Luis Fernando Stone

Compactação do solo na cultura do feijoeiro. I: efeitos nas propriedades físico-hídricas do solo

O problema de compactacao do solo vem aparecendo sistematicamente na regiao do Cerrado, onde os sistemas convencionais de manejo do solo tem causado desagregacao excessiva da camada aravel, o encrostamento superficial e a formacao de camadas coesas ou compactadas (pe-de-grade ou pe-de-arado). Como alternativa, os agricultores adotaram o Sistema Plantio Direto; entretanto, em varias situacoes vem sendo relatadas ocorrencias de aumento da densidade do solo e diminuicao da macroporosidade, o que tem sido diagnosticado como compactacao, fazendo com que o agricultor seja obrigado a movimentar o solo. Este trabalho teve por objetivo verificar como a compactacao do solo afeta as suas propriedades fisicas e de transmissao de agua. Para isto, utilizaram-se colunas de solo compactadas artificialmente, para produzir densidades do solo de 1,0; 1,2; 1,4 e 1,6 kg dm-3. As propriedades de transmissao de agua foram determinadas com infiltrometros de tensao, para as cargas de pressao de -0,5; -2,0 e -6,0 cm de agua. O aumento da densidade do solo aumentou sua resistencia a penetracao e reduziu linearmente a porosidade total e a macroporosidade. Houve ainda, reducao no tamanho dos poros para o fluxo de agua, reduzindo a condutividade hidraulica do solo. Esta reducao foi mais acentuada na maior carga de pressao testada. Com a carga de pressao de -2,0 cm de agua, a reducao no tamanho dos poros foi parcialmente compensada com aumento do seu numero. O metodo do infiltrometro de tensao mostrou-se adequado em distinguir diferencas nas propriedades de transmissao de agua de um solo submetido a diferentes niveis de compactacao.

Sistemas de preparo do solo e culturas de cobertura na produção orgânica de feijão e milho: I - atributos físicos do solo

Ha necessidade de se avaliar a contribuicao de plantas de cobertura e do seu manejo na manutencao ou melhoria da qualidade fisica do solo em areas sob producao orgânica. Este trabalho objetivou determinar a influencia das plantas de cobertura crotalaria (Crotalaria juncea), guandu (Cajanus cajan (L.) Millsp), mucuna-preta (Mucuna aterrima), sorgo-vassoura (Sorgum technicum) e pousio nos atributos fisicos de solo cultivado com feijao e milho orgânicos, sob semeadura direta (SD) e preparo convencional (PC). O trabalho foi conduzido em Santo Antonio de Goias-GO, em Latossolo Vermelho distrofico, no delineamento de blocos ao acaso, com quatro repeticoes. Em novembro de 2003 foram instalados quatro experimentos, dois em SD e dois em PC, sendo um com feijao e outro com milho em cada sistema. Amostragens do solo das parcelas e de uma mata proxima aos experimentos foram realizadas em novembro de 2007, nas camadas de 0,00-0,10 e 0,10-0,20 m, para determinacao do teor de materia orgânica (MO) e de atributos fisicos do solo. O uso desse solo para a producao agricola, independentemente do sistema de preparo, resultou em reducao no teor de MO e em modificacoes nos seus atributos fisicos, aumentando sua densidade (Ds) e resistencia a penetracao (RP) e reduzindo a macroporosidade (Mp), porosidade total (Pt) e diâmetro medio ponderado dos agregados (DMP). Entretanto, a Ds e a Mp nao atingiram os valores criticos preconizados na literatura como limitantes ao desenvolvimento das culturas. Os sistemas de preparo do solo divergiram quanto ao DMP e a RP. Os atributos fisicos do solo foram alterados favoravelmente pela MO. O indice S correlacionou-se com os atributos fisicos do solo e com o teor de MO, mostrando-se adequado como indicador da qualidade fisica do solo.

Efeitos do sistema de preparo na compactação do solo, disponibilidade hídrica e comportamento do feijoeiro

Neste trabalho foram avaliados os efeitos dos sistemas de preparo com arado de aiveca, com grade aradora e plantio direto, na compactacao do solo, na disponibilidade de agua, no desenvolvimento radicular e na produtividade do feijoeiro (Phaseolus vulgaris L.). A area experimental consistiu de um Latossolo Vermelho-Escuro, sob irrigacao via pivo central, o que possibilitou dois cultivos ao ano. O preparo com arado propiciou menores valores de resistencia a penetracao, ao longo do perfil do solo. O preparo com grade condicionou uma camada mais compacta entre 10 e 24 cm de profundidade e, em plantio direto, houve maior compactacao ate 15 - 22 cm. A distribuicao do sistema radicular, em profundidade, foi mais uniforme no preparo com arado. No preparo com grade houve concentracao das raizes na camada de 0-10 cm de profundidade e, em plantio direto, a concentracao ocorreu ate 20 cm. Sob irrigacao, a menor resistencia do solo a penetracao e a melhor distribuicao do sistema radicular, no preparo com arado, nao possibilitou ao feijoeiro obter maior produtividade em relacao aos outros sistemas de preparo. A maior produtividade observada no plantio direto deveu-se, entre outros fatores, aos menores valores e a menor variacao ao longo do ciclo da tensao matricial da agua no solo, em comparacao aos demais sistemas de preparo do solo.

Produtividade de feijão no sistema plantio direto com aplicação de calcário e zinco

Soil acidity is one of the most limiting factors to yield in crop production in cerrado soils and micronutrientes deficiency is associated to increase in pH of cerrado soil with liming. The objective of this study was to evaluate effects of liming and Zn application to a distrofic Dark-Red Latosol (Typic Haplorthox) on bean yield. A field experiment was conducted during three consecutive years. Lime rates used were 0, 12, and 24 Mg ha-1, and Zn rates were 0, 5, 10, 20, 40, and 80 kg ha-1. Bean yield was significantly increased with the application of lime, however, Zn treatment did not present the same performance. There was a significant change in soil chemical properties at 0-10 and 10-20 cm depths with the application of lime. Values for maximum grain yield were pH 6.6; Ca, 4.0 cmolc kg-1; Mg, 1.2 cmolc kg-1; H+Al, 2.4 cmolc kg-1; acidity saturation, 33.9%; CEC, 7.9 cmolc kg-1; base saturation, 69.3%, Ca saturation, 46.8%; Mg saturation, 15.3%; K saturation, 4.2%; Ca/Mg ratio 4.6; Ca/K ratio 19.1 and Mg/K ratio 6.7 across two soil depths.

Cover crops and physical quality of a Latosol under no-tillage

The objective of this study was to determine the effect of cover crop mulches on the physical quality of a distrophic Red Latosol (Oxisol) under no-tillage. The experiment was carried out under center pivot at Embrapa Rice & Beans, in Santo Antonio de Goias, GO, in a randomized block design, with eight replications. The treatments consisted of eight cover crops: Brachiaria brizantha; corn associated with B. brizantha; pigeon pea; millet; Panicum maximum; sorghum; Stylosanthes guianensis; and Crotalaria juncea. The first seven crops had been cultivated in summer season since December 2001 and C. juncea since November 2003. In the winter season, after cover crop desiccation, irrigated common bean crop under no-tillage was planted. In February 2006, soil organic matter content, some soil physical attributes, and soil physical quality measured by S index were determined. Cover crops, especially grasses, favored soil aggregation at the surface layer. Soil cultivation modified its structure in comparison to native forest, increasing bulk density and reducing macroporosity, total porosity, and soil physical quality. Among the cover crops, pigeon pea, C. juncea, and corn associated with B. brizantha were those that maintained soil surface layer with good physical quality.

Efeitos de sistemas de preparo do solo no uso da água e na produtividade do feijoeiro

Este trabalho teve por objetivo comparar o plantio direto, em duas densidades de palhada, com outros sistemas de preparo do solo, quanto a eficiencia do uso da agua e a produtividade de duas cultivares de feijoeiro com diferentes arquiteturas de planta. O experimento foi conduzido por quatro anos em um Latossolo Vermelho-Escuro, em Santo Antonio de Goias, GO, utilizando o delineamento em faixas, com parcela subdividida, com quatro repeticoes. As faixas A, paralelas a uma linha central de aspersores, consistiram de cinco lâminas de irrigacao. Considerando a media dos quatro anos, as quantidades de agua aplicadas em cada faixa foram de 399,8; 307,0; 216,8; 128,0 e 54,0 mm. As faixas B, transversais a linha central de aspersores, consistiram de cinco sistemas de preparo do solo: plantio direto, plantio direto mais cobertura morta, grade aradora, arado de aiveca e arado escarificador. Nas subparcelas foram plantadas as cultivares de feijao Apore e Safira. A magnitude da resposta da produtividade do feijoeiro a lâmina de agua aplicada variou com a cultivar e com o sistema de preparo do solo. O sistema de plantio direto, com adequada cobertura morta, propiciou maior economia de agua em comparacao aos demais sistemas de preparo do solo.

Compactação do solo na cultura do feijoeiro. II: efeito sobre o desenvolvimento radicular e da parte aérea

This study was conducted with the objective of verifying how soil compaction affects root and shoot development of a bean crop. The experiment was carried out in a greenhouse of Embrapa Rice & Beans, in Santo Antonio de Goias, GO, Brazil, in soil columns packed in PVC tubes 40 cm high and 25 cm of internal diameter. The soil columns were artificially compacted to provide soil bulk densities of 1.0, 1.2, 1.4 and 1.6 kg dm-3 in the 0 - 20 cm soil layer. Bean varieties Perola and BAT 477 were grown in the soil columns. The soil water potential was maintained between -35 and -10 kPa. The evaluations were made at 15, 30, 45, 60, and 72 days after emergence. The root dry matter, root length density, root thickness, leaf area, shoot dry matter, and specific leaf weight were evaluated. The increase in soil compaction negatively affected root and shoot development of bean, the effect being more expressive at bulk density values higher than 1.2 kg dm-3. Perola variety showed more root and shoot development than BAT 477 when there was no physical restriction in the soil for root development. BAT 477, however, was more rustic being less affected by soil compaction and showing higher leaf area and shoot dry matter under this situation.

Micronutrient Deficiency Problems in South America

South America has largest land area at global level to produce food and fibre crops. In addition, climatic conditions (temperature and water availability) are favourable, which further enhances the role of this continent in providing world food security. The Brazilian Cerrado, or savanna, a total area of about 205 Mha of acid soils is a good case in point. Similarly, Colombia, Bolivia, Venezuela, Peru and Ecuador also have large land areas, which can be utilized for crop production. However, the major soils of this continent are acidic and infertile. Hence, liming and fertiliser application are essential. Micronutrient deficiencies are an emerging limiting factor for annual crop production. In annual crops such as rice, corn, wheat, soybean and common bean, deficiencies of Zn, Cu, B, Mn and Fe have been reported. Adopting sound soil and crop management practices will not only enhance crop productivity but also help in reducing deforestation of tropical rainforests in South America. This strategy will permit less CO 2 release to the atmosphere, conservation of soil, water and global climatic change. In South America, micronutrient management issues require a great of deal of research for improvement.

Nitrogênio e água como fatores de produtividade do trigo no cerrado

Two experiments were carried out at Embrapa Rice and Beans, located at the municipality of Santo Antonio de Goias, Goias state, Brazil, under no-tillage in the soybean straw, to evaluate the effects of irrigation management and nitrogen doses on the grain yield and its components of two wheat cultivars. In the first experiment, the irrigation was started at soil-water tension of 40 kPa, and in the second one, at soil-water tension of 60 kPa. For both experiments, a randomized block design with subdivided plots, with four replications, was used. In the plots were established five doses of nitrogen (0, 50, 100, 150, and 200 kg ha-1) and, in the subplots, the cultivars EMBRAPA 22 and EMBRAPA 42. Soil-water tension of 60 kPa was more adequate for management of irrigation in wheat, since it did not affect its grain yield and quality and used less water. The dose of nitrogen that promoted maximum technical efficiency was 73 kg ha-1. The crude protein content increased as nitrogen increased. The increase of irrigation frequency and nitrogen decreased the hectoliter-grain weight.

Soil tillage systems and cover crops in organic production of common bean and corn: II - soil biological properties

The influence of cover crops and their management on the maintenance or improvement of soil physical quality in areas under organic production should be investigated. This study aimed to determine the influence of the cover crops sunn hemp (Crotalaria juncea), pigeon pea (Cajanus cajan (L.) Millsp), velvet bean (Mucuna aterrima), sorghum (Sorgum technicum), and fallow on physical properties of soil under organic cultivation of common bean and corn, in no-tillage (NT) and conventional tillage (CT) systems. The study was conducted in Santo Antonio de Goias-GO, on an Oxisol, in a randomized block design, with four replications. In November 2003 four experiments were installed, two of them under NT and the other two in CT. In each management system, one experiment was carried out with common bean and another with corn. Samples were taken from the layers 0.00-0.10 and 0.10-0.20 m in November 2007, from the plots and from a neighboring native forest, to determine soil organic matter (SOM) and physical properties. The use of this soil for agricultural production, regardless of the tillage system, reduced the SOM content and affected the physical properties, increased bulk density (BD) and soil penetration resistance (PR) and decreased macroporosity (Mp), soil porosity (SP), and the weighted mean diameter of aggregates (WMDA). However, BD and Mp did not reach the critical values indicated in the literature as limiting for crop growth. The soil tillage systems diverged in relation to WMDA and PR. The soil physical properties were favorably affected by SOM. The S index was correlated to the soil physical properties and to SOM and seems to be an adequate indicator of soil physical quality.