EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 39 
limestone was applied to plots 1 to 15 at the rate of 1,300 pounds per 
acre in 1906 and again in 19138 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 four years.? 
The average results of 11 years with four crops is given in 
Table XV. 
TABLE XV.—Average resulis of 11 Years’ work on four fields at Rockford, 
Iil.—Four-year rotation, consisting of corn, corn, oats, and clover. 
Average yield per acre. 
Treatment. g 
Corn, Oats, Clover, wee Timothy, 
11 years. 11 years. | 7 years. 3 years lyear 
Bushels. | Bushels. Tons. | Bushels. Tons. 
Iban’ BS 9 Wik et ge S Nk A oe Ra ah SE a A ee oe RO 54. 64 57.98 1.83 9.65 1.65 
EVOSICUI OS tITMOt ern weeny Maninnt Spel ieee cera 60.75 61.18 11.22 10. 67 1. 66 
Manmretlinie: tetera ey iy it eT ee Re eee 68. 84 60. 76 1.96 14. 89 1.65 
@overcropemanure, lime... 2..c06cslesc 01 scdeccleee 66. 65 59. 50 2.04 14. 66 1.59 
nie eee | Se empha FO PEs Bays: 58. 83 54. 90 1.91 10. 90 1.59 
MIME TMHOSPHAtOLOCK joe fcc hc cmc sce dees ie njiee nace onc 61.94 61.59 2.14 11.94 1.44 
Residues, lime, phosphate rock..............-------- 66. 44 59. 85 11.96 14.19 1.52 
Manure, lime, phosphate rock................ss+-+-- viata 62. 22 2. 22 18. 64 1.47 
Cover crop, manure, lime, phosphate rock.........-- 69. 69 61. 86 2. 26 19. 69 1.45 
Lime HSS SA GEOE OS SE Cee SE nei TN re ar en 57. 03 57.18 1.84 16.78 1.47 
Lime, phosphate rock, potash -....-....22.2.5.00222- 69. 73 60. 86 2.36 13. 02 Ley) 
_ Residues, lime, potash, phosphate rock.............. 69. 82 61. 72 12.00 13. 48 153 
Manure, lime, potash, phosphate rock...........---- (Os 59. 73 2.38 18. 44 1.43 
Cover crop, manure, lime, potash, phosphate rock... 71.80 62. 89 2.45 22. 30 1.41 
Mee SE ee Fae: eee are ar Bs 8 Ee Ue Be Sa 60. 19 56. 30 1.85 TEAS 1.62 
HEUOSICU CSB eae ener ere aie bans c cherie a ie wider ace 64. 40 60. 16 11.94 13.10 1.65 
Residues: phosphate rocks 222.2 52222. S228 sk 67.30 61. 70 11.98 12.63 1.62 
Residues, phosphate rock, potash..-...-...........-- 69. 51 63. 78 11.94 12.01 1.45 
Residues, lime, nitrogen, potash, phosphate rock.... 73. 25 68. 82 12.08 13. 16 2.46 
INONG: hese Ssacs BS BS GOS Sao R EE aS Reese a tae Beene 54. 72 58. 83 1.89 10. 34 1.40 
1A verage 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 series in like quantity 
2]ll. Expt. Sta., Soil Rept. No. 12, pp. 18-20 (1916). 
