36 



BUIXEOTriSr 699, U. S. DEPARTMENT OF AGEICULTTJBE. 



one of the four tracts. The average results obtained in nine years 

 for each crop on the tiled and untiled land are given in Table XII, 

 which is compiled from four tables given in Soil Report No. 8 of the 

 Illinois station. 



Table XII.^ — Average yields of corn, soy leans, wheat, and clover obtained on 

 four series of plots at Fairfield, III., in an experiment conducted for nine 

 years (1905-1913, i/nclusive). 





Average yield per acre. 



Treatment. 



Com, 

 8 years. 



Soy 

 beans, 

 6 years. 



Wheat, 

 7 years. 



Clover, 

 6 years. 



Oats, 

 lyear. 



Cowpeas, 



4 years. 





Bushels. 

 36.58 

 28.90 



35.54 

 46.91 



Bushels. 

 8.23 

 6.28 



6.02 

 9.09 



Bushels. 

 13.79 

 4.17 



5.21 

 18.03 



Bushels. 



0.67 



.45 



Tom. 



0.57 



1.61 



Bushels. 

 35.8 

 27.9 



32.5 

 38.7 



Bushels. 

 6.08 





5.10 





5.68 





7.53 







Organic manures, lime, phosphate rock. . . 



41.86 

 32.21 



8.67 

 6.16 



15.90 

 4.69 



Bushels. 



0.82 



.48 



37.2 

 30.2 



6.80 

 5.40 







Increase due to lime and phosphate 

 rock 



9.65 



2.51 



11.21 



.34 



7.0 



1.75 







The authors state that the first four years of this experiment should 

 be regarded as preliminary, partly because of the impossibilitj^ of 

 obtaining full benefit from such treatments during the first rotation 

 period, and also because the system of returning manure and crop 

 residues in proportion to the yields produced was not begun until the 

 first rotation was completed. But even taking the average yields of 

 the various crops during both the first and second rotations, it will 

 be seen that the plots treated with large amounts of raw-rock phos- 

 phate in connection with lime and organic manures produced consid- 

 erably larger crops than those receiving no phosphate. The effect 

 of the phosphate, however, was apparently more marked during the 

 second rotation period, as can be seen by referring to the more de- 

 tailed figures given in Soil Report No. 8 of the Illinois station. 



Two experiments with raw-rock phosphate conducted over a period 

 of five years were reported by Hopkins ' in 1915. 



One field at Ewing, Franklin County, consists of a gray silt loam 

 on compact clay (prairie soil), the other at Raleigh, Saline County, 

 is situated on a yellow-gray silt loam of the common upland timber 

 type. The previous history of the fields is not given, however, nor are 

 any data presented showing the uniformity of the fields or the size 

 of the plots into which they were divided. Each field contained 4 

 series of 10 plots each, and since a four-year rotation of wheat, a 

 legume, oats, and corn was followed, each crop was grown every year. 

 Both live-stock and grain systems of farming were practiced on each 

 farm. 



» ni. Agr. Expt. Sta., Circular No 181 (1915), 



