FERTILIZERS. 



133 



"Four pots were devoted to each of the 6 fertilizers. To the soil in 1 of these 4 

 pots "vvas added 1 decigram of organic nitrogen, supplied by the fertilizer under 

 experiment. The second pot received 2 decigrams, the third pot 4 decigranjs, and 

 the fourth pot 8 decigrams of organic nitrogen." 



Water was carefully poured ou the surface of each pot uutil the total 

 weight was 5,800 gin. In every case 10 cc. of extract of garden soil 

 was added, and a dwarf variety of corn was planted, 3 stalks of which 

 were allowed to grow in eiich pot. The pots were watered from time 

 to time with water from the city service pipes filtered through a Pas- 

 teur-Chamberland filter, the water content being brought to 4() per cent 

 and uot allowed to siuk below 30 per cent. It was found that if the 

 water content sank as low as 20 per cent the plant suffered. 



The plants were "small and im])crfectly developed, and produced no 

 ears on account of the limited supply of nitrogen," but entirely healthy 

 and thrifty in appearance. Wlien they had finished growing the crop 

 in each pot was harvested separately, weighed, and the percentage of 

 nitrogen deternnned. 



The following table shows the comparative availability of the nitro- 

 gen of the 6 fertilizers used — shown by pepsin digestion, putrefaction, 

 gain in nitrogen in crop, and increase in croj), all expressed in per cent 

 of availability of the nitrogen in the best fertilizer: 



Comparison of peptic, putrefactive, and cnltnre teiita of availability of nitrotjen in differ- 

 ent fertilizers. 



Relative nitrogen-solubility by pepsin 



Relative nitrogensdlubility by putrefaction 



Relative cro))-])ro(liuinii. ])()\ver 



Relative gain of nitrogen 



F. 



"The nitrogen of sample E shows throughout the greatest peptic and putrefactive 

 sohibility as well as greatest croi)-produciug capacity, and with one exceiiticm (C) 

 has given the most nitrogen to the crops. Sample I> has yielded the least S()lul)le 

 nitrogen to i>epsiu and under putrefaction, but D, in the culture test, is least eft'ective 

 as a fertilizer. Samples A, C, and E, which vary so widely in the peptic and putre- 

 factive solubility of their nitrogen, manifest very little ditference in their average 

 crop-producing powers as measured by either the crop increase or gain of nitrogen 

 by the crops. 



"It is evident that the tedious vegetation cultures are the only true test of the 

 availability of organic nitrogen, while the pepsin digestion may give useful indica- 

 tions but can not be depended ou for decisive results. 



"If opportunity otters it is purposed to continue investigations in these or similar 

 directions." 



Guide to the use of fertilizers in Algeria, F. Dep.kay (Paris: A. Challamel, 

 ISO 4, pp. 7S.) 



How can the farmer conserve and increase his supply of nitrogen? J. Konig 

 (Berlin: Paul Parey, third edition, pp. 1S4). Revised in collaboration with E. Hasel- 

 hott'. 



The utilization of the nitrogen of stable manure and of green manures, J. KOhn 

 (Deut. landw. Presse, 2L (1S94), ^Yos. 3o, 34, 40,51). 



