316 soils: PBOPEBTmS AND MANAGEMENT 



conditions is effective in bringing about any important 

 modification of soil temperature it is often difficult to 

 decide. In greenhouses and hotbeds perceptible increases 

 are obtained by the use of large quantities of fresh manure, 

 as high an increase as 75 degrees Centigrade has been 

 observed under such conditions. In the field, however, 

 where the absorption and radiation of heat are very large, 

 where the organic matter makes up only a fraction of the 

 soil's components, and where the applications of barnyard 

 manure are relatively small compared to the bulk of the 

 soil, it is doubtful whether any important increase of 

 soil heat actually occurs. Georgeson,^ working in Japan 

 with varying quantities of manure, obtained during the 

 first twenty days an excess over the check of only 3.4 

 degrees Fahreniieit from an application of eighty tons an 

 acre. With twenty tons the increase was 1.7 degrees. 

 Wagner^ obtained similar results, finding an average 

 excess of 1 degree Fahrenheit from the use of twenty 

 tons of barnyard manure. Bouyoucos ^ has obtained the 

 latest data on this subject. Under controlled laboratory 

 conditions he found that unless excessive amounts of 

 manure were applied no appreciable effects were observed. 

 With an application of ten tons the highest rise was one- 

 half degree Centigrade; after one hundred and three 

 days the manured soil was only one-fourth degree higher 

 than the untreated. Such results show that the heat of 

 fermentation has little important practical influence 



1 Georgesoa, C. C. Influence of Manure on Soil Tempera- 

 ture. Agr. Sci., Vol. I, pp. 25-52. 1887. 



2 Wagner, P. tJber den Einflnss der Diingung mit Organ- 

 ischen Substance auf die Bodentemperatnr. Forsch. a. d. 

 Geb. d. Agri.-Physik, Band V, Seite 373-405. 1882, 



^Bouyoucos, G. J. An Investigation of Soil Temperature. 

 Michigan Agr. Exp. Sta., Tech. Bui. 17, pp. 180-190. 1913. 



