ABSTRACT Oxisols ( Latossolos ) are widely distributed in tropical zones and generally characterized by high levels of surface and subsurface acidity. In Brazil, most Oxisols are managed under no-till conditions with surface application of acidity amendments. This study aimed to evaluate lime application strategies (incorporated and surface) for achieving the desired soil base saturation (BS%) levels (44, 60, 70, and 90 %) and the effect of phosphogypsum + lime application on soil chemical properties as well as wheat and corn yield in southern Brazil. Lime incorporation was more effective in reducing the soil acidity and increasing Ca2+ and Mg2+ despite a decrease in organic matter at the soil surface. Phosphogypsum application increased S-SO42- and Ca2+ availability throughout the deeper soil layers and reduced the Mg2+ content in the surface layer. Wheat yield under incorporated lime conditions increased with BS% up to 75, but there was no response to surface application. When phosphogypsum was applied, the wheat yield increased by 8.4 %. For corn, incorporated lime increased the yield up to 445 kg ha-1, which was equivalent to the yield after phosphogypsum application. An increase in the S-SO42- level was the main factor related to the increase in crop yields. In the short term, our results suggest that phosphogypsum applied along with lime is more appropriate than incorporating lime under no-till management conditions.

RESUMO: O objetivo deste trabalho foi avaliar o controle de cominho (Fimbristylis miliacea ) e a seletividade à cultura do arroz irrigado com a mistura em tanque de bispyribac-sodium + metsulfuron-methyl associada a adjuvantes. Conduziu-se o experimento no município de Douradina (23º12'32,0" Sul, 53º17'39,9" Oeste), PR, no ano agrícola 2012/2013. O delineamento experimental utilizado foi o de blocos completos casualizados com dez tratamentos e quatro repetições. Os tratamentos foram constituídos pela aplicação da mistura em tanque dos herbicidas bispyribac-sodium + metsulfuron-methyl, em duas doses (32+1,3 e 40+3,3 g i.a. ha-1), e com adjuvantes Iharaguen(r) (375 mL.ha-1), Orobor N1(r) (75 mL.ha-1), LI 700(r) (150 mL.ha-1) e TA 35(r) (50 mL.ha-1), assim como de testemunha capinada e sem capina. Apesar de a eficácia de controle de cominho (F. miliacea ) com a mistura em tanque de bispyribac-sodium + metsulfuron-methyl associada aos adjuvantes Iharaguen(r) e Orobor N1(r) ter sido significativamente superior ao LI 700(r) e TA 35(r), não foram constatadas diferenças significativas entre os tratamentos em termos de seletividade e produtividade de grãos para o cultivar de arroz Epagri 108.

ABSTRACT: This study aimed to evaluate the control of globe fringerush (Fimbristylis miliacea ) and selectivity to rice crop irrigated with an in-tank mixture of bispyribac-sodium + metsulfuron-methyl associated with adjuvants. The experiment was conducted in the municipality of Douradina, Paraná state, Brazil (23º12'32.0" South, 53º17'39.9" West), in the agricultural year of 2012/2013. An experimental randomized complete block design with ten treatments and four replications was used. The treatments consisted of applying an in-tank mixture of the herbicides bispyribac-sodium + metsulfuron-methyl at two doses (32+1.3 and 40+3.3 g ai ha-1) associated with the adjuvants Iharaguen(tm) (375 mL.ha-1), Orobor N1(tm) (75 mL.ha-1), LI 700(tm) (150 mL.ha-1) and TA 35(tm) (50 mL.ha-1), as well as weeded and unweeded control. Although the effectiveness of globe fringerush (F. miliacea ) control with the in-tank mixture of the herbicides bispyribac-sodium + metsulfuron-methyl associated with Iharaguen(tm) and Orobor N1(tm) has been significantly higher than the effectiveness of these herbicides associated with LI 700(tm) and TA 35(tm), there were no significant differences among the treatments in terms of selectivity and grains yield of the rice cultivar Epagri 108.

A compreensão e a quantificação do impacto dos sistemas de uso e manejo nos teores de C orgânico do solo (COS) e em propriedades físicas são fundamentais para o desenvolvimento de sistemas agrícolas sustentáveis. O objetivo deste trabalho foi avaliar alterações em alguns atributos físicos e COS de um Latossolo Vermelho da região noroeste do Paraná sob diferentes sistemas de uso e manejo: mata nativa, pastagem e as culturas de mandioca e de cana-de-açúcar. Foram coletadas amostras deformadas para determinação da textura, da densidade de partículas, do ensaio de Proctor normal e dos teores de matéria orgânica; e amostras indeformadas, para determinação da densidade do solo (Ds) e porosidade do solo. Os resultados indicaram que os sistemas de manejo estudados induziram alterações nos atributos físicos do solo em relação à mata nativa, o que foi verificado pelos maiores valores de Ds, densidade relativa do solo e densidade máxima do solo e menores valores de macroposidade, porosidade total, COS e estoque de C do solo, na seguinte ordem crescente: pastagem, mandioca e cana-de-açúcar. Contudo, as áreas não são consideradas fisicamente degradadas. Os valores de densidade máxima do solo foram de 1,91, 1,93, 2,00 e 2,03 Mg m-3, e os de estoque de C do solo, de 17,8, 16,6, 12,8 e 12,1 Mg ha-1, para mata nativa, pastagem, mandioca e cana-de-açúcar, respectivamente.

Understanding and quantifying the impact of land use and soil management on soil organic carbon (SOC) levels and physical properties is essential for the development of a sustainable agriculture. The purpose of this study was to evaluate some physical properties and SOC of an Oxisol in the Northwest of the state of Paraná, under different use and soil management systems, i.e., under native forest, pasture, cassava, and sugarcane. Disturbed soil samples were collected for particle size, particle density, proctor and organic carbon analyses and undisturbed samples (rings) to determine bulk density (Ds) and soil porosity. Results indicated that the land use and management systems induced changes in the soil physical properties in comparison to native forest. This was inferred from the higher values of soil Ds, maximum bulk density, and relative bulk density, and the lower values of macroporosity, total porosity, SOC and soil carbon stock, in the following growing order: pasture, cassava and sugarcane. However, the areas are not considered physically degraded.