!"''> Food for Pi.ants. 



best, or iiiosl crt'cctive. It will he reim'iiil)eied thai this 

 cylinder recoivos cow iiiamirc at Uio rate of 16 tons per 

 acre annually, the cost of whicli would be much in excess 

 of the cost of 320 ])ounds of nitrate of soda or its 

 ('(luivalent in amnioninm sulfate or dried blood, and 

 thei-efore the lar^'cr yield does not necessarily mean an 

 efficient use of the applied nitrogen. As a matter of 

 fact, the \vork shows this to be the least efficient of the 

 four forms. 



Percentage of Nitrogen Recovered in the Crops. 



Reference has already been made to the method of cal- 

 culating the percentage of nitrogen that is recovered in 

 the crop. The recoveries for the four dilTerent treat- 

 ments covering the 20 years are shown in table 2. The 

 averages for the period are as follows : 



4B 32.69 per cent, (manure) 



8B 62.42 per cent. (Nitrate of Soda) 



17B 47.48 per cent, (ammonium sulfate) 



18B 48.69 per cent, (dried blood) 



This means that of 100' pounds of nitrogen applied in 

 the four different forms approximately one-third, three - 

 fifths, one-half, and two-fifths, respectively, are recov- 

 ered or won back in the crop. As has already been men- 

 tioned, these figures agree quite closely with results 

 reported from European countries, and they also confirm 

 earlier work carried out at this Station. 



But even so, they are not satisfying figures. We at 

 once ask why there is this enormous loss of nitrogen and 

 especially why the loss is so much greater w^ith the 

 organic materials than with the nitrate of soda and am- 

 monium sulfate. If the loss is to be attributed to the 

 leaching out of the materials, then it would seem that 

 the figures should be reversed. Unquestionably, a cer- 

 tain amount of loss takes place in this way, but this can- 

 not explain the loss of over two-thirds from the manure 

 against a little more than one-third from nitrate. 



It is well known that organic materials must undergo 

 certain transformations in the soil before the nitrogen 



