EXPERIMENT STATION BULLETINS. 



451 



soils which have been cropped for about seventy years without the return 

 of much fertilizing materials, and the corresponding virgin or uncropped 

 soils. Such tests of course show wide variation in the changes in conipo- 

 tition of soils from different farms. In some instances they are negli- 

 gible; in case of others as much as sixty per cent of the phosphorus of 

 the surface soil has been removed, while forty per cent losses are com in on. 

 Later on-the effect of different systems of farming or the changes in the 

 composition will be reported. 



TABLE 3.— THE PHOSPHORUS BALANCE ON A 90 ACRE "MIXED" FARM WHICH 

 CARRIES 6 COWS. 4 CATTLE, 14 HOGS AND 5 HORSES. 



Loss in process of digestion and handling 



of manure, 40 per cent 134 . 6 



201.8 



phosphorus returned to soil in 201.8 

 manure. 



Total phosphoriis returned to soil 265 . 1 

 Total phosplirus lost from farm, 478 . 1. 

 Pounds of 16 per cent acid phosphate needed|toImakeIgoodIthe loss,[6,830. 



PJiospliorus in Some Michigan Soils. The phosphorus content of Mich- 

 igan's soils varies. The members of the Soils Section have been engaged 

 in a systematic study of the representative soils of the State. In addition 

 to other investigations, the composition of the samples collected has been 

 determined. The results, thus far obtained, that bear upon the phos- 

 phorus situation are set forth in Table 4. The phosphorus content of the 

 representative soils of Berrien, Cass, St. Joseph, Branch, Van Bureu, 

 Allegan, Newaygo, Mason, Manistee, Ingham counties and the Old Lake 

 Bed of Eastern Michigan is given. 



