EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 77 



Not only was no comparison made between raw rock phosphate 

 and the acidulated phosphates in this experiment, but no strict com- 

 I arisen can be made between the plots treated with raw rock and those 

 receiving bone meal, as in every case the two forms of phosphoric 

 acid were used in conjunction with different fertilizers. The plots 

 (both drained and un drained) which were treated with raw rock, 

 manure, and a legume, however, showed substantial increases in yield 

 over those receiving only manure and a legume (except the drained 

 com plot in 1908, and the undrained oat plot in 1909). 



iM tiler, Hutchison, and Hudelson^ described four other experi- 

 ments in which an attempt was made to study the relative fertilizer 

 merits of raw rock phosphate and steamed bone meal in four-year 

 rotations. The experiments were conducted on four series of plots 

 so that each crop was grown every year. The work was carried on at 

 the following places: Jasper County, near Carthage; on the High 

 Hill experiment field, Montgomery County; on the Hurdland ex- 

 periment field, Knox County; and on the Laclede experiment field, 

 Linn County. 



The Jasper County experiment ^ was conducted for a period of 

 only four years and is therefore not repeated in detail but the indi- 

 cations were that raw rock was quite effective when used in conjunc- 

 tion with manure, the average yield of these plots leading all others, 

 with the exception of the average yield of wheat on the plots treated 

 with lime, bone meal, and potash. In this experiment also there was 

 no comparison made between acid phosphate and the less soluble 

 forms of phosphoric acid. 



The experiment field at High Hill,^ Montgomery County, Mo., is 

 located " on a slight ridge which slopes considerably to the west 

 from the center of the field, with the east one-fourth sloping slightly 

 to the east. In neither case is the fall sufficient to cause the land to 

 wash badly." The field had been cropped to com and oats for about 

 twenty-five years, being in com about two-thirds of the time. The 

 soil is a gray silt loam grading into a dull gray silt below, which 

 becomes heavier with depth, and interferes somewhat with the under- 

 drainage. The soil is low in nitrogen, but fairly well supplied with 

 phosphoric acid and potash. The plots were one-fifth acre each, 

 and were laid out lengthwise across the slope. The experiment 

 which was begun in 1907 was continued to 1913 (seven years) in a 

 four-year rotation of corn, oats, wheat, and clover, but some of the 

 crops were apparently not weighed. During the last year of the 



1 Mo. Agr. Expt. Sta., Buls. Nos. 119, 126, 127, and 128. 

 »Mo. Agr. Expt. Sta., Bui. No. 119, pp. 3-17 (1914). 

 •Mo. Agr. Expt. Sta., Bui. No. 126, pp. 326-333 (1915). 



