Carbono no solo em sistemas integrados de produção agropecuária no Cerrado e na transição Cerrado - Amazônia

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Universidade Federal de Goiás


Integrated crop-livestock (iCL) and integrated crop-livestock-forest (iCLF) systems are pointed out as potential soil carbon sinks. However, there are few scientific studies that evaluated the real contribution of these production systems. This work included two studies. The first was to evaluate soil carbon accumulation and its origin in iCLF in the transition zone of the Cerrado-Amazon biomes; the second aimed to calibrate and validate the CQESTR model for the Cerrado ecosystem and to evaluate the effect of soil management practices, including iCL and various scenarios on soil organic carbon (SOC) over time. For the first study two areas under iCLF (iCLF1 and iCLF3, with one and three rows of Eucalyptus urograndis by hedgerow, respectively) were selected. They were cultivated in this system since 2009 in Nova Canaã do Norte, MT. A continuous pasture was used as reference. Soil samples were taken from eight layers (0.0 to 1.0 m) for the evaluation of the bulk density, texture, total C and N and δ¹³C. The second study was conducted in the Cerrado biome. The evaluated areas (Paddock 4 - P4 and Paddock 5 - P5 has been being managed in iCL since 2000. Bulk density and the organic matter content were determined for the 0.0-0.1 and 0.1-0.3 m layers. The CQESTR is a process based model which simulates the effect of climate, crop rotation and tillage management practices on SOC. The model was calibrated with P5 data and validated with P4 data. Its performance was evaluated using statistical regression analysis and the root mean square deviation (MSD). For the first study, the soil C stocks and isotopic composition were affected by the implementation of the iCLF system. The forest component was an important factor for soil C accumulation for both areas under iCLF. The N can be a limiting factor for C accumulation. We concluded that iCLF affected soil C and N stocks in the short term, however, longer iCLF deployment time would be necessary to elucidate the impact of iCLF in the long-term. In the second study model calibration was performed by adjusting the basic decomposition rate coefficient. The measured and simulated values were significantly correlated with an MSD of 2.11, indicating that the model captured spatial-temporal dynamics of SOC in the topsoil. However, CQESTR underestimated SOC for the 0,1-0,3 m layer, probably due to lack of site specific grass or crop root biomass and distribution data under tropical conditions. Additional calibration is required to improve prediction of SOC stabilization process in the subsoil layers of tropical soils. In the long term (20 years), for the superficial (0,0-0,1 m) soil layer, the model simulated C accumulation in iCL and C loss in soybean/corn grain production system independently of the use of zero-tillage or conventional tillage in either of these systems under Cerrado conditions.



OLIVEIRA, J. M. Carbono no solo em sistemas integrados de produção agropecuária no Cerrado e na transição Cerrado - Amazônia. 2015. 90 f. Tese (Doutorado em Agronomia) - Universidade Federal de Goiás, Goiânia, 2015.