EXPERIMENT STATION BULLETINS. 



473 



15 and 25% moisture. In each of these eight examples, the decompo- 

 sition at 15% moisture is slower in the beginning, and higher in 

 the end than at 25% moisture. Table VIII gives the averages of 

 these eight sets, computed in various ways. The comparison of the 

 rate of nnnnonia-forniation in llic middle section of the table shows the 

 interesting fact that in the last 10 days, the drier soils form about twice 

 as much ammonia i)er day as the moist ones. Indeed, it seems quite 

 doubtful that the dry soil have really reached the endpoint. 



The lower section of the table shows how many jter cents of the total 

 ammonia are produced in the dillerent time intervals. The result can 

 be summarized in the statement that the dry soils produced 38% 

 and 40% of the total ammonia in the first G days while the moist soils 

 produced G9% and G7% in the same time. 



TABLE VIII. 



Ammonia Produced in the Average of four Soils at Various Moistures. 



Daily Ammonia Production. 



Unfertilized . 

 Fertilized . . . 



15^ 

 25/0 



15% 

 25% 



6.8 

 12.0 

 12.7 

 18.0 



8.2 



1.9 



14.6 



4.0 



7.2 

 3.3 

 8.8 

 4.0 



Unfertilized . 

 Fertilized . . . 



Per cents of Total Ammonia Produced at Different Intervals. 



15% 

 25% 



15% 

 25% 



8% 

 18% 



21% 



19% 

 20% 

 18% 

 19% 



11% 

 31% 

 11% 

 27% 



19% 



15% 



24% 



9% 



43% 

 25% 

 36% 

 24% 



The retardation through too thin surface films is also quite evident 

 in the Series VI of the experiments (Table VI) where coarse, medium 

 and fine sand are compared. At the same moisture content, the coarse 

 sand has the thickest surface film, and should therefore show the most 

 rapid decomposition in the beginning. The first section of Table IX 

 proves this point quite conclusively. The fastest decomposition in the 

 coarse sand is during the first two days, in the medium sand, it is 

 best during the second and third day, and the maximum for the fine 

 sand is between the fourth and sixth days. 



TABLE IX. 

 Daily Average of Ammonia irng per 100 cc.) produced by B. mycoides in various sands. 



