Soil CO2 emission (FCO2) in agricultural areas is a process that results from the interaction of different factors such as the climate and soil conditions. In addition, the adopted practices of soil and crop managements determine the intensity of this process. Although the effects of agricultural activities on the FCO2 are reported in several studies, there is still a lack of studies assessing the effect of soil physical, chemical and biological attributes on the FCO2 in a no-till system established for over 13 years. Thus, the hypothesis of this study is based on the fact that the summer season and off-season crops in a no-till system, by providing different residual contributions to the soil, affect the dynamics of the soil microbial activity, reflecting the variability of CO2 emission. The aim of this study is to characterize the soil CO2 emission and its relationship with soil attributes and residues of summer season and off-season crops in a consolidated no-till system. The study will be conducted in neighboring areas in an experiment initiated in 2002. The experiment will be accomplished in strips with three replications. The treatments will consist of the crop residues of three combined sequences of summer season crops (soybean-corn rotation, corn monoculture and soybean monoculture) with seven off-season crops (corn, sorghum, sunflower, sunn hemp, pigeon pea, oilseed radish and pearl millet). At the end of the harvest of those crops the FCO2, soil temperature and moisture will be evaluated over a period of 30 days. After the evaluations, soil sampling will be carried out at a depth of 0-0.20 m to determine the soil physical, chemical and biological attributes. The variability of the data will be analyzed using descriptive statistics, analysis of variance and linear regression. The variables behavior as a function of the crop residues will be evaluated by means of multivariate analysis of grouping and principal components.
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