Effect of soil solution viscosity induced by biopolymers on CO₂ emissions and soil attributes

The viscosity of the soil solution affects microbial activity and, consequently, soil CO₂ emissions. This study sought to assess the impact of soil solution viscosity, induced by different biopolymers, on soil CO₂ emissions and soil attributes. Four treatments (15 L) were applied to 1 m² plots of a Red Latosol lacking vegetation cover: a control (water) with a viscosity of 0.0318 Pa·s, and three solutions prepared with guar gum (GG), xanthan gum (GX), and hydroxyethyl cellulose (HEC), all adjusted to the same viscosity (0.03660 Pa·s), corresponding to a 20% increase relative to the control. Soil CO₂ emissions (FCO₂) were monitored over 30 days using an automated portable system (LI-8100, LI-COR Environmental). Simultaneously, soil temperature and moisture were monitored using a digital thermometer and a portable time-domain reflectometry (TDR) system. Treatments with GX and HEC exhibited significantly lower CO₂ emissions (p < 0.001), with mean values of 1.16 ± 0.09 and 1.36 ± 0.09 µmol CO₂ m⁻² s⁻¹, respectively, compared with the control and GG treatments (1.63 ± 0.09 and 1.81 ± 0.09 µmol CO₂ m⁻² s⁻¹, respectively). In addition, GX and HEC increased soil moisture, while soil temperature exhibited only minor variations among treatments. Overall, the results demonstrate that increasing soil solution viscosity using GX and HEC may regulate soil CO₂ emissions through changes in soil moisture and temperature.