I<:o. 7. DEPARTMENT OF AGRICtJLTUUE. 497 



themselves throughout the glacial regions are not marked by any 

 special abundance of lime compounds. For this reason, the wash, 

 even when it forms a very considerable fraction of the cumulose soil, 

 rarely contains enough soluble lime to change materiall}^ the character 

 of these soils so far as concerns rhe supply of lime necessary for their 

 conversion into productive lauds, li js, as 1 have said, to their 

 nitrogen that their agricultural value is due. This element, present 

 to the extent of but .05 per ceur. in heavy clay subsoils, averaging 

 about .15 per cent, in good arable lands, and rarely exceeding .'J,b per 

 cent, in old meadows, amounts above 1 per cent, in these cumulose 

 soils and sometimes reaches two to three times that amount or even 

 more. Studies made at the [Station of the conditions in which this 

 nitrogen exists, show that the various beds so far examined ditfer 

 quite materially in their proportions of what is termed active humus ; 

 that is, of organic material capable of solution in dilute alkali, in 

 ordinary lands where the active humus is abundant it is believed 

 that the plant remains constituting the humus are in the highest de- 

 gree available for the support of succeeding crops. In the cumulose 

 soils most of the organic material is inactive, so that the nitrogen Is 

 especially resistant to the natural processes tending to make their 

 nitrogen available. In other cases, however, the proportion of active 

 humus is quite considerable, and included therein may be found an 

 important traction of the nitrogen content of these soils. 



(Several points concerning certain of the physical properties in 

 which the cumulose soils differ especially from the soils of other 

 classes, may be noted in this connection. Kespecting their heat rela- 

 tions, it should be observed that the soil temperatures are governed 

 by the comparatively large amounts of water these soils contain, both 

 when in their normal state and when best perpared for cropping. 

 Schtibler showed that, doubtless owing to their dark color as the 

 principal intiuential property, garden mould and humus soils attain, 

 when dry, higher temperatures upon exposure to the sun than do 

 other soils. This is because it takes less heat to raise the temperature 

 of humus than it does to increase those of clays, sand, etc. For 

 Ulrich has shown that the quantity of heat required to increase by 

 one degree the temperature of dry humus is about one-half that 

 necessary to cause a like elevation of temperature in equal weights 

 of clay, chalk, or sand. The power of these organic soils to transmit 

 or conduct heat from one point to another is also much less than that 

 possessed by the principal substances in mineral soils, as has long 

 been known and recently very carefully proven by Patten.* All these 

 data refer, however, to dry cumulose soils, and are of greater scien- 

 tific than practical value because, by reason both of the location of 

 these soils, their relation of bodies of water, their usually low lying 

 position with respect to surrounding lands, and also because of their 

 water requirements under cultivation, the cumulose soils are, in 

 practice, dealt with only in the moist condition. As a matter of fact, 

 these soils are cold, thaw out late, have a very short growing season, 

 and are especially subject to late spring and early fall frosts; their 

 common location near the foot of steep hillsides, renders them par- 

 ticularly open to the influence on quiet nights of cold air drainage, 

 which intensifies conditions otherwise favorable to frosts. 



Harrison E. Patten. Heat Transference in Soil. Bull. 59, Bureau of Soils U. S. D. A. 



32—7—1910 



