Emissão de gases de efeito estufa em arroz irrigado em várzea tropical
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2018-05-28
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Universidade Federal de Goiás
Resumo
The flooded rice crop (Oryza sativa L.) emits both N2O and CH4, which can contribute significantly to total greenhouse gas (GHG) emissions. Application of nitrogen fertilizers is normally necessary to achieve optimum yields, however over application may increase the risks of pollution and N2O and CH4 emissions in flooded rice system. A study in field conditions was carried out at the Palmital Farm, Embrapa Experimental Station Rice and Beans, in Gleysol Haplic, in order to verify the greenhouse gas emissions, the carbon stock and the physical properties of the soil in a system of production of flooded rice in tropical lowlands under different sources and doses of N. The treatments resulted from the factorial combination: (common urea (UC) and protected urea (UP)), and three nitrogen doses (30, 70, 150 kg ha-1) plus the control. Unformed and deformed soil samples were collected at depths 0-5; 5-10; 10-15; 15-20; 20-30; 30-40 and 40-50 cm, to determine the physical properties of the soil. Gas collection was carried out in the 2014/2015 harvest, in the off-season 2015, and in the 2015/2016 harvest. The concentrations of N2O and CH4 were determined by gas chromatography. For the determination of nitrate (NO3-) and ammonium (NH4 +) in the non-flooded period, soil samples were collected, soil solutions were collected in the flooded period, Eh and soil pH were determined. Nitrogen management affected the physical quality of Gleysol Haplic studied, but did not interfere in the productivity of flooded rice. The carbon and total nitrogen stocks decreased as the depth increased in the soil profile, with an increase in the layer of 10-20 cm. The results indicate that N2O fluxes remained low, regardless of applied N rates, when the soil was flooded, but they showed emission peaks in the non-flooded period, especially after precipitation or in the drainage period for the rice harvest. For the CH4 emissions the highest flows occurred at the end of the vegetative stage (growth) of the rice and after drainage when the soil was low aeration. The N2O and CH4 fluxes did not present a linear relation with the NH4 +, Eh and soil pH values. Emissions of N2O and CH4 did not show significant differences between sources and doses of N. Emissions of N2O increased with the incorporation of green manure, while CH4 emissions were potentiated with the incorporation of rice crop residues. The 64 kg ha-1 dose presented the best efficiency of N fertilizer to cultivate BRS Catiana with the lowest emission intensity.
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Oryza sativa , Física do solo , Inibidor , Óxido nitroso , Metano , Oryza sativa , Soil physics , Inhibitor , Nitrous oxide , Methane
Citação
MASCARENHAS, Y. S. Emissão de gases de efeito estufa em arroz irrigado em várzea tropical. 2018. 121 f. Tese (Doutorado em Agronomia) - Universidade Federal de Goiás, Goiânia, 2018.