois processos, o primeiro interpretado como “agregação do solo” e o segundo interpretado como “porosidade do solo”. As respostas dos processos em cada um dos sistemas foram testadas pela análise de variância e as interações significativas entre sistema de cultivo e camada do solo foram analisadas pelo teste de médias de Tukey ao nível de 5% de probabilidade. O processo denominado porosidade do solo sob os sistemas SSDE e SSDM foram semelhantes e ambos menos evidentes do que aquele sob SPC. O processo denominado agregação do solo sob SSDE foi menos evidente que aquele sob SSDM e semelhante àquele sob SPC. Portanto, o cultivo no período da entressafra foi determinante na estruturação do solo em área sob sistema de semeadura direta.
Conservation cropping systems, such as the direct sowing system, follow as principles, the absence of soil preparation, the formation and maintenance of vegetation cover and the crop rotation. However, when one of the assumptions is not properly adopted there may be changes in soil structure and, consequently, in soil-plant relationships.. Thus, the objective was to evaluate the physical attributes and soil organic carbon in na area with soil preparation and fallow in the off season and in areas with no tillage, with fallow and with cultivation in the off season. The areas with distinct cultivation systems were located close to the geodesic coordinates 21°14’05’’S, 48°17’05’’W average altitude of 550 meters with Aw type climate. The soil of the three areas was characterized Red Latosol of clay texture (539 g kg-1 of clay in the layer of 0.00-0.30 m). For more than ten years, maize has been the main cultivated crop during the season in the three areas: conventional tillage system (CTS), fallow in the off season, direct sowing system (DSSS) with fallow (spontaneous vegetation) in the off season, and direct sowing system (DSSC) with corn crop in the off season. In each area 20 soil samples were collected in each of the layers, 0.00 - 0.10 m, 0.10 - 0.20 m and 0.20 - 0.30 m depth, in December 2016, about from fifteen to twenty days after sowing the corn. The soil attributes evaluated were: weighted average diameter of aggregates, aggregate classes, aggregate stability index, soil organic carbon, clay content, sand content, macroporosity, microporosity, soil density and soil resistance to penetration. These atributes were submitted to factor analysis, which two processes were extracted, the first one called "soil aggregation" and the second one called "soil porosity". The processes were tested by analysis of variance and the significant interactions of the cultivation system and soil layer were analyzed by the Tukey's test at the 5% probability level. The process called soil porosity under DSSS and DSSC were similar and both less evident under CTS. The process called soil aggregation under DSSS was less evident than that under DSSC and similar to that under CTS. Therefore, cultivation in the off season was determinant in soil structuring in an area under DSSC.
Conservation cropping systems, such as the direct sowing system, follow as principles, the absence of soil preparation, the formation and maintenance of vegetation cover and the crop rotation. However, when one of the assumptions is not properly adopted there may be changes in soil structure and, consequently, in soil-plant relationships.. Thus, the objective was to evaluate the physical attributes and soil organic carbon in na area with soil preparation and fallow in the off season and in areas with no tillage, with fallow and with cultivation in the off season. The areas with distinct cultivation systems were located close to the geodesic coordinates 21°14’05’’S, 48°17’05’’W average altitude of 550 meters with Aw type climate. The soil of the three areas was characterized Red Latosol of clay texture (539 g kg-1 of clay in the layer of 0.00-0.30 m). For more than ten years, maize has been the main cultivated crop during the season in the three areas: conventional tillage system (CTS), fallow in the off season, direct sowing system (DSSS) with fallow (spontaneous vegetation) in the off season, and direct sowing system (DSSC) with corn crop in the off season. In each area 20 soil samples were collected in each of the layers, 0.00 - 0.10 m, 0.10 - 0.20 m and 0.20 - 0.30 m depth, in December 2016, about from fifteen to twenty days after sowing the corn. The soil attributes evaluated were: weighted average diameter of aggregates, aggregate classes, aggregate stability index, soil organic carbon, clay content, sand content, macroporosity, microporosity, soil density and soil resistance to penetration. These atributes were submitted to factor analysis, which two processes were extracted, the first one called "soil aggregation" and the second one called "soil porosity". The processes were tested by analysis of variance and the significant interactions of the cultivation system and soil layer were analyzed by the Tukey's test at the 5% probability level. The process called soil porosity under DSSS and DSSC were similar and both less evident under CTS. The process called soil aggregation under DSSS was less evident than that under DSSC and similar to that under CTS. Therefore, cultivation in the off season was determinant in soil structuring in an area under DSSC.
Descrição
Palavras-chave
Agregação do solo, Porosidade do solo, Sistema de preparo convencional, Vegetação espontânea, Soil aggregation, Soil porosity, Conventional tillage system, Spontaneous vegetation