98 



BULLETIN 699, U. S. DEPARTMENT OF AGEICULTTJRE. 



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, com, 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 (K2O) and 47 pounds of nitrogen, respec- 

 tively. The phosphates were applied at a rate supplying 32 pounds 

 of phosphoric acid (P2O5). During the entire period of the experi- 

 ment fertilizers have been applied six times. 



The average results obtained from duplicate plots are given in 

 Table LIX. 



Table LIX. — Average yields of various crops grown in four-year rotation on the 

 same field far a period of 12 years (1884-1895), 



i^Iot letter. 



A and G 



B and H 



Candl 



D and J 



E and K 



FandL 



Fertilizer. 



Dissolved bone black 



Muriate of potash 



Ammonium sulphate 



Reverted phosphate 



Muriate of potash 



Ammonium sulphate 



Finely ground bone 



Muriate of potash 



Ammonium sulphate 



Finely groimd South Carolina 



rock 



Muriate of potash 



Ammonium sulphate 



Muriate of potash 



Ammonium sulphate 



No fertilizer 



Applica- 

 tion per 

 acre.i 



Pounds. 

 200 

 200 

 240 

 200 

 200 

 240 

 150 

 200 

 240 



150 

 200 

 240 

 200 

 240 



Average yield (three years) per acre. 



Wheat, 

 grain. 



Bushels. 

 I 28.23 



\ 29.89 



31.58 



31.56 



30.57 

 22.52 



Grass, 

 hay. 



Pounds. 

 3,167 



3,300 



3,365 



3,133 



2,492 

 2,048 



Com, 

 ears. 



Busliels. 

 48.86 



49.60 



51.96 



47.64 



40.68 

 33.07 



Oats. 



Busliels. 

 43.42 



47.10 



49.39 



48.24 



45.54 

 38.81 



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 



