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A question of great importance at the present time, and which is properly receiving 
more attention than any other that has to do with the maintenance of soil fertility, 
is the question of the utilization by crops of atmospheric nitrogen and of its accumu- 
lation in the- soil. The fact has been established that the members of the legume 
family of plants do have the power under proper conditions of absorbing and using 
in their own development the nitrogen of the air. The question next of importance 
from the standpoint of soil improvement and maintenance is whether the supply of 
nitrogenous plant food in the soil has any influence in determining the condition 
of soil in reference to proportion or amount of nitrogen that may be appropriated by 
this class of plants, and further the effect of their growth under different conditions 
of soil supply of nitrogen upon the nitrogen content of the soil, as well as the sub- 
sidiary question of the relative value of the nitrogen so appropriated for the nourishment 
of the nonlegumes. 
The method of investigation used in the study of these points is here outlined. A 
soil was employed that contained an abundance of phosphoric acid and potash, and 
was, moreover, rather light in character, a condition that would favor the decay of 
organic substance. This soil originally consisted of equal parts of weight of shah; 
and quartz sand, and contained 0.09842 per cent of nitrogen in the air-dry state. 
This soil was used for vegetation experiments during three seasons, and at the end (if 
that time the soil nitrogen had diminished very considerably. After these experi- 
ments the soils from the several boxes were thoroughly mixed and inoculated with 
soil from an area upon which cow peas had been grown, and on which the nitrogen- 
fixing bacteria were present, and 160-pound portions were weighed off and placed in 
each of the several boxes. Hence, there was in each box a medium sandy soil, rich 
in mineral plant food. Nitrogenous manures were added or withheld according to 
the following plan of study: 
(1 ) The study of the source of nitrogen to cowpeas under the following conditions: 
(a) The addition of no nitrogen. 
(b) The addition of different amounts of nitrate nitrogen. 
(c) The addition of different amounts of dried-blood nitrogen. 
(d) The addition of different amounts of ammonia nitrogen in ammonium 
sulphate. 
(e) The addition of different amounts of cow-manure nitrogen. 
(2) The availability of cowpea nitrogen, as compared with nitrate, organic, 
ammonia, and manure nitrogen for the growth of nonlegumes. 
(3) The possible accumulation of nitrogen in cultivated but uncropped soils. 
The wooden boxes used here were numbered from 1 to 57, both inclusive, and only 
the first 30 were employed during the first season. Accordingly they received: 
Boxes 1, 2, 3, nothing. 
Boxes 4, 5, 6, 1 gram of nitrogen as nitrate of soda. 
Boxes 7, 8, 9, 2 grams of nitrogen as nitrate of soda. 
Boxes 10, 11, 12, 1 gram of nitrogen as dried blood. 
Boxes 13, 14, 15, 2 grams of nitrogen as dried blood. 
Boxes 16, 17, 18, 1 gram of nitrogen as ammonium sulphate. 
Boxes 19, 20, 21, 2 grams of nitrogen as ammonium sulphate. 
Boxes 22, 23, 24, 1 gram of nitrogen as in solid and liquid manure. 
Boxes 25, 26, 27, 2 grams of nitrogen as in solid and liquid manure. 
Boxes 28, 29, 30, nothing, and kept bare. 
The fertilizers and manure were applied to the respective boxes July 5, 1902; 20 
seeds of black-eyed cowpea were planted in each box, with the exception of 28, 29, 
and 30, and 8 quarts of w r ater were added to supply the initial moisture. 
The growth during the season was fairly uniform. At the end of the summer the 
cowpeas were harvested, dried, and ground, and after aliquot portions were taken 
for analysis the ground material was kept dry in the laboratory. In the spring of 
1903 millet was planted in the several boxes which had been treated as follows: 
Boxes 1-27, inclusive, received each the corresponding cowpea crop of 1902. 
Boxes 28, 29, 30 received no application of nitrogen. 
Boxes 31, 32, 33 received 1 gram of nitrogen in nitrate of soda. 
Boxes 34, 35, 36 received 2 grains of nitrogen in nitrate of soda. 
Boxes 37, 38, 39 received 1 gram of nitrogen in dried blood. 
Boxes 40, 41, 42 received 2 grains of nitrogen in dried blood. 
Boxes 43, 44, 45 received 1 gram of nitrogen in sulphate of ammonia. 
Boxes 46, 47, 48 received 2 grams of nitrogen in sulphate of ammonia. 
Boxes 49, 50, 51 received 1 gram of nitrogen in solid and liquid manure, fresh. 
Boxes 52, 53, 54 received 2 grams of nitrogen in solid and liquid manure, fresh. 
Each box received May 29, 1903, 1 teaspoonful of barnyard millet seed, but the 
germination being poor another teaspoonful of millet seed was added about ten days 
later. 
