Abstract

                                Soil respiration in terms of carbon dioxide (CO2) evolution is a potentialbiological indicator to assess the soil quality as influenced by differentagricultural practices. However, the relation between the CO2 evolution andthe biological attributes of soil is a multitude and hence less resolved. Thepurpose of the study is to relate the measured CO2 values with the biologicalquality indicators of the soil. Four long-term nutrient management treatments(organic manure amended, OM, integrated nutrient management enforced,INM, synthetic fertilizer applied, IC, and unfertilized control, Control) from100-years old permanent manurial experiment was used for this study.The soils were analyzed for soil organic carbon, microbial biomass carbon,labile carbon, protein index, dehydrogenase activity, and substrate-inducedrespiration and calculated the soil biological quality index (SBQI) by quadrantplotmethod. All the soils were measured for the flush of CO2 immediatelyafter wetting the dry soil by three methods viz., alkali trap method, infra-redprobe-based flux apparatus, and multi-gas analyzer. The results revealedthat INM had a positive influence to improve all the six biological attributesfollowed by OM, while the IC and Control had at par levels of all the assessedvariables. The SBQI also has high resolution to discriminate against the soilsand INM > OM > IC ≈ Control is the order being observed. The CO2 evolvedfrom these four soils had a strong positive correlation with all the assessedbiological health indicators. The regression analysis revealed that SBQIhad a significant positive relation with alkali trap CO2 (R2 0.82), flux CO2 (R20.75), and multi-gas analyzer CO2 (R2 0.79). The present results suggestthat analyzing CO2 evolution could be a simple method to relate the overallbiological quality of the soil. Hence, developing a simple tool to measurethe soil CO2 evolution could help the farmers to know the biological qualityof the soil .

Key words : Soil health; Soil quality index; Biological indicators; Sustainable soil management