Crop succession and rotation in the no-tillage system: implications for soil CO2 emission and soil attributes

Author(s)

Clariana Valadares Xavier

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2019-02-25.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2018-12-05
• Advisor: Newton La Scala Júnior

Abstract

In agricultural areas, soil CO2 emission (FCO2) is a process due to the interaction of several factors, such as soil and climate conditions. The adoption of soil and crop management practices determines the intensity of this process. Although the effects of agricultural activities on FCO2 have been reported in several studies, few of them jointly assess the effect of physical, chemical, and biological soil attributes on FCO2 under a no-tillage system established for more than 16 years. Thus, the hypothesis of this study is that summer and off-season crops under the no-tillage system, when providing different residual inputs, affect soil attributes, reflecting on FCO2 variability. The experiment was carried out in strips with three replications. Treatments consisted of crop residues from three summer crop sequences (soybean-corn rotation, corn monoculture, and soybean monoculture) with five off-season crops (corn, sorghum, crotalaria, pigeon pea, and millet). At the end of harvest, FCO2, soil temperature (Tsoil), and soil moisture (Msoil) were assessed over a period of 51 days. Subsequently, soil samples were collected at depths of 0–0.10 and 0.10–0.20 m for determining the physical, chemical, and biological soil attributes. The multivariate analysis showed that the characterization of the pattern of FCO2 and other soil attributes, as a function of the management with summer and off-season crop residues, differed according to the analyzed soil layer. In the 0.10-0.20 m layer no difference was observed between the studied treatments. However, the contents of clay, organic matter, the sum of bases, microbial biomass carbon, dehydrogenase and amylase enzyme activity, and the humification index of organic matter in the most superficial soil layer (up to 0.10 m), contributed to characterize the differences in FCO2. Thus, the variation in FCO2 is more influenced by microbiota and the management in the most superficial soil layer. When the temporal variation of FCO2, Tsoil, and Msoil was analyzed, we observed for FCO2 a significant effect of the interaction between time and summer crop sequences (F = 1.44; p = 0.02), and time and off-season crops (F = 2.26; p <0.01). For Msoil (F = 1.83; p < 0.01) and Tsoil (F = 1.32; p = 0.01), a triple interaction was observed between summer crop sequences, off-season crops, and time. The temporal variation of FCO2 was related to its higher sensitivity to changes in Msoil regardless of the assessed management. However, no significant relationship was observed between FCO2 and Tsoil. Therefore, management systems under no-tillage are more balanced, i.e. less prone to sudden changes in their physical, chemical, and biological conditions. Thus, the average daily values of FCO2 tend to be stable, and variations in gas dynamics over time is given only under precipitation conditions and its effect on the soil moisture and pore ratio. (AU)

• FAPESP's process: 15/26289-2 - CO2 EMISSIONS ASSOCIATED WITH SOIL ATTRIBUTES AND RESIDUES OF SUMMER SEASON AND OFF-SEASON CROPS IN AREAS UNDER NO-TILLAGE
• Grantee: Clariana Valadares Xavier
• Support Opportunities: Scholarships in Brazil - Doctorate