Colorimetric Quantification of CO₂ in a Modified Alkali-Trap Soil Respiration Assay
Durgesh Agase *
PMCoE, Govt. J.S.T.P.G. College, Balaghat, M.P., India.
Sheefa Khan
PMCoE, Govt. J.S.T.P.G. College, Balaghat, M.P., India.
Madhvi Bisen
PMCoE, Govt. J.S.T.P.G. College, Balaghat, M.P., India.
Harsh Tiwari
PMCoE, Govt. J.S.T.P.G. College, Balaghat, M.P., India.
*Author to whom correspondence should be addressed.
Abstract
Microbial activity in soil is an important characteristic of healthy soil. A key indicator of microbial activity is soil respiration. Traditional alkali-trap assays use hydrochloric acid to titrate sodium hydroxide that has not reacted to quantify CO₂ evolution, but determining the titrimetric endpoint is subjective, involves colour fading, reagent instability, and operator variability. The present study reports a modified soil respiration assay using colorimetric quantification of pH reduction as sodium carbonate forms. The method is phenolphthalein-based absorbance reading at 552 nm with a colorimeter. The alteration of the assay greatly improved precision, eliminated blank samples, and reduced human error from visual titration. This colorimetric method is easier, inexpensive, and provides reliable quantification of soil microbial respiration.
Keywords: Soil respiration, colorimetric analysis, CO₂ evolution, alkali trap, microbial activity