652 



STATE BOARD OF AGRICULTURE. 



the usual manner. The quantity of gas given off was taken as a meas- 

 ure of the amount that would be absorbed at the same temperature 

 since expulsion is the reciprocal of absorption. Attention must be 

 called here, however, to the fact that the porosity of the material comes 

 into play and consequently not all of the gas given off or taken up 

 at the various temperatures, is du^e to absorption. The soils employed 

 were the same as those in the preceding series of experiments. The 

 results obtained are detailed herewith. 



TABLE 13.— EFFECT OF TEMPERATURE ON ABSORPTION OF GASES. 



Sou. 



Quartz sand . . , 



Sandy loam 



Clyde silt loam 



Clay 



Peat 



Dry wt. 

 of soils. 



202.5 

 221.6 

 164.5 

 182.5 

 92.0 



Capacity 

 of tube. 



152 

 152 

 152 

 152 

 152 



0-10°C. 

 c. c. 



3.3 

 3.9 

 5.0 

 4.8 

 6.1 



10-20°C. 

 c. c. 



2.8 

 3.6 

 4.3 

 4.4 

 5.4 



20-30°C. 

 c. c. 



2.8 

 3.0 

 4.2 

 4.2 

 5.0 



30-40°C. 

 c. c. 



2.8 

 3.0 

 4.0 

 4.1 

 4.9 



40-50''C. 

 c. c. 



2.5 

 2.6 

 3.6 

 3.8 

 4.5 



Total 

 c. c. 



14.2 

 16.1 

 21.1 

 20.30 

 25.9 



It will be seen from the above table that the amount of air given 

 off (or absorbed), decreases regularly and gradually with temperature. 

 It will also be observed that the total quantity is greatest in peat and 

 decreases with Clyde silt loam, clay, sandy loam and quartz in order 

 respectively. 



From these results it is evident that absorption of gases by dry soils 

 influences the aeration of soils principally at the lower temperatures and 

 that at the higher temperature it is the aqueous vapor which plays the 

 most important and greatest role. 



It should be mentioned, however, in passing that a certain amount of 

 the gases expelled from moist soil with the elevation of temperature is 

 due also to that absorbed by the soil water. How much of the total 

 volume owes its origin to this source it cannot be stated definitely as no 

 experimental work was performed on the subject, but probably it is com- 

 paratively very small. 



Thus we see that temperature has a tremendous influence upon soil 

 aeration and in a manner not heretofore altogether realized. It is true 

 that the diurnal temperature amplitudes are not very appreciable below 

 six inches, but above this depth, which constitutes that layer of soil most 

 tilled, they are very large, and especially in certain regions of the world. 

 Field experiments on soil temperature at this Station, which have been 

 running for four years, show that the diurnal fluctuation in temperature 

 in the different types of bare soil, is sometimes as high as 25® C. for 

 the first inch depth, 15° for the second, 13° for the third, 10° for the 

 fourth, 8° for the fifth, and 6° for the sixth, making an average of about 

 13° C. for the upper six inches. As a rule these fluctuations are larger 

 for the sandy soils and smaller for the muck and peat and still smaller in 

 cropped soils. During the warm part of the year there occurs very often 

 excessive hot and cold days only a short distance apart. The difference 

 between the maximum soil temperature of the excessively hot day and 

 the minimum soil temperature of the excessively cold day sometimes 

 amounts to 40° C. at the upper first inch of soil. On the other hand, it 

 must also be remembered that the soil temperature undergoes great 

 changes between summer and winter and the influence of temperature on 



