914 EXPERIMENT STATION RECORD. 



experiments which indicate that nitrogen is easily absorbed by plants 

 in this form. Breal 1 has shown that nitrogen is also taken up by 

 plants in the form of hu mates of lime or potash. 



Hellriegel has shown in experiments with barley fertilized with vari- 

 able amounts of nitrates that the amount of water transpired by the 

 plant per gram of dry matter increases as the amount of nitrate applied 

 decreases. Barley, which received the most favorable amount of 

 nitrates, evaporated 263 gm. of water per gram of dry matter produced. 

 Tbe plants which received no nitrates and which made a sickly growth 

 evaporated from 700 to 800 gm. of water per gram of dry matter. 

 Normal, vigorous plants obviously evaporate more water than sickly 

 ones, but if we calculate the ratio of the quantity of water transpired 

 to the weight of dry matter produced we find that the proportion is 

 greater in the sickly than in the vigorous plants. This fact may be 

 useful in determining the efficacy of a fertilizer. 



By pursuing this method of investigation the author found that the 

 Graminea? and Leguminosse do not take up and utilize jfiant food in the 

 same manner. The Gramineae are especially benefited by chemical fer- 

 tilizers, particularly nitrates, while they do not utilize humus sub- 

 stances to very great advantage. On the other hand, Leguminosre are 

 more benefited by the humates than by nitrates or ammonia salts. 



Eye grass and clover were planted in large pots, each of which con- 

 tained 50 kg. of soil exhausted by continuous cropping. Equal amounts 

 of phosphoric acid, potash, and nitrogen were applied. In one case 

 the nitrogen was applied in the form of nitrates, in the other in the form 

 of hamate. A black extract from manure which contained a mixture 

 of humate of potash and humate of ammonia was also used. At the 

 end of the experiment it was found that the rye grass which had received 

 no manure had transpired CS2 gm. of water per gram of dry matter, 

 that which had received humates 435 and 409 gm., and that which had 

 received only chemical fertilizer 233 gm. The results were quite differ- 

 ent with clover. In this case the transpiration was: Without manure 

 454 gm., with chemical fertilizers 398 gm., and with humates 272 and 

 265 gm. These results confirm the conclusions of Breal, Snyder, and 

 Lawes and Gilbert. The latter have shown at Kothamsted that it was 

 impossible to grow clover continuously on the same land unless the soil 

 was abundantly supplied with organic manures. 



To summarize, then, nitrogen is taken up by plants in the form of 

 nitrates, ammonium salts, and alkaline humates. The Leguminosa' 

 can utilize free nitrogen only when it has been brought into combina- 

 tion by the action of the organisms of the root tubercles. It has fre- 

 quently been claimed that other plants besides the Leguminosic are 

 capable of absorbing free nitrogen, but it has been shown that this 

 absorption does not take place without the intervention of the organ- 

 isms which fix nitrogen. 



1 Aim. Agron., 20 (1894), p. 353 (E. S. R., 6, p. 284). 



