MANURE, YIELD AND SOLUBLE SALTS IN SOILS. Oi 



of soil than the different amounts of manure have made within 

 the poorer group. The four stronger soils stand higher above 

 the poorer in nitrie acid than 15 tons of manure has been able 

 to increase the nitrates in the poorer soils. 



INFLUENCE OF LARGE AMOUNTS OF MANURE UPON NITRIC ACID IN SOILS. 



In the experiments with 25, 50, 100 and 200 tons of ma- 

 nure per acre on these same 8 soil types additional light is 

 thrown upon the important problem of nitrification in, soils. 



In the next table are given the results found in that investi- 

 gation as regards the amounts of NO 3 which could be recov- 

 ered from the 8 soils. 



Influence of different amounts of manure on the nitric acid content 



of soil. 



Notwithstanding the fact that the five samples for each soil 

 type were identical, that is, taken from the same bulk lot, and 

 had been placed, during 65 days, under entirely similar condi- 

 tions, there came to be a profound difference in the amounts of 

 nitric acid which were recovered from them, and apparently as 

 the result of adding the manure to the soils. 



A strong nitrification had occurred in each and every soil to 

 which no manure was added ; it is therefore clear that, so far 

 as environment was concerned, conditions were favorable for 

 nitrification to go forward. 



The addition of the manure has certainly interfered with 

 the amounts of nitrates recovered from these soils; and it is 

 certain that denitrification (or else absorption) has taken place 

 in all of the soils to which the largest amount of manure was 



