818 EXPERIMENT STATION EECORD. 



is followed by sandy soil, while it is greater for humus and clayey soils. The 

 difference of behavior toward the rays of the two invisible ends of the spectrum 

 is greatest in dry clayey soil. While this absorbs ultraviolet light very readily, 

 it absorbs very little infra-x'ed light." 



Soil temperatures, J. W. Leather (Mem. Dept. Agr. India, C'hem. Scr., 4 

 {1915), Ko. 2, pp. 19-84, pis. 8, figs. 7). — Two years' observations on the 

 temperature of cropped and fallow alluvial soils at Pusa containing a high 

 proportion of calcium carbonate are reported. The temperatures were taken 

 by means of self-registering thermometers placed horizontally in the undis- 

 turbed soil at depths of 1, 2, 3, G, 9, 12, 18, and 24 in. 



It was found that the temperature of the surface soil varied naturally with 

 the hour of the day and with the season, the seasonal variations being mini- 

 mum in .January and maximum in May. In bare fallow soil " the diurnal 

 change of temperature extends to between 12 and 24 in. from the surface on 

 most days in the year. At 12 in. it amounts to about 1° C. but at 24 in. it is 

 doubtful whether it ever exceeds 0.1° in Bihar and probably does not exceed 

 0.2° in any part of India. 



" There is a fairly close correspondence between the temperature of bare 

 fallow soil at 1 in. from the surface and that of the air in the shade. Ap- 

 proximately the soil minimum at this depth is about 2° higher than the air 

 minimum, and the soil maximum is about 3° higher than the air maximum. 

 There is also a similarly close relation between the diurnal change of tem- 

 perature in the soil (bare fallow) at 1 in. from the surface and in the air 

 (shade), the diurnal change being about 1.5° greater in the soil at this depth 

 than in the air. This diurnal change is least during the monsoon and great- 

 est during the dry season. At the former season (June to September) it isnbout 

 10° in the soil (bare fallow) at 1 in. deep, and during the latter (in March 

 and April) it frequently approaches 20°. 



"Tlie temperature of the soil near the surface (down to 3 or 4 in.) is above 

 the mean temperature for only about 8 hours daily, while it is below it for 

 about IG hours. Tlie lag in temperature is about 2 hours at 3 in. deep and 

 about 8 hours at IS in. from tlie surface. A diange in the specific heat of the 

 soil, due to change of moisture content, does not seem to affect the maxima or 

 minima ; but rainfalls during the dry season, causing a considerable change in 

 the anK>unt of water evaporating, have a marked effect. . . . 



"The effect of a covering crop on the soil temperature is very marked, for it 

 both prevents the surface soil from rising to the temperature which fallow land 

 assumes and also modifies the diurnal change. Tluis while the temperature 

 of exposed soil at 1 in. deep rises to about 3° above that of the air, that of 

 cropped land is about 2° below it, and while the temperature of exposetl soil 

 at the surface rises to prol)id)ly some 20° above that of the air, the correspond- 

 ing figure for cropped land is only some 2 or 3° even in March, while in the 

 rains it is actually lower than that of the air. Also in respect of diurnal 

 change, at 1 in. deep, while exposed soil suffers a change of some 20° in March, 

 that of cropped land is only about 13° at the same depth, and during the mon- 

 soon, while exposed soil suffers a diurnal change of some 10° at 1 In. deep, 

 that of cropped land is only about 3 to 4°." 



Droughts, rainfall, and soil erosion {Union So. Africa Senate, 4- Sess., 1. 

 Parliament, 1914, .June 19, pp. XII-\-55-\-XXVIII, pis. 2).— This is a report 

 of an investigation by a conunittee of the senate of the Union of South Africa 

 regarding the occurrence and variation of rainfall in South Africa, the causes 

 and extent of soil erosion, and the drying up of certain areas in the Union, 

 with suggestions of possible remedial measures. 



