EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 



109 



VIRGINIA. 



In an article entitled "A Study of the Effect of Fertilizers on the 

 Soluble Plant Food in the Soil, and on the Crop Yield," Ellett and 

 Hill,^ showed the impracticability of accurately correlating the solu- 

 bility of phosphates in a certain conventional solvent with their avail- 

 ability to crops under soil conditions. The analytical work connected 

 with the problem was checked against field results with corn ex- 

 tending over a period of five years. 



The soil of the field used in this experiment was derived from the 

 Shenandoah limestone, and consisted of a light gray (Hagerstown) 

 loam, ranging from 6 to 10 inches in depth and underlain by a red- 

 dish yellow clay subsoil. " The cropping history of this particular 

 soil is not definitely known, but it has probably been under cultiva- 

 tion for not less than 75 years." The total phosphoric acid content 

 (0.113 per cent) was ample, though only 0.07 per cent was shown by 

 the ordinary hydrochloric acid digestion method of analysis. 



The annual application per acre of the various fertilizers and the 

 yields of corn (grain) *obtained are shown in Table LXV. Since 

 none of the other phosphates was used in connection with carriers of 

 nitrogen and potash, a comparison between them and acid phosphate 

 is only possible where the latter was used alone. The results obtained 

 on plots treated with mixtures of acid phosphate, nitrogen, and pot- 

 ash are, therefore, omitted in the table. 



Table LXV. — Yields per acre of corn ohtaAned on plots receiving various forms 

 of phosphoric acid (1907-1911). 



Plot 

 num- 

 ber. 



Fertilizer. 



Applica- 

 tion per 

 acre. 



1907 



1908 



1909 



1910 



1911 



Average 



yield 



for five 



years. 



1 





Pounds. 

 600.0 

 200.0 

 99.6 

 99.6 

 192.0 

 192.0 

 400.0 



Bushels. 

 46.61 

 41.79 

 46.61 

 43.93 

 41.79 

 37.50 

 39.11 

 43.93 

 40.71 

 42.86 

 42.86 

 43.93 

 44.46 

 42.86 

 40.71 

 40.18 



Bushels. 

 45.00 

 48.21 

 46.61 

 53.35 

 44.46 

 41.79 

 38.57 

 40.18 

 51.43 

 45.00 

 46.61 

 53.57 

 47.14 

 53.57 

 62.14 

 31.07 



Bushels. 

 42.95 

 41.79 

 39.64 

 39.11 

 39.11 

 30.00 

 32.68 

 36.96 

 39.64 

 36.43 

 43.39 

 52.50 

 39.64 

 46.08 

 38.03 

 36.96 



Bushels. 

 37.50 

 30.53 

 25.71 

 27.32 

 19.28 

 21.42 

 14.82 

 24.64 

 24.10 

 24.10 

 28.92 

 39.65 

 30.00 

 30.00 

 15.00 

 17.85 



Bushels. 

 30.53 

 34.82 

 36.43 

 34.28 

 31.60 

 31.07 

 21.43 

 19.29 

 24.10 

 30.00 

 37.50 

 47.68 

 34.82 

 35.36 

 37.50 

 33.21 



Bushels. 

 40.51 



2 



do ............. ..... 



39 43 



3 



Floats 



39 00 



4 



do 



39.59 



5 



Thomas slag 



35.24 



6 



do 



32.35 



7 



A cid phosphate 



29.32 



11 



Check 



33.00 



12 

 13 

 14 



do 



do 



.. do 





35.99 

 35.67 

 39.85 



18 



Lime 



1,200.0 



47.46 



19 



Check 



39.21 



20 

 23 

 24 



do 



do 



do 





41.57 

 44.59 

 35.35 











I Not included in average. 



The results obtained in this experiment are very confusing. If the 

 difference in the yields of the check plots be considered for any 



» Va. Agr. Expt. Ste. (Blacksburg). Ann. Kept for 1911-12, pp. 116-132 (1913). 



