97 
parties interested in selling nitrates, certainly justifies calling special attention to 
this marked disagreement among scientists as to the wisdom or economy of purchas- 
ing nitrogen for the use of legumes. 
The agricultural experiment stations are becoming more and more responsible for 
the methods of soil management which are being practiced in thiscountry. We stand 
as the guardian of the fertility of American soils. If leguminous crops do not obtain 
sufficient atmospheric nitrogen, is it not our business to discover why they do not. 
and then to advocate a system of soil treatment or soil management which shall 
enable legumes to obtain from the free and absolutely inexhaustible supply of the 
atmosphere all of the nitrogen which they need for maximum yields? By proper 
inoculation we have grown a crop of alfalfa which contained as high as seventeen 
times the quantity of nitrogen which was contained in a crop grown without inocu- 
lation, but otherwise under exactly the same conditions and in soil which last year 
produced more than 60 bushels of corn per acre. 
Director Thorne, of the Ohio Experiment Station, unquestionably one of our most 
careful and exact agricultural investigators, has fully demonstrated during the past 
dozen years that a five-year rotation of corn, oats, wheat, clover, and timothy, when 
grown on certain Ohio soils, does not secure sufficient atmospheric nitrogen for 
maximum crops. He has also obtained abundant proof that the purchase and use 
of commercial nitrogen in that rotation, either alone or in combination with other 
elements, is attended with financial loss, as will be seen from the following data 
taken from the recently issued Ohio Station Bulletin No. 141: 
Fertilizers for wops grown in fire-year rotation in Ohio. 
Soil 
plat 
num- 
ber. 
Plant food applied. 
Nitrogen 
Phosphorus 
Potassium 
Nitrogen, phosphorus 
Nitrogen, potash 
Phosphorus, potash 
Nitrogen, phosphorus, potash 
Nitrogen, phosphorus, potash 
Nitrogen, phosphorus, potash 
Nitrogen, phosphorus, potash 
Cost of 
plant 
food in 
fivevears 
$12. 00 
2.40 
6.50 
14.40 
18. 50 
8.90 
20. 90 
2(5. 90 
14.30 
7.70 
Wooster field. 
Value of Profit ( + ) 
increase, or loss (— ). 
$5. 64 
11.40 
4.44 
22. 05 
6.24 
16.57 
27.83 
28. 97 
22. 70 
15. 57 
-%. 36 
+ 9.00 
- 2.06 
+ 7.65 
-12.26 
+ 7.67 
+ 6.93 
+ 2.07 
+ 8.40 
+ 7.87 
Strongsville field. 
Value of Profit ( + ) 
increase, or loss ( — ). 
$0. 57 
14.56 
.53 
16. 76 
2.50 
14. 35 
19.98 
20.33 
17. 02 
10. 22 
-$11.43 
+ 12.16 
- 5.97 
+ 2.36 
- 16.00 
+ 5.45 
- .92 
- 6.57 
4- 2.72 
+ 2.52 
It will be observed that on these Ohio soils commercial nitrogen used alone, or 
w r ith potassium only, has produced an increased yield sufficient to pay less than 50 
per cent of the cost of the nitrogen used. When used in connection with phosphorus, 
or with both phosphorus and potassium, it has not increased the yield above that 
produced by the phosphorus alone, or by the phosphorus and potassium together, 
sufficient to pay for the cost of the nitrogen used. As a matter of fact no other treat- 
ment has produced a net profit equal to that resulting from the use of phosphorus 
alone. To be sure we have larger yields from other applications, but Ave must bear 
in mind that it is not large yields that we desire, but large profits. (Large yields 
remove large quantities of plant food from the soil. ) 
What shall we say then? Shall we advise farmers to buy commercial nitrogen for 
use in this rotation? Or shall we rather advise them to grow a catch crop of stock 
peas or soy beans with the corn or a crop of clover with the oats, or, if necessary, to 
add another full leguminous crop to their rotation? 
A recent contribution « from the U. S. Department of Agriculture, Bureau of Chem- 
istry, suggests and offers some experimental data in support of the suggestion that 
a chemical analysis of the soil might be made each year in order to ascertain the 
amount of available plant food contained in the soil and the consequent kinds and 
quantities of fertilizers to be added for the more certain production of the crop 
desired. 
The opinion is advanced *> ' ' that the mineral plant food which a plant does take 
up is that which existed in the soil in an assimilable form at the time of planting." 
The cost of determining the assimilable, or available, plant food and the necessary 
laboratory equipment is described, and the statement ( ' is made "that samples (of 
soil) could be brought to such a laboratory and four days later the results could be 
« Jour. Amer. Chem. Soc, 24 (1902), p. 79. 
21736— No. 142—04 7 
&Ibid., p. 106. t'lbid., p. 98. 
