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| Author(s): |
Mara Regina Moitinho
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Jaboticabal. 2017-04-11. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal |
| Defense date: | 2017-03-02 |
| Advisor: | Newton La Scala Junior |
| Abstract | |
Although agriculture is an important emission source of CO2 to the atmosphere, soil use and management will coordinate the emission potential in agricultural areas. In this context, this study was carried out in sugarcane production areas and under two experimental field conditions. In the first condition, the aim was to characterize soil CO2 emission (FCO2) process in areas under mechanized unburned and manual burned sugarcane harvesting systems, as well as investigate the relationship between emission and soil attributes in both systems. Two neighboring areas with different harvest management systems were used: an unburned sugarcane (US) area, with large amounts of crop residues left on the soil surface after mechanical harvest, and a burned sugarcane (BS) area, with manual harvest after burning the sugarcane field and without crop residue on the soil surface. FCO2, soil temperature (Ts), and soil moisture (Ms) were assessed at 20 sampling points in each area with nine assessments over a period of 28 days. Subsequently, soil samples were collected at each point at a depth of 0–0.20 m to determine soil physical, chemical, and microbiological attributes. FCO2 in BS area (2.63 µmol m−2 s −1) was, on average, 37% higher than the emission measured in US area (1.92 µmol m−2 s −1). Temporal variations of FCO2 and Ms was correlated in US (R2 adj = 0.64; p<0.05) and BS (R2 adj = 0.66; p<0.05). Carbon stock, temperature, moisture, air-filled pore space, sum of bases, and abundance of functional genes related to carbon (pmoA) and nitrogen (nifH) cycles are the most representative soil attributes that helped to characterize CO2 emission process in soils under US and BS systems. In the second experimental condition, the aim was to characterize the spatial variability patterns of FCO2 and soil physical, chemical, and microbiological attributes in a sugarcane area after field reform activities. In this area, 10 measurements of FCO2, Ts, and Ms were performed in a regular 90 × 90-m grid containing 100 sampling points inserted in the area after field reform. Geostatistical analyses were performed for assessing the spatial variation and mapping soil attributes. After FCO2 mapping, two regions (R1 and R2) with different emission values were identified in the study area, in which was determined the abundance of 16S rRNA genes of Bacteria, pmoA, and nifH by quantitative real-time PCR (qPCR), in addition to other soil enzymatic activity analyses. The spatial patterns of FCO2 were similar to those of macropores, air-filled pore space, silt content, organic matter, and soil carbon decay constant. The results also indicated that the spatial pattern of FCO2 in the regions R1 and R2 may not be directly related to the total amount of microbial community (16S rRNA) in the soil, but to the specific function that these microorganisms play in relation to soil carbon degradation (pmoA). (AU) | |
| FAPESP's process: | 14/03634-3 - Spatial variability of CO2 emission associated bacterial communities and soil properties in area of sugar cane |
| Grantee: | Mara Regina Moitinho |
| Support Opportunities: | Scholarships in Brazil - Doctorate |