Apr. 15, i9i8 Soil Acidity as Influenced by Green Manures 



n9 



Table V. — Alkalinity and atnmonia production in soils by green manures 

 [Results expressed as the calcium-carbonate equivalent for 20 tons of dry manure] 



Material. 



Decrease 

 in limestone 

 require- 

 ment. 



Control soil 



Legume mixttires: 



Soybean 



Canada field pea 



Sweet clover 



Alfalfa 



Red clover 



Hairy vetch 



Subaverage 



Nonlegtime mixtures: 



Wheat 



Rape 



Oats 



Com 



Rye 



Timothy 



Redtop 



Sorrel 



Subaverage 



Bamyard-mantrre mixture 



Grand average 



Pounds. 



1.593 

 2,543 

 2,503 

 2,473 

 3,950 

 2, 420 



2,580 



1,135 

 1,377 

 4,244 

 2,942 



2,503 

 2,033 

 1,870 

 4. 004 



2,511 



1,457 



Ammonia 

 equivalent. 



Pounds. 



3,970 



5, 212 

 4,455 

 3,941 

 2, 770 

 4,056 



4,067 



5,069 

 6,840 

 4,398 

 3,884 



528 

 827 



3,536 



2, 242 



2, 468 3, 662 



Ash alkali 

 equivalent. 



Pounds. 



2, 768 



3, 120 



2, 108 

 3,128 

 2, 252 

 1,308 



2,447 



2, 400 



4, 192 



2, 140 



1,880 



508 



928 



640 



1,468 



1,769 



2, 208 



2, 070 



In the average case, therefore, the nitrogen in the added manure 

 would suffice to work the obser\^ed change if it v.ere fully converted to 

 ammonia within the brief period of two weeks. On the other hand, the 

 ash constituents of the manure would, even though completely liberated, 

 not suffice to work the obserA^ed change. 



There are exceptions to these deductions from averages. In the cases 

 of red clover, rye, timothy, redtop, and sorrel, the ammonia equivalent 

 to the total nitrogen of the green manures would not suffice to effect the 

 observed change. Indeed, in the case of the rye, the alkali equivalent of 

 the rye, nitrogen, and ash together would not account for the entire 

 change observed. 



Moreover, there is little probability of so complete conversion of the 

 manurial substances within two weeks as this comparison requires. 



Some notion of the behavior of this acid soil with respect to the fer- 

 mentative process of ammonifi cation is afforded by the studies of Dr. 

 G. C. Given, of the Pennsylvania Station. He found that the soil of 

 plot 32 (the source of the soil used in the present experiment), first ster- 

 ilized by heat and then moculated by the bacteria from neighboring fer- 



