187 
Income and outgo of the nitrogen in the box soils. 
Series. 
1 
2 
3 
4 
5 
G 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
121 
22 
23 
24 
25 
26 
27 
28 
29 
30 
Original- 
ly pres- 
ent. 
Nitrogen 
in seed 
and 
water. 
Grams. 
Grams. 
54.94 
0.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54. 94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
■ 54. 94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.115 
54.94 
.04 
54. 94 
.04 
54.94 
.04 
Nitrogen 
in fertil- 
izer or 
manure. 
•1.00 
1.00 
1.00 | 
2.00 
2.00 
2.00 
1.00 
1.00 
1.00 
2.00 
2.00 
2.00 
1.00 
1.00 
1.00 
2.00 
2.00 
2.00 
1.00 
1.00 
1.00 
2.00 
2.00 
2.00 
Total ni- 
trogen 
present at 
the begin- 
Present 
in soil at 
the end 
of the 
Average. 
ning of 
the lirst 
season. 
first sea- 
son. 
Grams. 
Grams. 
Grams. 
55. 055 
61.48 
| 
55. 055 
62.44 
} 61 . 50 
55. 055 
60.58 
j 
56. 055 
60.82 
1 
56. 055 
60.58 
\ 59. 38 
56. 055 
56. 94 
J 
57. 055 
61.00 
| 
57. 055 
60. 82 
)■ 60.13 
57. 055 
58.58 
j 
56. 055 
58.16 
| 
56. 055 
59. 82 
} 58.81 
56. 055 
58.44 
j 
57. 055 
64. 62 
1 
57. 055 
56.98 
} 60. 72 
57. 055 
60.56 
J 
56. 055 
56.54 
1 
56. 055 
61.02 
V 59. 05 
56. 055 
59.60 
j 
57. 055 
58.42 
] 
57. 055 
56.52 
I 57. 45 
57. 055 
57.42 
J 
56. 055 
60.70 
1 
56. 055 
57.84 
} 59. 70 
56. 055 
60.58 
1 
57. 055 
61.26 
) 
57. 055 
62.14 
62.27 
57. 055 
64.62 
j 
54.98 
56.12 
1 
54. 98 
58.08 
\ 56. 89 
54.98 
56.48 
I 
Gain in 
soil. 
Grams. 
I 6. 11 
+3. 33 
+3.08 
+2. 76 
+3.67 
+ 3.00 
+ .40 
Nitro- 
gen in 
crop. 
Grams. 
3.29 
3.69 
3.66 
3. 95 
3. 68 
3. 52 
3.70 
+3.65 3.63 
+5.62 ; 4.03 
+ 1.91 
Total 
gain. 
rams. 
9. 73 
6. 9 
6.74 
6.71 
7.35 
6.52 
4.10 
7.28 
9.65 
1.91 
These results show, first, that there was a fixation of nitrogen by the cowpea crop, 
and that this fixation was greater where no nitrogen was applied than in any other 
series, or, in other words, that the soil upon which no nitrogen had been applied 
contained, after the crop of cowpeas had been removed (which crop contained nitro- 
gen equivalent to 6 per cent of the total contained in the soil upon which the crop 
was grown) 6.44 grams, or 11.7 per cent more nitrogen than it contained before the 
plants were grown. This fact has not been heretofore shown, viz, that this plant, a 
member of the legume family, has the power not only of absorbing from the air the 
nitrogen necessary for its own growth, but also in its growth contributes to the stock 
of nitrogen in the soil. In the case of those groups of soils receiving more or less of 
the different kinds and forms of nitrogen the same general conclusion is reached, but 
the important point is that in no case was the absorption of nitrogen from the air 
greatly in excess of that upon plat 1, and in every case the fixation of nitrogen in the 
soil was very much less. Thus in 4, 5, and 6 (1 gram of nitrate), there wan an 
average gain of 6.92 grams of nitrogen in the soil and crop, while in 7, 8, and 9, 
where double the amount of nitrogen was applied (2 grams of nitrate), the total gain 
was only 6.74 grams of nitrogen. Similarly in 16, 17, and 18 (1 gram of sulphate of 
ammonia), there was a total average gain of 6.52 grams, and in 19, 20, and 21 (2 
grams of sulphate of ammonia), there was a total average gain of 4.10 grams of nitro- 
gen. In all of the soils where either nitrate or ammonia was applied the gain was 
much less than in the soils .where no nitrogen salt was applied. This, taken together 
with the fact that the application of the double portion of either nitrate or of ammonia 
resulted in a smaller yield as compared with the single portion, shows clearly that 
the soluble nitrogen exerted a depressing effect on the process of fixation. 
On the other hand, we find that the total average gain in 10, 11, and 12 (1 gram 
dried blood), was smaller than that in 13, 14, and 15 (2 grams of dried blood), the 
corresponding amounts being 6.71 grams and 7.35 grams. In 22, 23, and 24 (1 gram 
of manure), the average total gain was 7.28 grams, and in 25, 26, and 27 (2 grams of 
manure), the corresponding gain was 9.65 grams. Here we find that the less soluble 
organic nitrogen was not detrimental to the fixation of atmospheric nitrogen when 
applied in double the amounts. 
I have given this plan of experimentation and certain of the results mainly for the 
purpose of showing the importance of investigations of this character and the value 
