76 



T. Lyttleton Lyon and James A. Bizzell 



tity of nitrates when the samples were taken and the quantity at the end of 

 ten days. The column showing the quantity of nitrates at the end of 

 twenty daj^s has not had the original nitrates subtracted. 



TABLE 25. Nitrification in Soil under Alfalfa and under Timothy 



Plat 



Crop 



Soil treatment 



Nitrates 

 produced 



in ten 



days 



(parts per 



million) 



Nitrates 

 in soil at 



end of 



twenty 



days 



(parts per 



million) 



4001 A 



4002 A 



4001 C 



4002 C 



Alfalfa.. 

 Timothy 



Alfalfa. . 

 Timothv 



Limed. . . 

 Limed. . . 

 Not limed 

 Not limed 



176 



145 



92 



77 



381 

 361 

 148 



148 



It appears from the results here tabulated that the alfalfa soil, both when 

 limed and when not limed, has a capacity for converting ammonia into 

 nitric acid more quickly than does the timothy soil. This is indicated by 

 the results at the end of ten daj^s. At the end of twenty daj's, however, 

 the crop factor did not affect the total production of nitrates, at which 

 time there had accumulated about all the nitrates that the nitrifying 

 organisms were capable of producing in the presence of their own products. 



The character of the plants growoi may therefore affect the rate of nitri- 

 fication but not the limit of nitrate accumulation in the soil. The former, 

 however, is of greater importance than the latter, as, under field conditions, 

 nitrates are constantly being removed by plant roots or by drainage water 

 and the supply for the growing crops depends on the rate at which lutrates 

 are being formed. 



Another test of nitrification m the soil previouslj" under these crops was 

 made on July 6, 1910. The samples for this test were taken from the bare 

 strip on each plat. The results are stated in Table 26. 



Nitrate formation is greater in each case in the soil which previously 

 grew alfalfa than in the soil on which timothy had been grown. 



In 1911 tests of nitrate formation in the soil under the crops and also in 

 the bare strips on these plats were made. Samples were taken to a depth 

 of eight inches on May 10, May 29, and November 8. In Table 27 are 



