EMISSÃO DE CO2 E ESTOQUE DE CARBONO NO SOLO NO DESENVOLVIMENTO INICIAL DE EUCALIPTO COM O USO DE HIDROGÉIS E IRRIGAÇÃO

Abstract

Understanding the influence of hydrogel use on CO2 emissions and soil carbon stocks during the early development of eucalyptus seedlings is relevant from both environmental and production perspectives. Studies in this field can provide valuable information for developing more sustainable management practices that combine forest productivity with carbon emission mitigation, thereby contributing to more resilient and environmentally responsible production systems. Thus, this study aimed to evaluate *in situ* soil CO2 emissions and initial and final soil carbon stocks during the early development of eucalyptus seedlings subjected to different hydrogel dosages and irrigation levels. For *in situ* soil CO2 emission (FCO2) assessments, the portable EGM-5 system (PP-Systems, Amesbury, USA), model AGA560, was used, with one pipe per experimental pot. A colorimetric method, following the recommendations of Cantarella et al. (2001), was employed to determine initial and final soil carbon stocks. Data were subjected to analysis of variance using Rbio software, and the evaluated variables were analyzed using the Scott-Knott test at a 5% probability level. Subsequently, a canonical variable analysis was performed to examine the interrelationships among CO2 flux, initial and final soil carbon stocks, and the different hydrogel dosages and irrigation levels. The use of hydrogels combined with different irrigation levels significantly influenced CO2 emissions and soil carbon stocks during the early development of eucalyptus seedlings. The hydrogels showed distinct responses regarding CO2 emission dynamics throughout the evaluation period, with behavior dependent on water availability. The cashew gum-based hydrogel (HGC) stood out by providing a higher final soil carbon stock, indicating greater potential for biomass accumulation and carbon retention. Treatments using the commercial hydrogel Hydroplan-EB (HCOM) and the babassu mesocarp-based hydrogel (HMB) exhibited higher CO2 emissions under specific irrigation conditions, particularly with higher irrigation depths. Overall, the interaction between hydrogel and irrigation proved to be a significant factor in the system's carbon dynamics, highlighting the potential of hydrogel use in the sustainable management of eucalyptus seedlings.