Indicadores da qualidade do solo em uma cronossequ?ncia sob sistema plantio direto em Gua?ra - PR

• Autor(a) principal: Ferreira, Cl?udia dos Reis
• Data de Publicação: 2016
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/2457
• topic: Mat?ria org?nica do solo; Agrega??o do solo; Invertebrados do solo; Soil organic matter; Soil aggregation; Soil invertebrates; Agronomia

To manage properly the natural resources and also to produce with sustainability is a big challenge. Conservation management practices, such as no-tillage system (NTS), intend to increase the sustainability of agricultural systems through improvement of chemical, physical and biological soil attributes. This work was developed in private rural systems, explored commercially in Guaira municipality ? Paran? State. Three different areas were evaluated, with NTS adoption time of 7, 14 and 23 years, with succession of soybean (summer) and corn/wheat crops (winter) (NTS7, NTS14 and NTS23, respectively), and an area of Atlantic Forest as reference. The sampling was taken in the dry season (September/2013), after harvesting corn, and in the rainy season (February/2014), after harvesting soybean; to evaluate effect of duration of soil usage and management under the different crops in NTS on edaphic attributes. The hypothesis tested were: a) long duration management systems can change physical, chemical and biological soil properties; b) the crop succession with grass/legumes species (corn/soybean) promotes modifications in the groups of soil macrofauna and, consequently, in the compartments of soil organic matter (SOM); and c) the season of sampling (winter and summer) influences the composition of soil macrofauna and in the SOM compartments. They were analyzed chemical attributes and total organic carbon (TOC) and nutrient stocks (Ca, Mg, K and P), particle size, aggregates stability, bulk and particle densities, actual soil moisture, calculated the total volume of pores, and evaluated the edaphic macrofauna, at the depths of 0-0.1, 0.1-0.2 and 0.2-0.3 m. The morphological types of aggregates were identified, establishing three groups: physiogenic, intermediates and biogenic. For the different groups it was measured the relative composition, TOC, and physical and chemical fractionation of organic matter. In general, the variation in chemical properties were related to NTS time and the sampling season, which also reflects the soil coverage. Soybean and corn/wheat succession contributed to increase contents and stocks of carbon, Ca and P in the different NTS chronosequences. Although there was no significant difference between the areas, the increasing bulk density values observed with depth in the NTS23 area, with longer system adoption, indicate compacted layers that should be monitored. The highest density and total richness of macrofauna individuals were found in the NTS14 and NTS23 areas under corn residues, but there were not observed higher indexes of equability, due to dominance of Formicidae and Isoptera groups. The areas with the highest equability values were the reference, in the dry season, and NTS23 in the rainy season, with values to 0.87 and 0.61, respectively. The biogenic aggregates were found in larger proportion in the reference area, while the physiogenics and intermediate predominated in the managed areas. The TOC contents were higher in biogenic aggregates, as well as organic carbon associated with minerals (OCam). The humin fraction showed no significant differences in the dry season, while in the rainy season the humin content was higher in physiogenic aggregates. This result indicates that biogenic aggregates of the dry season change into the physiogenic aggregates found in the rainy season.