33 



another series (4 pots) received .84 gram of nitrogen per pot (119 

 pounds of nitrogen, 1124 pounds of blood per acre); and a third 

 series (2 pots) received 1.26 grams of nitrogen per pot (178.5 pounds 

 of nitrogen, 1686 pounds of blood per acre). The series containing 

 .84 gram and 1 .26 grams of nitrogen was used as a check to indicate 

 whether the full action of the nitrogen was obtained when the mini- 

 mum quantity (.42 gram) was used. (The use of the increased 

 amounts of nitrogen was accompanied by increased yields, proving 

 that conditions were favorable for the full effect of the smaller amount 

 which constituted the nitrogen standard, (.42 gram). A series of 

 pots was included which contained .42 gram of nitrogen from un- 

 washed blood, and in addition 50 per cent more potash and phos- 

 phoric acid, in order to show that the nitrogen was the only limiting 

 factor. (The yields were not appreciably increased by this additional 

 application). It seemed advisable to include one series (2 pots) in 

 which the nitrogen was derived from nitrate of soda, using .42 gram 

 of nitrogen per pot, (59.5 pounds of nitrogen, 384 pounds of nitrate 

 of soda per acre). 



Each commercial fertilizer used was washed with distilled water 

 so as to remove all soluble nitrogen. The residue, dried at a low 

 temperature, was tested for its total nitrogen and a calculation made 

 to determine how much of each fertilizer residue was necessary to 

 furnish .42 and .85 gram of nitrogen. Each fertilizer residue was 

 tested b}^ the alkaline permanganate method for its nitrogen activity, 

 in order to furnish a comparison of the laboratory method with the 

 vegetation experiment, using material in each case produced under 

 the same conditions. In some cases only one series of pots was 

 used to which was added .42 gram of nitrogen, the other series to 

 which more nitrogen was to have been added was omitted on account 

 of an insufficient amount of fertilizer. 



Oats were selected as the crop to be grown. The 

 Crop. seed was planted January 25th, — 5 hills per pot, 7 



seeds per hill. These were thinned later so that on 

 February 16th 2 plants were allowed to each hill. Mr. R. L. Coffin 

 of the agricultural department of the station cared for the experiment 

 during its continuance. Water was Supplied both through sub- 

 irrigation and surface application, the amount being regulated by 

 weighing each pot. The following data are taken from condition re- 

 ports which were made from time to time: 

 March 1 — -Pots 52 and 53 somewhat behind the others in growth, 



indicating some unfavorable conditions. 

 March 24 — Oats in all the pots were stooled out. In a few cases the 



oats in the nitrogen pots showed less growth than did 



those in the no nitrogen series. On smaller and weaker 



plants a mildew appears. 



