USE OF PHOSPHORUS IN DIFFERENT FORMS 245 



amount in 200 pounds would be sufficient to increase the yield of 

 corn by one bushel, while such an application would contain more 

 phosphorus than a hundred-bushel crop of corn. 



In Tables 37, 38, and 39 are recorded in detail the results of 

 the world's most important and complete investigation thus far 

 reported concerning the use and comparative value of raw rock 

 phosphate. These experiments were begun by the Ohio Agricul- 

 tural Experiment Station in 1897, and through the kindness of 

 Director Thorne the author is able to include twelve years' data in 

 these tables. 



In these experiments a three-year rotation of corn, wheat, and 

 clover has been followed on three separate tracts of land, so that 

 every crop may be represented every year. One plot in each series 

 receives 8 tons per acre of manure "taken from the open barn- 

 yard, where it has been accumulating during the winter," and 

 applied to the clover sod in the spring, to be plowed under for corn. 

 Another plot receives at the correct time 8 tons per acre of manure 

 " taken from box stalls, where it has accumulated under the feet 

 of animals kept continuously in the stalls." 



Two other plots in each series receive the same kind and quantity 

 of manure with each ton of which 40 pounds of fine-ground raw 

 rock phosphate have been mixed, and two other plots receive ma- 

 nure with each ton of which 40 pounds of acid phosphate have 

 been mixed. 



Every third plot in each tract or series receives no manure or 

 other fertilizer. 



In the tables are reported the yields of corn, wheat, and clover, 

 the experiment having been started in 1897 on section A, and in 

 1898 on sections B and C. Clover failed the first three years, and 

 in its place soy beans were grown, and they were plowed under. 

 The hay crop harvested in 1907 was soy beans, grown because of 

 clover failure. 



Chemical analysis and the results of other field experiments 

 show that the Wooster soil is most deficient in phosphorus, with 

 nitrogen as the second limiting element. 



In considering the data given in Tables 37, 38, and 39, it should 

 be kept in mind that each table gives results that are complete 

 and entirely independent. Thus, by using three different tracts 



