Ciniro Costa Junior

Emissão de gases do efeito estufa em diferentes usos da terra no bioma Cerrado

The conversion of native forests by cutting and burning into farming areas leads to alterations in the dynamics of soil organic matter, with changes in emissions of greenhouse gases (GHGs: CO2, CH4 and N2O) from the biosphere to the atmosphere. These cause an average temperature rise and, consequently, global climate change. The aim of this study was to examine relationships between the fluxes of CO2, CH4 and N2O with moisture, microbial biomass and inorganic N forms in soil with different land uses in the Cerrado biome (Rio Verde county, State of Goias - Brazil). The climate (Koppen-Geiger) was classified as Aw and the soil as Latossolo Vermelho distrofico caulinitico / a clayey kaolinitic Oxisol under original Cerrado (Brazilian savanna) vegetation. The experiment was arranged in a completely randomized design (CRD) with four treatments (areas): Native vegetation - Cerrado (CE); brachiaria pasture (PA); soybean in conventional tillage (SC) and no-tillage (NT) corn followed by millet. No significant differences in annual CO2 and N2O emissions were observed between treatments. This can be explained by the variability of gas fluxes due to climate seasonality, with lower emissions in the winter due to low soil moisture. Mean emissions of CO2 were 108.9 ± 85.6 mg m-2 h-1 , and of N2O 13.5 ± 7.6 mg m-2 h-1 . For CH4 significant differences in the fluxes were only observed in pasture (32 mg m-2 h-1 ), while in the other areas inflows between 46 and 15 mg m-2 h-1 were observed. The GHG fluxes showed close correlation with soil moisture. The N-NO3- emissions were significantly correlated with CO2-emissions in all areas. Considering all treatments together, the three GHG fluxes were correlated with the microbial C and N contents. However, the Cmicro: Nmicro ratio was not significantly correlated with the GHG flux. Only for pasture the CO2 and N2O fluxes were correlated with the content of soil inorganic-N. Results suggested that the GHG fluxes in the Cerrado are related to rainfall, mainly in farming areas treated with high fertilizer doses to increase productivity.

Carbono total e δ13C em agregados do solo sob vegetação nativa e pastagem no bioma cerrado

Different management systems affect soil C, however decreases in the C stocks of native Cerrado areas converted to pasture have been reported. This calls for further research on this trend, under different management systems and soil-climatic conditions. The objective of this study was to evaluate soil aggregation, C levels and natural abundance of δ13C in a 20 year-old pasture (PA), following nine years of cropping, with signs of degradation compared to soil under native Cerrado (CE) in an adjacent area. The studied areas are located in Rio Verde, state of Goias (Brazil), with soil classified as clayey Oxisol. In samples from the layers 0-5, 5-10 and 10-20 cm the distribution of water stable aggregates (microaggregates, mesoaggregates and macroaggregates), mean weight diameter (MWD) and mean geometric diameter (DMG), C contents and δ13C, the mean residence time of C (TRM), and the free light fraction of organic matter (FLL) were determined. Results indicated that grazing after cropping reduced the original C stock by 21 %, possibly due to a lower FLL input. Soil showed high aggregation and no significant difference between the assessed areas was observed. However, C levels in macroaggregates were lower in PA compared to CE, while in microaggregates C was not affected, suggesting, respectively, greater and lower sensitivity to management and lower and greater protection of C by these aggregate classes. Values of TRM and isotopic abundance reinforced these findings, showing a replacement of 83 % of the original C after crop and pasture cultivation for 29 years. A constant application of plant residues to the soil surface as well as C maintenance within macro and mesoaggregates are essential factors to ensure C accumulation in this soil type.

EMISSÃO DE GASES DO EFEITO ESTUFA E SUSTENTABILIDADE: UMA PERSPECTIVA DO SISTEMA DE PRODUÇÃO DE CARNE BOVINA NO BRASIL

The greenhouse gases emission (GHG) is a common subject debated today. Countries with reduction targets on greenhouse gas emissions have developed studies to understand the processes and reduce emissions. Deforestation and cattle make Brazil one of the largest emitters of GHG. Among the main products of Brazilian agriculture is beef cattle, handled mainly in the extensive system, where animals are slaughtered at an average of three to four years and receive little or no pasture tract culture. Another system in use in Brazil is the semi-extensive, where cattle finishing phase is under feedlot under a diet especially designed for fattening. Quantification and monitoring of GHG emissions in agricultural systems allow the assessment of the impact on the environment. This review will discuss the main sources of GHG emissions in livestock and guidelines necessary to evaluate the research of alternative sustainable beef production systems.