No. 6. DEPARTMENT OF AGRICULTURE. 353 



nitrates, is diminished by vegetation; hence in fallow land the loss of 

 nitrates is greater than in land covered with plant growth. 



Thus from an immaniired field at Rothamsted, kept fallow and free 

 of weeds, the loss of nitric nitrogen per acre per annum was for three 

 successive years 38.9, 48.3 and 27.4 pounds respectively, while from 

 an experimental wheat field at the same place the similar loss, as an 

 average of 19 years, was in one case 9.1 and in the other 11.9 pounds 

 per acre^^ per annum. 



The Efect of Mineral Fertilizers on the Loss of Nitrates and on 



Nitrification. 



I have already mentioned the effect of lime and plaster on nitrifica- 

 tion; still another point needs mention. 



The nitrifying organism cannot multiply except in the presence, 

 among other elements, of phosphoric acid and potash. Nitrification 

 is, accordingly, aided by applications of mineral fertilizers. 



The effect of potash salts alone, or of potash salts mixed with car- 

 bonate of lime, in increasing nitrification and ammonification in soils 

 rich in humus, has been shown by Dumont.^^ In soils differently 

 treated the amount of nitric nitrogen produced in 1000 grams of soil 

 in 40 days was in milligrams as follows: 



Check, 2.8 



Potassium carbonate, 0.1 per cent., 57.8 



Unleached ashes, 0.5 per cent., 19.0 



Muriate of potash, 0.1 per cent., and carbonate of lime, 2 



per cent., 38 . 



Muriate of potash, 0.1 per cent., and Thomas slag, 5 per 



cent., 41.5 



Carbonate of lime, 2 per cent., 5.3 



From the preceding it is seen that a marked increase of nitrates 

 resulted when some form of potash was used. In the mixture of 

 muriate of potash and carbonate of lime, a double reaction between 

 the two took place, producing carbonate of potash and chloride of 

 calcium. The author claims that the action of the potash salts is to 

 combine with the humates of the soil and form a compound which is 

 very readily nitrifiable. 



Again, the ability of a crop to utilize the nitrates of the soil is 

 considerably diminished when there is a deficiency of available 

 mineral constituents, especially of potash and phosphoric acid. 



The effect of mineral salts upon nitrification and the loss of nitrates 

 is well shown in the following table:"' 



2:{_.;. -1902 



