THE LOSS OF KITROGEiT. 103 



nitrogen applied, but not recovered in one crop, is 

 available for those which succeed. The more favorable 

 is the season for the growth of a croj:), the better 

 will the crop be able to avail itself of the stores 

 of manure furnished by the soil and atmosphere. At 

 Kothamsted, the season of 1881 was very favorable for 

 the growth of potatoes; I therefore select that year's 

 crop, not as indicating what might be the average loss of 

 nitrogen applied in manure, but to show how very 

 serious may be the loss, even under exceptionally favora- 

 ble conditions. The following table gives the number of 

 bushels of potatoes of fifty pounds each: 



TABLE. 



Bushels per Acre.' 



(1) Potash, soda, magnesia, superphosphate 265 



(2) The same as (1) with 400 lbs. salts of ammouia 481 



Gain by addition of ammonia 219 



It is quite evident that the mineral manures enabled 

 the potatoes to gather up a large amount of nitrogen; 

 and that further growth was only arrested for want of 

 more nitrogen, is evident by the much larger crop grown 

 when a manure containing that substance was used; this 

 fact is still further confirmed by the analyses of the pota- 

 toes grown by mineral manures alone, Avhich show a very 

 low percentage of nitrogen. Assuming that the ordi- 

 nary potatoes in a dry state contain one per cent, of 

 nitrogen, these potatoes contained one-sixth less than 

 that amount, and it is probable that under such condi- 

 tions no further growth was possible. 



We now come to the loss of nitrogen. The four hun- 

 dred pounds of sulphate and muriate of ammonia are 

 estimated to furnish about eighty-five pounds of nitro- 

 gen. Taking the potatoes grown by mineral manures 

 alone at twenty-six pounds, we find in those grown by 

 ammonia and minerals sixty-six pounds, or an increase 

 of forty pounds; but as we supplied eighty-five pounds 



