98 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
fertility of the various plots, the indications are that the average 
natural productivity of the check plots and those afterwards re- 
ceiving only a mixture of potash and nitrogen, was greater than that 
of the plots on which phosphates were applied. It will also be seen 
that the average yield of the plots afterwards treated with acidulated 
phosphate was less than the average of any of the other plots. € 
A regular four-year rotation of wheat, grass, corn, and oats was 
begun in 1884. The fertilizers were applied only to the wheat and 
corn crops, being sown broadcast after the field was plowed, and 
subsequently harrowed in. Muriate of potash and ammonium sul- 
phate were applied to each plot (except the checks) at a rate sup- 
plying 100 pounds of potash (K,O) and 47 pounds of nitrogen, respec- 
tively. The phosphates were applied at a rate supplying 32 pounds 
of phosphoric acid (P,O,). During the entire period of the experi- 
ment fertilizers have been applied six times. 
The average results obtained from duplicate plots are 5 poe in 
Table LIX. 
TABLE LIX.—Average yields of various crops grown in four-year rotation on the 
same field for a period of 12 years (1884-1895). 
Average yield (three years) per acre. 
Plot letter. Fertilizer. tion per 
acre.! | Wheat, | Grass, | Corn, 
grain. hay. ears. 
——_———_ JE ————— ——_ | | — __—____ 
Pounds.| Bushels.| Pounds.| Bushels.| Bushels. 
28. 23 3, 167 48. 86 43. 42 
AvandiG 4 esse. ht Dissolved bone black.......... 
Muriate of potash............. 
Ammonium sulphate.......... 240 
IBrandvie so cease eoceeee Reverted phosphate........... 200 
Muriate of potash -. 2. .2....... 200 
Ammonium sulphate......... 240 
Cran Olea ese e ee ck oe Finely ground bone........... 150 
Murnatelonpobashes-esesesceee 200 
Ammonium sulphate......... 240 
150 
200 
240 
200 
240 
SS 
29.89] 3,300] 49.60] 47.10 
31.58] 3,365] 51.96 49.39 
LOCK: BAe ok > eee IY res 
Muriate of potash............. 
Ammonium sulphate.......... 
Rand aK ee seecien eee Muriate of potash............. 
Ammonium sulphate.......... 30. 57 2,492 40. 68 45. 54 
YANG byes scone cobeeee INOenilizente ee eee eee ees Se ee. 22. 52 2,048 33. 07 38. 81 
31. 56 3, 133 47. 64 48. 24 
1 Applications made every other year. 
Considering now the average yield of each crop from the variously 
treated plots during the 12 years in which the fertilizer effects 
were studied, we find that larger yields of wheat (grain) were ob- 
tained on the less soluble than on the readily soluble phosphate plots, 
and that the plots treated with raw rock phosphate compared favor- 
ably with those receiving any other form of phosphoric acid, even 
when the apparent natural fertility of the various plots (as deter- 
mined by the crop of oats grown in 1883) is taken into consideration. 
In the case of hay (grown in 1885, 1889, and 1893) the produc- 
tion on the plots treated with other forms of phosphoric acid showed 
