CHEMICAL CHANGES 



EFFECT OF NATURE OF Son, ON PRODUCTION OF NITRATES 



AND AMMONIA. 1 



We find that while these soils varied from 100 to 5 in nitrify- 

 ing capacity, the production of active nitrogen (nitrates and am- 

 monia) varied only from 100 to 70. When the production of 

 nitrates alone is considered, the soils vary greatly, but if nitrates 

 and ammonia together are taken, the differences are much smaller. 

 If nitrates are much more valuable to plants than ammonia, these 

 differences are very important, but if there is little difference in 

 the value of the two, soils under favorable conditions do not 

 vary greatly in their power to supply nitrogen from the same 

 organic bodies. According to Russell 2 plants on cultivated soils 

 probably absorb all their nitrogen as nitrates. There is no doubt, 

 however, but that plants have the power of absorbing ammonia, 

 and that ammonia is present in the soil, though ordinarily it is 

 present only in a small quantity. 



Effect of Chemical Additions to Soil. While carbonate of lime 

 as a rule accelerates nitrification, it has little effect upon the total 

 production of ammonia and nitrates together. Its use may result 

 in the production of nitrates in excess of the needs of the crops, 

 and consequent loss of fertility to the soil. 



Additions of fertilizing materials to the soil (acid phosphate, 

 sulphate of potash) may increase or decrease the production of 

 nitrates, but they have little effect upon the total active nitrogen 

 produced. 



1 Fraps, Texas Station Bulletin 106. 

 ' 2 Soil Conditions and Plant Growth, p. 108. 

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