Variability of CO2 emission and soil attributes in pasture and silvopastoral system

Author(s)

Deise Cristina Santos Nogueira

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2021-09-16.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2021-06-28
• Advisor: Alan Rodrigo Panosso; José Marques Júnior

Abstract

Agricultural practices interact with soil formation factors and processes to influence carbon dynamics and soil CO2 emission rates. Conservation systems can leverage this relationship to meet global food production requirements while reducing CO2 emissions, thus ensuring global food security in a sustainable way. This study aims to evaluate the carbon dynamics in areas of degraded pasture and silvopastoral system with different textures and mineralogical composition. The study was conducted in areas of degraded pasture and silvopastoral system located in Selvíria - MS, Brazil. Measurements of CO2 emission, temperature and soil moisture were conducted from May to October 2018 to study the temporal and spatial variability of these variables. Deformed and undisturbed soil samples were collected in the 0.00 - 0.10 m and 0.30 m - soil layer to perform physical and chemical soil analyses. The data were analyzed by classical statistics, geostatistics and simple multifractal analysis and joint multifractal. The results showed that CO2 emission differed between the study areas. The highest values of soil moisture and CO2 emission were observed in the silvopastoral system throughout the evaluation period, however the soil temperature was not different between the study areas. The spatial variability of CO2 emission, soil temperature and moisture was more homogeneous in degraded pasture. The higher clay contents and higher concentration of iron oxides observed in the silvopastoral system resulted in lower carbon losses, since carbon remained longer in the soil, thus resulting in a higher carbon stock in this area in relation to degraded pasture. Moreover, in this system, there was a higher insertion of organic material, since the degree of humification of organic matter was lower in relation to degraded pasture. In the silvopastoral system, the carbon stock and the degree of humification of organic matter showed greater spatial variability in relation to degraded pasture. CO2 emission showed different behavior at different scales in the two study areas. CO2 emissions and soil attributes presented similar processes at different scales. The inclusion of soil texture and mineralogy combined with the adoption of more conservationist agricultural practices helped in the better understanding to identify which agricultural areas presented the highest capacity to stock carbon in their soils, thus becoming allied in the reduction of soil CO2 emissions. Thus, soil with higher clay and mineralogy content with a higher predominance of iron oxides combined with higher addition of organic material and little soil revolving such as the silvopastoral system tended to be carbon accumulators, reducing carbon losses via CO2 emissions in the soil. (AU)

• FAPESP's process: 17/17532-6 - Clay mineralogy to estimate and mapping the CO2 emission in the Cerrado of Mato Grosso do Sul region
• Grantee: Deise Cristina Santos Nogueira
• Support Opportunities: Scholarships in Brazil - Doctorate