60 BULLETIN 690, U. S. DEPARTMENT OF AGRICULTURE. 



1907.^ These experiments had several objects in view but were 

 conducted chiefly to test the relative fertilizer value of the soluble 

 and the relatively insoluble phosphates on corn, wheat, and hay. 



The field used is said to be fairly level, well drained, and quite 

 uniform throughout. The soil was moderately stiff clay. The his- 

 tory of the cropping of this field before the experiment was under- 

 taken is as follows: 



In 1888 the land grew a poor crop of weeds and grass which was 

 plowed down. The land was then sown to wheat which was har- 

 vested in 1889; in 1890 and 1891 the field was in grass, and in 1892 

 corn was planted. The land was fallowed in 1893, but in 1894 it 

 was again planted to wheat in which both timothy and clover were 

 sown. 



In 1895 2 the field was divided into 22 plots of one-tenth acre each 

 and planted to corn, crimson clover being sown subsequently in the 

 corn on plots 1 to 12, and rye on plots 18 to 22. These latter crops 

 were plowed under the following spring. In 1896, 1897, and 1898^ 

 corn was again grown under the same conditions. In 1899 a crop 

 of wheat was harvested followed by hay in 1900 and 1901. In 1902 

 and 1903 corn was again grown followed by wheat in 1904 and hay 

 in 1905. ' 



The various phosphates were applied in such quantities as to fur- 

 nish equal' amounts of phosphoric acid to the soil. It appears that 

 the phosphate applications were made every year except in 1899, 

 1900, 1901, and 1905 when wheat and hay were the crops grown. 



There were four check (no phosphate) plots employed in this 

 experiment, on two of which a green crop (rye or clover) was turned 

 under subsequent to the growing of corn. In the tables given below 

 only the average of these four plots is reported. Three plots each 

 were treated with the following phosphates in quantities supplying 

 150 pounds of PgOg per acre, raw bone meal, basic slag, ground 

 South Carolina raw rock and Florida soft phosphate. Two each 

 of these plots had a green crop turned under in six out of the 12 

 years of the experiment, in order to study the effect of decaying 

 organic matter on the availability of these relativel}^ insoluble phos- 

 phates. In the following tables the average of the three plots is 

 taken in each instance, although in some cases the organic matter 

 present apparently increased the effectiveness of the phosphate treat- 

 ment. 



2Md. Agr. Expt. Sta., Bui. No. 114 (1907). 



3Md. Agr. Expt. Sta., 8th Ann. Kept, p. 226 (1895). 



■The corn crop in 1898 was a failure. 



