Application of Biopolymers in Soil: Impacts on CO₂ Emissions and Enzymatic Activity

Modifying soil solution viscosity with biopolymers has emerged as a strategy to reduce microbial CO₂ emissions. This study aimed to evaluate the effects of different biopolymers on soil enzymatic activity and CO₂ emissions. The experiment was conducted in lysimeters without vegetation cover, using Red Latosol and four treatments: control (water) (C0), guar gum (GG), xanthan gum (GX), and hydroxyethyl cellulose (HEC), with concentrations adjusted to exceed the control viscosity by 15%. CO₂ emissions were monitored for 32 days using a portable spectrophotometer (LI-COR Environmental, LI 8100). Enzymatic activity was measured using β-glucosidase and arylsulfatase activity at 1, 7, 14, and 21 days after application. The results indicated that soils treated with HEC (1.36 ± 0.09 µmol m⁻² s⁻¹) and GX (1.16 ± 0.09 µmol m⁻² s⁻¹) exhibited lower CO₂ emissions compared to the control (1.63 ± 0.09 µmol m⁻² s⁻¹) (p < 0.05). On day one, a decrease in β-glucosidase enzyme activity was observed in the GG (50.0 μg p-nitrophenol g⁻¹ soil h⁻¹) and GX (51.0 μg p-nitrophenol g⁻¹ soil h⁻¹) treatments compared to the control (62.5 μg p-nitrophenol g⁻¹ soil h⁻¹). The GG treatment (53.5 μg p-nitrophenol g⁻¹ soil h⁻¹) also showed the lowest β-glucosidase activity on day 21 compared to the rest of the treatments. GX treatment showed higher enzyme activity on day 14 compared to control for both arylsulfatase and β-glucosidase (29.5 and 54.0 μg p-nitrophenol g⁻¹ soil h⁻¹ respectively). However, on day 21, the highest enzymatic activity of arylsulfatase as well as β-glucosidase was observed in HEC (22.2 and 77.0 μg p-nitrophenol g⁻¹ soil h⁻¹). The application of GX and HEC can reduce soil CO₂ emissions and improve enzyme activity. These findings reinforce the potential of biopolymers as a strategy to mitigate carbon loss from soils, aligning with Sustainable Development Goal 13 related to climate action.