170 EEPOET OF THE COMMISSIONER OF AGEICULTURE. 



(4) Whetber a soil is barren simply because there is too little of it; or, 

 (;*) WLether it is unproductive simply because a tbin sui'face soil rests on a stiff 

 clay subsoil of great deptb. 

 (6) What is tbe relative productiveness of different soils? 



OBJECTS AND INTERPEETATION OF SOIL ANALYSIS. 



For a very full discussion of the objects and iuterpretatiou of soil 

 analysis the reader is referred to an article on this subject in the Ameri- 

 ciiii Journal of Science, vol. 22, pp. 183-197, by Prof. E. W. Hilgard, 

 iis v.L'll as to the report on "Soil investigation," by the same author, 

 contained in the "General discussion of the cotton production of the 

 United States," Tenth Census of the United States, 1880, vol. v, pp. 

 G7-8L, of which the following is a summary : 



The claim of soil analysis to practical utility has alvraya rested on the general sup- 

 jioHitiou tbat, " otbcr things being equal, productiveness is, or should be, sensibly 

 IHoportional to the amount of available plant food -within reach of the roots during 

 the period of the i)lant's development;" provided, of course, that such supjjly does 

 not exceed the maximum of that whick the plant can utilize when the surplus simi»ly 

 remains inert. This statement is, either tacitly or expressly, admitted by all those 

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

 perience 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 bo 

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

 fluoric acids to vrater charged with carbonic acid, as used by Dr. D. D. Owen, the 

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

 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 cultivate 

 them. 



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

 under Wolff's initiative, by the consecutive extractions with acid solvents of differ- 

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

 hydrofluoric acids, affords little or no clue 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 colamn of unintelligible names does 

 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 theiroriginal 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 and on which 

 no manures have been applied. The virgin soil and its vegetation are the outcome of 

 long ages of coadaptation 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 "pox^lar" or tulip tree, is at once selected as sure to be both 

 ])roductivo and dui'able, especially if the trees be large. The black and Sp.-uii.sh 

 oaks frequent only " strong soils," and an admixture of hickory is likewise beneficial ; 

 tlie occurrence of the scarlet oak lowers the land, and that of pine still more so, in the 

 estimation of the settler. 



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

 to the farmer ? What are "high " and " low" percentages of each ingredient inipor- 

 tiuit to the plant, whether as food or through its physical properties V 



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

 be high percentages of plant food when analyzed by the method given elsewlit i'. 

 show a high degree of productiveness. This question can bo unqualifiedly ans^\ citd 

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

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

 converse is true, and tbat low percentage indicates low production. 



For instance, we may have a heavy alluvial soil of high percentages and producing 

 a maximum crop in favor.able seasons. If this soil be mixed with its own weight, or 

 even more, of coarse sand, thereby reducing the percentage one-half or less, it will not 

 produce a smaller crop, but is more likely to iiroduce the maximum crop every year, 

 on account of improved physical conditions. K we compare the root system of the 



