103 
may be remembered that Lawea and Gilbert, a by a very careful examination of soils 
to considerable depths, by methods which were also exceedingly sensitive and accu- 
rate, found 17 pounds per acre of soluble nitrogen in soil supporting a crop of alfalfa, 
and 103 pounds, or more than six times as much, in soil where while clover was 
growing. To explain such discrepancies will require further and more comprehen- 
sive investigations. 
Agriculture demands and deserves all the investigation which is being given to it; 
it is in need of, and is worthy of, all the investigators whose services are being 
devoted to this greatest of all our industries; but let us remember that it is only a 
genius who can draw correct conclusions from incomplete data or insufficient prem- 
ises, that we are to use all obtainable information to guide us, and that we are to 
work together as a unit for the betterment of American agriculture. The work is 
greater than any man or any office. Let every man develop and magnify the line 
of work which he is called upon to perform, but let us neither decry nor ignore nor 
underestimate the value of any other good work. 
And God speed the time when we shall agree on some fundamental principles, and 
when \ve shall discover and demonstrate the best and most economic methods for 
the permanent maintenance or increase of the productive capacity of our soils, not 
only by maintaining the most suitable physical conditions of the soil and by effecting 
the utmost possible control of soil water and by the most economic utilization of the 
virgin fertility already stored in the soil, but also, wherever necessary and profitable, 
by liberal additions to the soil of valuable plant food; not by the purchase and use 
of sodium nitrate, almost certainly not, but undoubtedly by the assimilation and 
utilization of unlimited quantities of atmospheric nitrogen; probably not by the use 
of acid phosphates, containing 6 per cent of phosphorus and 60 per cent of manufac- 
tured land plaster, usually supplying, as commonly practiced, less than one-half of 
the phosphorus actually removed by the crops and stimulating the soil to give up a 
greater quantity of the stock of plant food it contains, thus leaving it in a still more 
impoverished condition, but much more likely by returning to the land in pure form 
the bone meal produced on the farm and by using, together with farm manures and 
leguminous green fertilizers, large quantities of fine-ground rock phosphate direct 
from the almost inexhaustible natural phosphate deposits in our Southern States, as 
has already been done with marked profit, and greater promise, by the Ohio b and 
Maryland c experiment stations; and possibly not by using mixed manufactured fer- 
tilizers containing from 2 to 4 per cent of potassium, but by making the most complete 
use of the comparatively large amounts of potassium contained in the straw and 
stover and other coarser parts of our farm crops and in farm manures, by making 
much greater use than we now do of the immense store of potassium contained in 
our heavy clay subsoils, or, if necessary, by using concentrated potassium salts direct 
from the German mines, or what may ultimately prove to be more economical and 
certainly more unlimited, by recovering on our arid coasts, as they are now doing in 
southern France, potassium salts from the inexhaustible supply of the sea. 
In closing, I beg to assure you that no spirit of captious criticism has prompted the 
preparation of this paper. The field is old, but the work is new, and it is being 
prosecuted by many widely separated and almost independent investigators. My 
one purpose iij pointing out some specific differences or disagreements is to bring 
about a more perfect harmony among us, hoping thus that we may avoid the criticism 
and win the more complete confidence of that rapidly increasing class of progressive, 
educated, and even college-bred American farmers who are not only watching closely 
the progress of our work, but who are already putting our teachings to the practical 
test. Not infrequently these well-trained and well-educated farmers are prepared to 
repeat our tenth-acre plat experiments upon a 100-acre field and with a consequent 
percentage accuracy which may even exceed our own. 
To more fully appreciate the tremendous importance of this work, we need only to 
bear in mind the fact that agriculture is no longer merely a means of obtaining a liv- 
ing, but it is now a real business enterprise, and the business of agriculture, especially 
throughout the great Central West, is rapidly taking its rightful rank as an industry 
which may be managed and controlled with a good measure of scientific accuracy. 
The American farmer has a right to expect that, if he adopts the methods which we 
advocate, the fertility of his soil is secure, that the productive capacity of his land 
will be increased, or, at the very least, that it shall be permanently maintained — not 
a Investigations at Rothamsted Experimental Station, IT. S. Dept. Agr., Office of 
Experiment Stations Bui. 8, p. 82; also Agricultural Investigations at Rothamsted, 
U. S. Dept. Agr., Office of Experiment Stations Bui. 22, p. 115. 
6 Ohio Sta. Bui. 184, pp. 94-98. 
« Maryland Sta. Bui. 68, pp. 18-24. 
