18 REPORT OF THE AGRICULTURAL RESEARCH INSTITUTE 



tions, and the more perfect one which has been employed 

 for recent investigations was only designed and made in 

 1913. By its aid the gases contained in a known volume 

 of soil taken from a specified depth below the surface can 

 be separated, measured and analysed. 



One of the first questions that occurs is whether a finely 

 divided material like a soil condenses much gas on its 

 surface. A volume of soil will include mineral and 

 organic matter, water and gases. The volume of soil in 

 the apparatus above referred to can be measured; the 

 volumes of the solid material, and of the water can be 

 derived from their weight and density, that of the gas 

 which is extracted can be measured. Some of the latter 

 will be in solution in the water, but the volume of this can 

 be calculated. Thus these various measurements yield on 

 the one hand the volume of the soil ; on the other the volumes 

 of solid material, water, gases. If there were no condensa- 

 tion of gas by the soil material, the sum of the latter would 

 equal the volume of the soil in situ. But if the soil mate- 

 rial is able to condense gases, the sum of the several consti- 

 tuents will exceed that of the soil. The measurements are 

 naturally accompanied by some errors and it is not possible 

 to say that the Pusa soil condenses no gas, but the propor- 

 tion is certainly very small and is less than 4 per cent, of 

 the total gas present. 



The amount of gas which the water in the soil dissolves 

 is of great interest. In dry land soils, the only gas which 

 dissolves to any material extent is carbon dioxide, the 

 volumes of dissolved oxygen and nitrogen being too small 

 to be of any consequence. By the aid of the work 1 on the 

 bicarbonates of calcium and magnesium which was done in 

 this laboratory by myself and Mr. Sen, it is possible to 

 calculate how much of the carbon dioxide is dissolved and 

 in the gaseous state in the soil respectively. In fallow soil 

 in all ordinary conditions very much the greater part of 

 the carbon dioxide is in the dissolved state. 



1 Mem. Dept. Agric. Ind., vol. I, no. 7, and vol. Ill, no. 8, 



