A METHOD FOR MEASURING CARBON DIOXIDE EVOLUTION FROM SOIL

Abstract

The method described is suitable in greenhouse plots and under field conditions. The apparatus consists essentially of a galvanized iron collecting box, a suction device and an absorption train. From the collecting box the air is removed by suction as it diffuses from the soil, and is carried into an absorbing unit. The absorption train consists of 4 bottles; the 1st and 4th are empty to serve as safeguards; the 2nd and 3rd are filled with 0.16 N KOH. A suitable rate of flow is about 10 1. of gas per hr. The KOH solutions are titrated with HC1 after the addition of an excess of CaCl2. Corn and soy beans turned under as green manure give a marked increase in CO2 evolution over that of fallow soil. Moisture conditions play an important part in each case. Rainfall is followed by a marked increase in evolution of CO2, if the H2O of the soil is below optimum.