136 
NITROGEN IN THE COWPBA CROP. 
A table has been prepared which shows the percentage of nitrogen and the total 
nitrogen contained in the crops grown. 
Percentage of nitrogen <ni<1 total nitrogen in crops grown. 
Box, 
Check 
Nitrate of soda, 1 gram 
Nitrate of soda, 2 grams 
Dried blood, 1 gram 
Dried blood, 2 grams 
•Sulphate of ammonia, 1 gram 
•Sulphate of ammonia, 2 gram 
Manure, 1 gram 
Manure, 2 grams 
Average 
nitrogen in 
crop. 
Percent. 
2.282 
2.257 
2.185 
2. 393 
2.188 
2. 345 
2. 314 
2.380 
2. 365 
Average 
nitrogen in 
crop. 
Grams. 
3. 287 
3. 590 
3. 664 
3.949 
3.683 
3.518 
3.703 
3. 626 
4. 029 
Average of 
applied ni- 
trogen 
available. 
P( r cent. 
18.9 
66.2 
19.8 
23.7 
20.8 
33.9 
37.1 
The first point of importance to be observed is that a very considerable crop was 
obtained without the addition of nitrogen, and second, that there was an increase in 
the total nitrogen in the crops of all of the groups upon which nitrogen had been 
applied, though even in the greatest increase the yield was but slightly higher than 
was that in the group upon which no nitrogen had been added, or that the readily 
available nitrogen did not encourage the plant to make an extensive use of other 
sources of nitrogen. 
Another point of importance was also shown, namely, that in the case of the solu- 
ble nitrate and ammonia, and of organic nitrogen in dried blood, the smaller quantity 
seemed to influence the yield to a greater extent than the larger quantity. In the 
case of the manure there was an increase from the larger quantity. In other words, 
the slowly available manure nitrogen yielded more to the cowpeacrop than the con- 
centrated and highly available nitrate and ammonia nitrogen. This is just the reverse 
of the results obtained in a study of the availability of these materials for the non- 
legumes. 
The tabulation also shows that the crop itself was proportionately richer in nitro- 
gen on the series where only 1 gram of nitrogen was applied. While these points 
are interesting and useful the point of greatest importance was to determine whether, 
under all these conditions, the plant was capable of appropriating its nitrogen from 
the air and the influence of the growth of the plant upon the nitrogen content of the 
soil. This involved a chemical examination of the soils previous to and after the 
crops were grown. The analysis of the soil previous to the planting of the crop 
showed that each box contained 54.94 grains of total nitrogen. The seed used and 
the water applied to each box during the season of growth contained 115 milograms, 
or a total of 55.055. 
The accompanying table has been arranged and shows the exact conditions in refer- 
ence to the changes that took place in the nitrogen content of the soils during the 
experiment and the amounts actually contained when the crops were harvested. 
