l82 



Journal of Agricultural Research 



Vol. XIII, No. 3 



Table VII. — Periodic changes in nitric nitrogen {Series I) 

 [Results expressed as pounds of nitric nitrogen per 2,000,000 pounds of soil] 



Material. 



Control soil 



Legume mixtures: 



Soybean 



Canada field pea 



Sweet clover 



Alfalfa 



Red clover 



Hairy vetch 



Subaverage 



Nonlegume mixtures: 



Wheat 



Rape 



Oats 



Com 



Timothy 



Rye 



Redtop 



Sorrel 



Subaverage 



Bamyard-manure mixture 

 Poultry-manure mixture « 



Grand average 



Second and 



third 



months. 



14. 28 



24.84 

 64.82 



74-50 

 84.60 



30-36 

 19.36 



49-75 



61. 64 

 69. 02 

 60. 22 

 55-08 



2.86 

 29. 80 



4-32 

 13.28 



37.02 



2. 76 

 (?) 



39-83 



Fourth and 



fifth 



months. 



O. 06 



65.40 

 II. 10 

 18.98 

 20.34 

 1 50. 06 

 46. 22 



52.02 



9. 20 

 86.76 



36-74 

 17. 00 

 21. 80 

 14. 72 

 30.96 

 33-40 



31-32 



25.72 



68.68 



39-23 



Sixth and 

 seventh 

 months. 



16. 62 



•74 



•12. 02 



54-46 



29.58 



O. CO 



23.70 



16.08 



91.30 

 -1.84 



IS- 50 

 38.20 

 25. 22 

 21. 62 



10. 72 



11. 18 



26. 49 



5-50 

 -30. 68 



20. 90 



Eighth and 



ninth 



months. 



5.20 



6.08 

 24. 98 

 -12. 42 



8.46 

 62. 00 

 II. 52 



16.77 



-31.04 



— 7. 16 

 19. 00 



7.68 

 II. 64 



6.48 

 14.84 

 20.88 



5-29 



22.58 

 42. 96 



11.03 



a Omitted from grand average. 



In the second place, even under the assumption according to which 

 the nitrification would most largely increase the limestone requirement — 

 namely, that the nitrates were formed from the previous stock of am- 

 monia, and that the ammonification was entirely completed prior to the 

 period in question — the quantities of nitric nitrogen found are alto- 

 gether insufficient to account for the large development of the limestone 

 requirement. Thus, if the 31.17 pounds of nitric nitrogen found at the 

 end of the fourth week are assumed to have formed during the preceding 

 14 days, and it is further assumed that ammonification was arrested 

 during that time, the corresponding increase of the average limestone 

 requirement would be only 222.5 pounds, as compared with the observed 

 increase of 1,261 pounds; and, in this way, the 39.23 pounds increase 

 of nitric nitrogen during the fourth and fifth months could account for 

 no more than 280 pounds of the 1,596 pounds increase in limestone 

 requirement observed for that period. 



The further fact that the second and third month witnessed a decrease 

 in the limestone requirement and that this condition prevailed also, in the 

 average case, during the eighth and ninth months, whereas nitric nitrogen 



