42 T. Lyttleton Lyon and James A. Bizzell 



in the planted tanks than in the implanted ones and has been discussed 

 in the publication referred to above — the fact still remains that the 

 comparison between different crops is all based on the same unplanted 

 soil as a standard and such comparison is confined to the same season. 

 There seems to be every reason, therefore, why the results of such com- 

 parison, if not quantitatively exact, should at least be qualitatively 

 significant. 



It is apparent from table 20 that there is considerable difference in 

 the quantities of nitrogen taken up by these crops, ranging in the above- 

 ground parts from 144 pounds per acre in maize to 46 pounds in the mixed 

 grasses. It is to be noted also that there is more nitrogen in the drainage 

 water from the soil on which the crops which absorbed much nitrogen 

 grew, than in the drainage from the soil producing crops containing little 

 nitrogen. Certain plants use a greater quantity of soil nitrogen than 

 do others, without decreasing the quantity of nitrates in the drainage 

 water. In this respect maize exceeds oats, and oats exceed the grasses. 

 In the paper cited above it is suggested that some plants have the property 

 of depressing the formation of nitrates, and that some plants possess this 

 property to a greater degree than do others. The data here presented 

 are in line with such an hypothesis. 



The last column of table 20 shows that the tanks producing maize, 

 oats, and clover have more nitrogen in the crop plus drainage water 

 than is contained in the drainage water from the corresponding unplanted 

 tanks, while the tanks in which timothy and mixed grasses were raised 

 have less nitrogen in the crop plus drainage water than is contained in 

 the drainage water of the corresponding unplanted tanks. If it is assumed 

 that these plants obtained all their nitrogen from nitrates and that nitrate 

 formation proceeded at the same rate in the planted and the unplanted 

 soils, there would appear to be more nitrates produced in the soil of the 

 maize, oats, and clover tanks than in the unplanted soil, indicating a 

 stimulation of nitrate formation under these crops. To oppose this 

 theory there is, of course, the possibility that these plants obtained part 

 of their nitrogen in some form other than nitrates. It is known that 

 clover takes nitrogen from the air, and it is known also that maize and oats 

 can utilize organic nitrogen in certain forms. On the other hand, the 

 smaller quantity of nitrogen in the crop and in the drainage water of the 

 soil producing timothy and mixed grasses as compared with the drainage 



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