Soil physical properties and soil organic carbon content in northeast Brazil: long-term tillage systems effects

Concerns about the negative effects of agriculture on soil physical quality and soil organic carbon (SOC) pools have spurred on the adoption of conservation tillage systems in tropical regions. This study aimed to evaluate the long-term impacts (16th year) of conventional (CT), minimum (MT) and no-tillage (NT) practices and different cover crops (sunn hemp and a bean/millet sequence) on soil physical properties and SOC content of a corn cultivated Ultisol in the northeast of Brazil. Soil bulk density (Bd), soil penetration resistance (SPR), soil aggregation, and total aggregate-associated carbon (C) (4-2 mm) were evaluated. Tillage practices exerted strong control on soil physical properties and total aggregate-C content but were influenced by cover crop species. Minimum tillage presented the lowest Bd, irrespective of cover crop, while NT with bean/millet sequence resulted in the lowest SPR. However, as regards soil aggregation and total aggregate-C, the results indicated that there were no differences between MT and NT, with both systems presenting greater mean weight diameter (MWD) and total aggregate-C content than CT. Total aggregate-C content in the 0.00-0.05 m soil layer in conservation tillage was increased by the adoption of a bean/millet sequence. Increased mechanical disturbance through CT practices was harmful to Bd, soil aggregation and SOC accrual. Overall, more conservative tillage practices and the proper choice of cover crops might yield greater soil quality. Low intensity of soil disturbances due to the adoption of MT favors soil aggregation and the accrual of SOC in weakly structured soils through increases in contact between organic and mineral particles while not causing significant destruction of soil aggregates.

Soil physical properties and soil organic carbon content in northeast Brazil: long-term tillage systems effects

Concerns about the negative effects of agriculture on soil physical quality and soil organic carbon (SOC) pools have spurred on the adoption of conservation tillage systems in tropical regions. This study aimed to evaluate the long-term impacts (16th year) of conventional (CT), minimum (MT) and no-tillage (NT) practices and different cover crops (sunn hemp and a bean/millet sequence) on soil physical properties and SOC content of a corn cultivated Ultisol in the northeast of Brazil. Soil bulk density (Bd), soil penetration resistance (SPR), soil aggregation, and total aggregate-associated carbon (C) (4-2 mm) were evaluated. Tillage practices exerted strong control on soil physical properties and total aggregate-C content but were influenced by cover crop species. Minimum tillage presented the lowest Bd, irrespective of cover crop, while NT with bean/millet sequence resulted in the lowest SPR. However, as regards soil aggregation and total aggregate-C, the results indicated that there were no differences between MT and NT, with both systems presenting greater mean weight diameter (MWD) and total aggregate-C content than CT. Total aggregate-C content in the 0.00-0.05 m soil layer in conservation tillage was increased by the adoption of a bean/millet sequence. Increased mechanical disturbance through CT practices was harmful to Bd, soil aggregation and SOC accrual. Overall, more conservative tillage practices and the proper choice of cover crops might yield greater soil quality. Low intensity of soil disturbances due to the adoption of MT favors soil aggregation and the accrual of SOC in weakly structured soils through increases in contact between organic and mineral particles while not causing significant destruction of soil aggregates.(AU)

Contribution of tillage systems on the organic matter of Gley soil and the productivity of corn and soybean / Contribuição do sistema de cultivo sobre a matéria orgânica de um Gleissolo e a produtividade do milho e soja

To evaluate the behavior of the organic matter in the profile of Gley soil and the productivity of corn and soybean in a temperate climate (Experimental Station of the University of Purdue - West Lafayette - Indiana - United States - Long: 86º 55' W and Lat: 40º 26' N). The effects of six treatments were studied, derived from three different tillage systems: conventional tillage, minimum tillage, and no tillage, with two successions of crops (soybean-corn and continuous corn), in an experiment conducted in the period of 1980 to 1995, with an experimental design of randomized blocks constituting six treatments arranged in subdivided parcels (split-plot), with three replications. In the experimental plots the treatments of succession of crops and the sub-plot were established with the systems of soil management. The sub-plot was constituted by three tillage systems: conventional tillage, minimum tillage, and no tillage. The soil samples originating from five depths and 11 positions and the data of productivity were analyzed, taken in a transversal line from the plot. With the results it can be concluded that: a) the percentage of organic matter increases in the superficial layer as the movement of the soil diminished, in the following sequence: no tillage system > minimum tillage system > conventional system; b) system of conventional tillage provided greater values of corn yield when associated to continuous crop and in succession with soybean; when compared with conservation tillage; and c) in the conditions of a temperate climate and hydromorphic soil, the content of organic matter showed a relation inversely proportional to productivity, with a smaller performance for the succession of soybean and corn.

O comportamento dos teores de matéria orgânica em um Gleissolo e da produtividade do milho e soja foi avaliado em condição de clima temperado (Estação Experimental da Universidade de Purdue ­ West Lafayette ­ Indiana - Estados Unidos - Long: 86º 55' W e Lat: 40º 26' N). Estudaram-se os efeitos de seis tratamentos (três diferentes sistemas de cultivo: convencional (SC), plantio direto (PD) e cultivo mínimo (CM), com duas sucessões de culturas (soja-milho e milho cultivado continuamente)), com delineamento experimental de blocos casualizados, constituindo seis tratamentos arranjados em parcelas subdivididas (split-plot), com três repetições. Nas parcelas experimentais foram estabelecidos os tratamentos de sucessão das culturas e a sub-parcela, os sistemas de manejo do solo. Analisaram-se amostras de solo provenientes de cinco profundidades em 11 posições, de uma linha transversal na parcela e a produtividade de grãos. Os teores de matéria orgânica aumentam na camada superficial à medida que diminuiu a movimentação do solo, na seguinte seqüência: PD > CM > CC. O CC proporcionou maiores valores de produtividade do milho quando associado ao CM e em sucessão à soja; quando comparado com os sistemas conservacionistas e, nas condições de clima temperado e quando em solos hidromórficos, os teores de matéria orgânica estabelecem relação inversamente proporcional à produtividade, com menor expressão para a sucessão de soja e milho.

Carbon and nitrogen stocks under different management conditions of a yellow-red ultisol, cultivated with sweet corn in Sergipe coastal tablelands / Estoques de carbono e nitrogênio sob diferentes condições de manejo de um Argissolo Vermelho Amarelo, cultivado com milho doce nos tabuleiros costeiros de Sergipe

This study was carried out in a long term experiment and aimed to evaluate the effects of different tillage systems associated with cover crops following sweet corn (Zea mays L.) cultivation on soil C and N stocks. The soil was a red-yellow Ultisol, characteristic of the coastal tableland in the estate of Sergipe. Experimental bands over a split plot scheme were set up with 12 treatments: three management systems (conventional tillage (CC), reduced tillage (CM) and, No-tillage (PD), in the plots, and four cover crops (peanut (Arachis hypogeae), common bean (Phaseolus vulgaris), pigeon pea (Cajanus cajan) and, crotalaria (Crotalaria juncea), in the subplots, with three replications. The highest soil organic carbon input was observed on the No-tillage system as compared to the other tillage systems. As far as N content is concerned, both No-tillage and reduced tillage systems contributed the most. Notillage system associated with cover crops such as Common bean, Peanut and Pigeon pea contributed to a higher soil organic carbon stock while higher N stock was observed when Pigeon pea was associated with reduced tillage system. No-tillage and reduced tillage systems presented higher C and N stocks, respectively, when compared to conventional tillage, improving agriculture sustainability.

O objetivo deste estudo foi analisar o efeito de diferentes sistemas de cultivo com plantas de cobertura em sucessão ao milho doce (Zea mays L.) no estoque de C e N do solo, em experimento de longa duração conduzido em um Argissolo Vermelho-Amarelo nos Tabuleiros Costeiros no Estado de Sergipe. Utilizou-se um sistema de faixas experimentais sob parcelas subdivididas, compostos por 12 tratamentos que associam três manejos de solos (parcelas), compostas por sistema de cultivo convencional (CC), cultivo mínimo (CM) e o sistema plantio direto (PD) e, como subparcelas, quatro plantas, sendo duas comerciais [amendoim (Arachis hypogeae), feijão (Phaseolus vulgaris) e duas de cobertura: [guandu (Cajanus cajan) e crotalária (Crotalaria juncea)], com três repetições. No Plantio Direto houve um maior incremento do carbono orgânico total em comparação aos outros sistemas de manejo.Os sistemas Plantio Direto e Cultivo Mínimo foram os que mais contribuíram para o aumento dos teores de nitrogênio total no solo. As plantas de cobertura feijão, amendoim e guandu proporcionaram maiores estoques de carbono, dentro do sistema Plantio Direto. No Cultivo Mínimo o guandu proporcionou maiores estoques de nitrogênio. Os sistemas Plantio Direto e Cultivo Mínimo apresentaram os maiores estoques de carbono e nitrogênio respectivamente, em comparação ao Cultivo convencional, contribuindo para uma melhor su

Carbon and nitrogen stocks under different management conditions of a yellow-red ultisol, cultivated with sweet corn in Sergipe coastal tablelands / Estoques de carbono e nitrogênio sob diferentes condições de manejo de um Argissolo Vermelho Amarelo, cultivado com milho doce nos tabuleiros costeiros de Sergipe

This study was carried out in a long term experiment and aimed to evaluate the effects of different tillage systems associated with cover crops following sweet corn (Zea mays L.) cultivation on soil C and N stocks. The soil was a red-yellow Ultisol, characteristic of the coastal tableland in the estate of Sergipe. Experimental bands over a split plot scheme were set up with 12 treatments: three management systems (conventional tillage (CC), reduced tillage (CM) and, No-tillage (PD), in the plots, and four cover crops (peanut (Arachis hypogeae), common bean (Phaseolus vulgaris), pigeon pea (Cajanus cajan) and, crotalaria (Crotalaria juncea), in the subplots, with three replications. The highest soil organic carbon input was observed on the No-tillage system as compared to the other tillage systems. As far as N content is concerned, both No-tillage and reduced tillage systems contributed the most. Notillage system associated with cover crops such as Common bean, Peanut and Pigeon pea contributed to a higher soil organic carbon stock while higher N stock was observed when Pigeon pea was associated with reduced tillage system. No-tillage and reduced tillage systems presented higher C and N stocks, respectively, when compared to conventional tillage, improving agriculture sustainability.

O objetivo deste estudo foi analisar o efeito de diferentes sistemas de cultivo com plantas de cobertura em sucessão ao milho doce (Zea mays L.) no estoque de C e N do solo, em experimento de longa duração conduzido em um Argissolo Vermelho-Amarelo nos Tabuleiros Costeiros no Estado de Sergipe. Utilizou-se um sistema de faixas experimentais sob parcelas subdivididas, compostos por 12 tratamentos que associam três manejos de solos (parcelas), compostas por sistema de cultivo convencional (CC), cultivo mínimo (CM) e o sistema plantio direto (PD) e, como subparcelas, quatro plantas, sendo duas comerciais [amendoim (Arachis hypogeae), feijão (Phaseolus vulgaris) e duas de cobertura: [guandu (Cajanus cajan) e crotalária (Crotalaria juncea)], com três repetições. No Plantio Direto houve um maior incremento do carbono orgânico total em comparação aos outros sistemas de manejo.Os sistemas Plantio Direto e Cultivo Mínimo foram os que mais contribuíram para o aumento dos teores de nitrogênio total no solo. As plantas de cobertura feijão, amendoim e guandu proporcionaram maiores estoques de carbono, dentro do sistema Plantio Direto. No Cultivo Mínimo o guandu proporcionou maiores estoques de nitrogênio. Os sistemas Plantio Direto e Cultivo Mínimo apresentaram os maiores estoques de carbono e nitrogênio respectivamente, em comparação ao Cultivo convencional, contribuindo para uma melhor su

Planosol soil sample size for computerized tomography measurement of physical parameters

Computerized tomography (CT) is an important tool in Soil Science for noninvasive measurement of density and water content of soil samples. This work aims to describe the aspects of sample size adequacy for Planosol (Albaqualf) and to evaluate procedures for statistical analysis, using a CT scanner with a 241Am source. Density errors attributed to the equipment are 0.051 and 0.046 Mg m-3 for horizons A and B, respectively. The theoretical value for sample thickness for the Planosol, using this equipment, is 4.0 cm for the horizons A and B. The ideal thickness of samples is approximately 6.0 cm, being smaller for samples of the horizon B in relation to A. Alternatives for the improvement of the efficiency analysis and the reliability of the results obtained by CT are also discussed, and indicate good precision and adaptability of the application of this technology in Planosol (Albaqualf) studies.

A técnica da tomografia computadorizada (TC) permite medir a densidade e a umidade de amostras de solo, constituindo uma importante ferramenta na Ciência do Solo. Este trabalho tem como objetivos descrever os aspectos da adequação do tamanho de amostras de um Planossolo e os procedimentos de avaliação e estudos por análise estatística, empregando-se um minitomógrafo computadorizado de raios gama com fonte de 241Am. O valor do erro atribuído ao equipamento são 0,051 e 0,046 Mg m-3, respectivamente, para os horizontes A e B. O valor teórico da espessura da amostra do Planossolo para uso na técnica de TC com fonte de 241Am é, aproximadamente, 4,0 cm para os horizontes A e B. Já a espessura ideal de amostras é de aproximadamente 6,0 cm, sendo menor para amostras do horizonte B em relação ao A. Obteve-se boa precisão e adaptabilidade no emprego da TC para estudos de Planossolos.

Contribuição do sistema de cultivo sobre a matéria orgânica de um Gleissolo e a produtividade do milho e soja / Contribution of tillage systems on the organic matter of Gley soil and the productivity of corn and soybean soil and the productivity of corn

O comportamento dos teores de matéria orgânica em um Gleissolo e da produtividade do milho e soja foi avaliado em condição de clima temperado (Estação Experimental da Universidade de Purdue West Lafayette Indiana - Estados Unidos - Long: 86º 55 W e Lat: 40º 26 N). Estudaram-se os efeitos de seis tratamentos (três diferentes sistemas de cultivo: convencional (SC), plantio direto (PD) e cultivo mínimo (CM), com duas sucessões de culturas (soja-milho e milho cultivado continuamente)), com delineamento experimental de blocos casualizados, constituindo seis tratamentos arranjados em parcelas subdivididas (split-plot), com três repetições. Nas parcelas experimentais foram estabelecidos os tratamentos de sucessão das culturas e a sub-parcela, os sistemas de manejo do solo. Analisaram-se amostras de solo provenientes de cinco profundidades em 11 posições, de uma linha transversal na parcela e a produtividade de grãos. Os teores de matéria orgânica aumentam na camada superficial à medida que diminuiu a movimentação do solo, na seguinte seqüência: PD > CM > CC. O CC proporcionou maiores valores de produtividade do milho quando associado ao CM e em sucessão à soja; quando comparado com os sistemas conservacionistas e, nas condições de clima temperado e quando em solos hidromórficos, os teores de matéria orgânica estabelecem relação inversamente proporcional à produtividade, co

To evaluate the behavior of the organic matter in the profile of Gley soil and the productivity of corn and soybean in a temperate climate (Experimental Station of the University of Purdue - West Lafayette - Indiana - United States - Long: 86º 55" W and Lat: 40º 26" N). The effects of six treatments were studied, derived from three different tillage systems: conventional tillage, minimum tillage, and no tillage, with two successions of crops (soybean-corn and continuous corn), in an experiment conducted in the period of 1980 to 1995, with an experimental design of randomized blocks constituting six treatments arranged in subdivided parcels (split-plot), with three replications. In the experimental plots the treatments of succession of crops and the sub-plot were established with the systems of soil management. The sub-plot was constituted by three tillage systems: conventional tillage, minimum tillage, and no tillage. The soil samples originating from five depths and 11 positions and the data of productivity were analyzed, taken in a transversal line from the plot. With the results it can be concluded that: a) the percentage of organic matter increases in the superficial layer as the movement of the soil diminished, in the following sequence: no tillage system > minimum tillage system > conventional system; b) system of conventional tillage provided greater values of corn

Planosol soil sample size for computerized tomography measurement of physical parameters

Computerized tomography (CT) is an important tool in Soil Science for noninvasive measurement of density and water content of soil samples. This work aims to describe the aspects of sample size adequacy for Planosol (Albaqualf) and to evaluate procedures for statistical analysis, using a CT scanner with a 241Am source. Density errors attributed to the equipment are 0.051 and 0.046 Mg m-3 for horizons A and B, respectively. The theoretical value for sample thickness for the Planosol, using this equipment, is 4.0 cm for the horizons A and B. The ideal thickness of samples is approximately 6.0 cm, being smaller for samples of the horizon B in relation to A. Alternatives for the improvement of the efficiency analysis and the reliability of the results obtained by CT are also discussed, and indicate good precision and adaptability of the application of this technology in Planosol (Albaqualf) studies.

A técnica da tomografia computadorizada (TC) permite medir a densidade e a umidade de amostras de solo, constituindo uma importante ferramenta na Ciência do Solo. Este trabalho tem como objetivos descrever os aspectos da adequação do tamanho de amostras de um Planossolo e os procedimentos de avaliação e estudos por análise estatística, empregando-se um minitomógrafo computadorizado de raios gama com fonte de 241Am. O valor do erro atribuído ao equipamento são 0,051 e 0,046 Mg m-3, respectivamente, para os horizontes A e B. O valor teórico da espessura da amostra do Planossolo para uso na técnica de TC com fonte de 241Am é, aproximadamente, 4,0 cm para os horizontes A e B. Já a espessura ideal de amostras é de aproximadamente 6,0 cm, sendo menor para amostras do horizonte B em relação ao A. Obteve-se boa precisão e adaptabilidade no emprego da TC para estudos de Planossolos.