70 



BULLETIN 699, V. S. DEPARTMENT OF AGEICULTURE. 



and above the check plots) obtained from plots treated with the 

 different types of phosphates up to the close of 1914, 



In reporting these results Brooks discarded the yields obtained 

 during the first two years of the experiment on the assumption that 

 the difference in the natural fertility of the plots would be less 

 strongly marked after two years of fertilization. It might be said, 

 however, that if the same plan had been followed in the earlier 

 experiment where equal money values of the various phosphates were 

 applied the average results would have been even more favorable to 

 the less soluble phosphates than reported. 



In comparing the crop yields in this later experiment each plot 

 was compared with the check plots between which it lay and these 

 checks were given a weight inversely proportional to their distance 

 from the plot for which they served as a basis of comparison. 



The validity of such a method of comparison is based on the as- 

 sumption that the variations in the fertility of a field are fairly 

 regular. Other investigators consider that a comparison of the 

 average yield of all check plots with each treatment is a much fairer 

 basis on which to compute differences in fertilizer values. 



Table 'KXKIX.— Average increase per acre in corps prodticed on plots treated 

 with different classes of phosphates (1899-1914). 



Fertilizer. 



Corn, 3 

 years, 1899, 

 1913, 1911. 



Hay, 2 years, 1906, 1907. 



Onions, 2 



years, 1901, 



1902. 



Cabbage, 

 2 years, 



1903, 



1908. 





Grain. 



Stover. 



Hay. 



Rowen. 



Total. 



Sound. 



Seal- 

 lions. 



Natural mineral phosphates 



Basic slag and bone meals 



Dissolved phosphates 



Bush. 



-1.06 

 8.03 

 9.96 



Lbs. 

 318. 87 

 905. 50 

 651. 11 



Lbs. 

 398.30 

 615. 55 

 753. 33 



Lbs. 

 -131.00 

 97.33 

 350. 67 



Lbs. 

 267. 30 

 712. 88 

 1,104.00 



Bush. 

 -30. 60 

 143. 60 

 136. 73 



Bush. 



10.76 



-19.23 



-12. 56 



Lbs. 

 9,817.50 

 21,026.(0 

 18, 758. 60 







Fertilizer. 



Oat hay, 

 1 year, 

 1900. 



Hun- 

 garian 



hay, 

 1 year, 



1900. 



Ensilage 



corn, 1 



j^ear, 



1904. 



Soy beans, 1 

 year, 1910. 



Potatoes, 1 

 year, 1910. 



Oat and 

 alfalfa 

 hay, 1 

 year, 

 1911. 



Alfalfa 

 hay, 1 



Grain. 



Straw. 



Market- 

 able. 



Total. 



year, 

 1911. 



Natural mineral 

 phosphates 



Basic slag and bone 

 meals . - 



Lbs. 

 231.70 



1,324.40 



1, 520. 00 



Lbs. 

 166. 70 



-222. 23 



-253. 30 



Lbs. 

 -1,638.70 



7,608.90 



7,361.30 



Bush. 

 0.77 



4.09 



3.87 



Lbs. 

 290. 56 



794. 67 



776.00 



Bush. 

 -10.70 



16.40 



26.90 



Bush. 

 -8.30 



18.90 



29.50 



Lbs. 

 80. 00 



1,026.67 



1,560.00 



Lbs. 

 91.70 



244. 40 



Dissolved phos- 

 phates 



73.30 







It will be seen by dividing the phosphates into classes and taking 

 the average yield of each class, as Brooks has done in his summarj'-, 

 the soluble phosphate plots on the whole surpassed all the other 

 phosphates. Next in order came the so-called available phosphates, 

 consisting of raw bone, steamed bone, and basic slag, and finally 



