THE ANALYSIS OF VIRGIN SOILS. 367 



Nos. 1 39 and 171 are heavy black prairie soils of high productive capa- 

 city, whose production had, at the time of sampling, lasted almost un- 

 diminished for over twenty years. Nearly the same is true of the two 

 California soils, Nos. 499 and 1113; which, however, are ferruginous 

 loams of only moderate clay-content. In all, the percentage of phos- 

 phoric acid shown by the analysis is at or below the recognized limit 

 of deficiency, while the lime-content of all is as high as is required for 

 the welfare of any soil, however constituted. The potash-percentage 

 also is low in all except the "red foothill soil," No. 1113. 



Passing to the soils of low lime-content, we find the two Mississippi 

 soils, poor in both potash, lime and phosphoric acid, so low in produc- 

 tion as to be wholly unprofitable in cultivation without previous ferti- 

 lization ; No. 559, from California, produced two fair crops of barley 

 and then no more. No. 207, is the soil of Eel river bottom, California ; 

 profusely productive at first, by virtue of its high content of both potash 

 and phosphoric acid ; but " giving out " under a few years' culture of 

 clover or alfalfa (which draw heavily upon lime), and quickly restored 

 to productiveness under the influence of dressings of quicklime. In 

 this case the soil had become acid, a condition which always militates 

 against the success of culture plants, and more especially against those 

 of the leguminous relationship. 



What are Adequate Lime Percentages? We have in the 

 presence or absence of the natural vegetation peculiar to cal- 

 careous soils (" calciphile ") an excellent index of the pres- 

 ence or absence of such amounts of lime carbonate as fulfil the 

 conditions of its beneficial effects. Lists of such plants for the 

 United States are given farther on ; they agree almost through- 

 out with such plants as are everywhere recognized by Ameri- 

 can farmers as indicating productive soils. 



All soils bearing such vegetation show with red litmus paper, 

 when wetted, a neutral reaction at first, which after the lapse of 

 twenty or thirty minutes turns to a blue alkaline one; such as 

 is given under the same conditions by the carbonates of lime 

 and magnesia. 



But the reverse is not necessarily true; for we occasionally 

 find soils containing considerable amounts of lime carbonate 

 that yet fail to bear lime vegetation. This is the case of ex- 

 tremely heavy clay soils, as exemplified in the table below 

 in the case of the last three soils; while the first, No. 220, ex- 



