No. G. DEPARTMENT OF AGRICULTURE. 685 



of practice. There are soils so deficient in. some one element of plant 

 food that safe inferences concerning fertilization may be drawn from 

 the results of analysis, but these are not the common arable soils of 

 the country. The chances always are that a chemical analysis would 

 rot prove helpful to a farmer. It probably would show the presence 

 of a large amount of every element of plant food, andthere informa- 

 tion would cease. In practice one may know that the eoil is lacking 

 in available fertility, while nothing in the results of analysis would 

 indicate such a fact. 



Another scheme of fertilization was based upon the composition 

 of tlie crop to be produced. The number of pounds of nitrogen, phos 

 phoric acid and potash in a ton of potatoes is known, and it appeared 

 reasonable that a fertilizer should approach the compoisition of the 

 crop desired. This theory of fertilization is now discreddted by lead 

 ing scientists and by practical farmers, for two reasons: First, it faile 

 to take into account the tons of available plant food in the soil. Land 

 that has been given a heavy growth of clover, or a dressing of stable 

 manure, may contain all the available nitrogen needed for the pro 

 duction of a full crop, while there is lack of potash or of phosphoric 

 acid. The soil may be naturally so rich in potash that a score of 

 crops would not exhaust the supply appreciably, and yet be lacking 

 in available nitrogen or phosphoric acid- — a lack not apparent from 

 analysis of the soil, but apparent from results obtained when one 

 of these elements is supplied to the growing plant. 



The other reason for discrediting this theory is the rather awkward 

 fact that experimentation shows profitable results from the seem- 

 ingly excessive use of certain elements under some circumstances. 

 A soil may be in fairly productive condition, and then give more net 

 profit from a crop treated with twice the amount of one element 

 found in the composition of that crop than it would from a lighter 

 application, and at the same time another element may not increase 

 yields at all. These puzzling results do not destroy our faith in the 

 value of scientific investigation, but they assure us that the laws 

 governing plant growth are not within our grasp in such degree 

 that we can feed crops by any general formula prepared by others 

 with assurance that we are doing the most profitable thing for our- 

 selves. After turning to one and to another, we finally must de- 

 pend upon ourselves and our own experimentation. 



Station Kesults. — I state the matter of self-dependence thus be- 

 cause many are loth to give up the hope that others can save them 

 from the trouble of farm experiments. They should understand 

 that, so far as scientific research has gone, there is no way to know 

 absolutely wiiat fer'tilizers will pay best on a potato crop, or other 

 crop, except by farm tests. And yet there are certain wide lines, 

 fixed by Station results, within which we may confine our labors, and 

 thus keep the chance of failure down to a minimum. 



