EXPERIMENTS WITH NITROGEN FERTILIZERS 15 



Some minor changes were made in the appHcations of fertilizers and lime in 

 1919. Up to this time, dissolved boneblack had been used continuously as the 

 phosphoric acid fertilizer and dried blood as the organic nitrogen fertilizer. 

 Both were no longer in common use. Acid phosphate, or plain superphosphate 

 as dissolved rock phosphate was called, was now the standard source of phosphoric 

 acid and was substituted for the boneblack. Dried blood was now in demand as 

 a food for calves and pigs. A new synthetic nitrogen fertilizer, cyanamid, was 

 introduced on Plot 3; and a standard organic substance, ground fish, was sub- 

 stituted on Plot 10. The application of fish carried with the nitrogen a small addi- 

 tion of phosphoric acid, which was ignored because there had always appeared 

 to be a surplus of that plant food and the phosphoric acid in fish was less soluble 

 than that yielded by superphosphate. 



Lime had been liberally applied on the east half of everj^ plot, and with most 

 crops there was a sharp demarcation between the unlimed and limed areas. But 

 a comparison of yield between the two halves was unfair because the east side of 

 the field was definitely, though slightly, moister than the west half. In 1919, 

 one ton per acre of ground limestone was applied to the north half of each plot 

 except Plot 6 and Plot 8. These were duplicate plots with ammonium sulfate 

 and it was deemed to be a better comparison of the value of lime as an accom- 

 paniment to ammonium sulfate with Plot 8 limed throughout and Plot 6 left 

 without any addition. 



The change in sources of phosphoric acid and organic nitrogen did not appear 

 to alter the relative standing of the different fertilizers. 



The proportions of weights of ears to weights of stover in the different corn 

 crops indicate that the addition of nitrogen promoted the development of ears. 



In 1883, the first year of these experiments, Longfellow flint corn was grown 

 without fertilizer; the yields were fairly uniform on all the plots and the ratio of 

 ears to stover averaged 1 : 1.8. 



In 1889, the first year of the comparison of nitrogen fertilizers. Plots 7 and 9 

 without nitrogen bore small quantities of ears, while the weights of stover were 

 equal to those on the nitrogen plots. The proportions of ears to stover on 7 and 

 9 were respectively 1 : 12 and 1 : 7, while the crops on the nitrogen plots had an 

 average ratio of 1 : 2.3. Plot 4, also without nitrogen, differed somewhat from 

 Plots 7 and 9. Its crop was somewhat heavier in weight of ears, but much less 

 in stover, and the ratio was 1 : 3. 



Plot 4 had been without fertilizer of any kind until 1889, while Plot 7 had 

 received phosphoric acid and potash, and Plot 9 had received potash. Plot 4 

 had borne about one-third as much fodder as had been produced on 7 and 9, 

 due to the lack of available potash. In 1889, the latter plots had exhausted 

 their soil nitrogen more than Plot 4, while accumulating available potash. The 

 failure to produce ears when nitrogen is lacking was noticeable. The need of 

 potash to produce growth was also apparent. 



Subsequent corn crops corroborated the relation of nitrogen to ear produc- 

 tion. Rustler dent com was grown in 1906, 1911, and 1912. The crop of 1911 

 was grown upon a clover sod, which supplied all the nitrogen that the different 

 plots needed, and the proportions of ears to stover were nearly uniform around 

 1 : 0.9. The following year, 1912, the ratios separated a little and averaged 

 1 : 0.85 with the nitrogen plots and 1 : 1.05 for the plots without nitrogen. The 

 crop of 1906 had wider differences between the two groups of plots, with an 

 average ratio 1 : 1.1 for the nitrogen plots and 1 : 1.7 for the other group. 



