EXPEETMEN-TAL WORK WITH EAW EOCK PHOSPHATE. 



39 



limestone was applied to plots 1 to 15 at the rate of 1,300 pounds per 

 acre in 1906 and again in 1913 to the same plots at the rate of 4 tons 

 per acre. Raw rock phosphate was applied to the plots indicated 

 at the rate of 1 ton per acre every four years and potash in the form 

 of potassium sulphate was applied at the rate of 400 pounds per acre 

 every ft)ur years.^ 



The average results of 11 years with four crops is given in 

 Table XV. 



Table XV. — Average results of 11 years' work on four fields at Rockford, 

 III. — Four-year rotation, consisting of corn, corn, oats, and clover. 



Treatment. 



Average yield per acre. 



Com, 

 11 .years. 



Oats, 

 11 years. 



Clover, 

 7 years. 



Soy 

 beans, 

 3 years. 



Timothy, 

 lyear. 



Lime 



Residues, lime 



Manure, lime 



Cover crop, manure, lim.e 



Lime 



Lime, phosphate rock 



Residues, lime, phosphate rock '. 



Manure, lime, phosphate rock 



Cover crop, manure, lime, phosphate rock 



Lime 



Liine, phosphate rock, potash 



Residues, lime, potash, phosphate rock 



Manure, lime, potash, phosphate rock 



Cover crop, manure, lime, potash, phosphate rock 



Lime 



Residues 



Residues, phosphate rock 



Residues, phosphate rock, potash 



Residues, lime, nitrogen, potash, phosphate rock . 

 None 



Bushels. 

 54.64 

 60.75 

 68.84 

 66. 65 

 58.83 

 61.94 

 66.44 

 71.71 

 69.69 

 57.03 

 69.73 

 69.82 

 71.75 

 71.40 

 60.19 

 64.40 

 67.30 

 69.51 

 73.25 

 54.72 



Bushels. 

 57.98 

 61.18 

 60.76 

 59.50 

 54.90 

 61.59 

 59.85 

 62.22 

 61.86 

 57.18 

 60.86 

 61.72 

 59.73 

 62.89 

 56.30 

 60.16 

 61.70 

 63.78 

 68.82 

 58.83 



Tons., 



1.83 



1L22 



1.96 



2.04 



1.91 



2.14 



11.95 



2.22 



2.26 



1.84 



2.36 



12.00 



2.38 



2.45 



1.85 



11.94 



11.98 



11.94 



12.08 



1.89 



Bushels. 

 9.65 

 10.67 

 14.89 

 14.66 

 10.90 

 11.94 

 14.19 

 18.64 

 19.69 

 16.78 

 13.02 

 13.48 

 18.44 

 22.30 

 11.13 

 13.10 

 12.63 

 12.01 

 13.16 

 10.34 



Tons. 

 1.65 

 1.66 

 1.65 

 1.59 

 1.59 

 1.44 

 1.52 

 1.47 

 1.45 

 1.47 

 1.57 

 1.53 

 1.43 

 1.41 

 1.62 

 1.65 

 1.62 

 1.45 

 2.46 

 1.40 



lAverage of three years only. 



Just as in the case of several other experiments the results as re- 

 ported here fail to show the cumulative effect of the phosphate treat- 

 ments; but even taking the average yield of each crop for the entire 

 period the plots on which raw rock phosphate was applied show on 

 the whole considerably better yields than those receiving similar 

 treatments, but no phosphate. By referring to the original tables in 

 Soil Report No. 12 of the Illinois station, which gives the results of 

 each year in detail, it will be seen that the plots receiving organic 

 manures and raw rock phosphate were on the whole considerably 

 more productive during the later than during the earlier years of the 

 experiment, indicating very strongly that the effectiveness of the raw 

 rock phosphate was increasing. 



The Mount Morris experiment field ^ is located in Ogle County on 

 a brown silt loam prairie soil. Only the results of four years on one 



1 At the beginning of the experiment, however, potassium sulphate was not applied to 

 each sei'ies in like quantity 



» lU. Expt. Sta., Sou Kept. No. 12, pp. 18-20 (1916). 



