30 



who have attempted to interpret soil analyses, and agrees with the accumulated ex- 

 periences of agriculturists. 



Many attempts have been made to find solvents that shall represent correctly the 

 action of the plant itself on the soil ingredients, in order that conclusions might be 

 made as to the present agricultural value of a given soil. From sulphuric and hy- 

 drofluoric acids to water charged with carbonic acid, as used by Dr. D. D. Oweu^ 

 the acid solvents have all signally failed to secure even an approximation to the re- 

 sult desired, viz, a consistent agreement between the quantitative determination of 

 the plant food found in the several soils, and the actual experience of those who cul- 

 tivate them. 



The ultimate analysis of soils, as attempted by the German experiment stations, 

 under Wolffs initiative, by the consecutive extractions with acid solvents of differ- 

 ent strengths, beginning with distilled water, and ending with boiling sulphuric or 

 hydrofluoric acids, affords little or no clew to their agricultural value. 



Soil analyses do not, like the assay of an ore, interpret themselves to a layman; a 

 column of figures summing up to 100 or nearly so, opposite another column of unin- 

 telligible names d*oes not convey much information to a farmer. 



In Europe, and in the thickly settled portions of this country, the arable soils have 

 nearly all been at some time subjected to cultivation, and to the use of fertilizers, 

 thus veiling their original characteristics and rendering extremely difficult the taking 

 of any sample of soil that shall represent correctly, in all respects, the whole of any 

 large field or district. In the greater portion of this country, however, we are able 

 to procure samples of the virgin soil that even the plow has not touched nor any 

 manures been applied. The virgin soil and its vegetation are the outcome of long 

 ages of coadaption by the process of natural selection ; and the settler is afforded a 

 means of judging of the productiveness and durability of the land based upon the 

 character of its vegetation. 



A soil naturally timbered with a large proportion of walnut, wild cherry, or, as at 

 the South, with the '' poplar" or tulip tree, is at once selected as sure to be both 

 productive and durable, especially if the trees be large. The settler knows well that 

 the black and Spanish oaks frequent only "strong soils," and an admixture of hickory 

 is a welcome addition ; while the occurence of the scarlet oak at once lowers the laud 

 in his estimation, and that of pine still more so. 



Having obtained the percentage composition of a soil, how are we to interpret these 

 percentages to the fanner? What are " high" and "low" percentages of each ingre- 

 dient important to the plant, whether as food or through its physical properties? 



The first question is, naturally, whether all soils, having what experience proves 

 to be high percentages of plant food when analyzed by the method given elsewhere, 

 show a high degree of productiveness. This question can be unqualifiedly answered 

 in the affirmative in regard to virgin soils, provided only that improper physical con- 

 ditions do not interfere with the welfare of the plant. But it does not follow that the 

 converse is true, and that low percentage necessarily indicates low production. 



For instance, we may have a heavy alluvial soil <>f high percentages and produc- 

 ing a maximum crop in favorable seasons. If this soil be mixed with its own weight, 

 or even more, of coarse sand, thereby reducing the percentages one-half or less; and 

 yet it will not only not produce a smaller crop, but it is more likely to produce the 

 maximum crop every year, on account of improved physical conditions. If we com- 

 pare the root system of the plants grown in the original and in the diluted soil, we will 

 find the roots in the latter more fully diffused, longer, and better developed, not con- 

 fined to the crevices of a hard clay, but permeating the entire mass, and evidently 

 having fully as extensive a surface contact with the fertile soil particles as was the 

 case in the original soil. How far this dilution may be carried without detriment 

 would varj with different plants and soils, and must largely be a matter of experiment. 

 A plant capable of developing a very large root surface can obviously make up by 

 greater spread for a far greater dilution than one whose root surface is in any case 



