AND COLLEGE, PUSA, FOR 1914-15. 15 



The information has been published as a Memoir of the 

 Department of Agriculture in India (Chemical Series, 

 Vol. IV, No. 2) and the principal items of information are 

 as follows : — 



(a) In bare-fallow soil, (i) There are naturally both 

 diurnal and seasonal changes of temperature. 

 The former extends to between 1 ft. and 2 ft. 

 from the surface; at 1 ft. deep it amounts about 

 1° C, but at 2 ft. it is doubtful whether it ever 

 exceeds 01° C. in Bihar and probably never 

 exceeds 0-2° C. in any part of India. Near the 

 surface the diurnal change is very considerable. 

 The seasonal change at 2 ft. deep amounts to 

 about 13° C. The minimum temperature occurs 

 in January and the maximum in May. 



(ii) There is a fairly close correspondence between the 

 soil temperature at 1" deep, in bare- fallow soil, 

 and the air (shade) temperature; approximately 

 the soil-minimum is 2° higher and the soil- 

 maximum 3° higher than the air temperature. 

 (iii) There is a similar relation between the diurnal 

 change of temperature in the soil and air; at 

 1" deep this change is about 1-5° C. greater in 

 the soil than in the air. This diurnal change 

 is least during the monsoon and greatest during 

 the dry season, as is the case in the air. The 

 amount of the change varies from 10° C. to 

 20° C. 



(iv) Regarding the soil-temperature at the surface 

 this could not be ascertained directly, but judg- 

 ing by collateral evidence, with a clear sky it 

 probably rises to about 20° C. higher than the 

 air (shade) maximum temperature during the 

 day, and falls to approximately the air mini- 

 mum at night. 



(v) The above relations are substantially independent 

 of season, and since the range of temperatures 

 at Pusa is considerable, it seems reasonable to 



