USE OF PHOSPHORUS IN DIFFERENT FORMS 283 



"It appears reasonable to believe that on soils of the character of this field 

 the farmer may safely depend for a considerable portion at least of the phos- 

 phorus needed by his crops upon the cheaper natural phosphates, such as finely 

 ground South Carolina rock and finely ground bone, while phosphatic slag also 

 promises to give a most useful fertilizer upon soil of this character." 



This entire field, including the no-phosphate plot, has received 

 52 pounds of nitrogen and 126 pounds of potassium per acre per 

 annum for the ten years. The phosphate plots have each received 

 42 pounds of phosphorus per acre each year; but no provision was 

 made for maintaining organic matter in the soil. It should also 

 be kept in mind that the raw phosphates that gave poor results 

 may not have been ground to a sufficient degree of fineness. 



The Illinois Experiment Station is conducting much more ex- 

 tensive experiments than any other state with the use of fine- 

 ground natural rock phosphate, but these investigations were begun 

 too recently to furnish information from which such final conclu- 

 sions can be drawn as from the Ohio work, for example. 



In Table 50 are reported results obtained from the University 

 of Illinois soil experiment field near Galesburg, Knox County, on 

 the ordinary brown silt loam prairie soil of the Upper Illinoisan 

 glaciation, which, in 1903, contained in 2 million pounds of the 

 surface soil 5020 pounds of nitrogen, 1160 pounds of total phos- 

 phorus, and 31,700 pounds of potassium. 



A six-year rotation is under way on this field, including corn for 

 two years, oats the third year, and wheat the fourth, followed by 

 two years of clover and timothy. (After the first six years the 

 rotation will be corn, corn, oats, clover, wheat, clover.) There are 

 three independent series of plots, so that every year corn is grow- 

 ing on one series, oats or wheat on another series, and clover and 

 timothy on the other. 



The land was timothy sod at the beginning, and Series 300 was 

 not broken during the first two years, \ ton of phosphate per acre 

 having been applied at the beginning as a top dressing, which, as 

 was expected, produced practically no effect. A ton of phosphate 

 per acre applied in the beginning to Series 200 produced no effect 

 on the oats seeded on timothy sod in 1904, and but little effect 

 on the wheat which followed in 1905. The regular plan is to apply 

 i^ tons of raw rock phosphate per acre to the clover and timothy 



