PHYSICAL INTER-RELATIONS IN SOILS 51 



acre in twenty-four hours. 1 The averages of these losses 

 from very wet soils exceed that from normally moist 

 soil mentioned above, by over 20 tons to the acre for 

 twenty-four hours. In the conversion of this amount 

 of water into vapor-, heat was rendered latent sufficient 

 to raise an acre-foot of loam soil, with its normal 20 per 

 cent of capillary water, by 24.16 F. Curve F in Fig. 15 

 shows the temperature effects of the heat here involved if 

 applied to one acre-foot of soil of varying water content, at 

 a temperature of 32 F. When a saturated condition of 

 soil exists through a considerable period, the losses of heat 

 are practically multiplied by the days of the period. It 

 should be borne in mind, however, that if these losses were 

 prevented, not all the heat thus conserved would be 

 stored in the soil ; for there are other factors involved that 

 limit the rise of soil temperatures. These factors, never- 

 theless, would permit a very considerable rise of tem- 

 perature; indeed they would permit an approximate 

 approach to optimum conditions which cannot take place 

 while such losses occur from evaporation of gravitational 

 water. The figures are given especially to call attention 

 to the tremendous misdirection of the heat supply under 

 the conditions indicated. 



74. The effects of gravitational water upon temperature 

 through bad soil structure. Mention has already been 

 made of the serious extent to which puddling may take place 

 in clay and loam soils that remain, even for a relatively 

 short time, in a saturated condition (paragraphs 67 and 68), 

 and of the effects of such physical condition upon crops 

 planted in such soil, and of the large amount of labor re- 

 quired to reduce the lumpy condition after plowing. 



1 Report Wise. Exp. Station, 1891, p. 100, and Report Wise. 

 Exp. Station, 1890, p. 149. 



