346 SOILS. 



amounts than in "poor" lands; thus materially reducing the 

 expense of fertilization. The high production and durability 

 of such lands therefore amply justify their higher pecuniary 

 valuation; for which there would be no rational permanent 

 ground if they required fertilization to the same extent as 

 poor lands. In other words, if the entire amount of soil-in- 

 gredients removed by crops had had to be currently replaced 

 equally in all cases (as is implied in the hypothesis, advanced 

 by some, that the chemical composition of soils is of no prac- 

 tical consequence), the high prices which from time imme- 

 morial have been paid for black prairie and rich alluvial lands 

 as against meagre uplands and barrens, would have been so 

 much money wasted. 



The explanation of these advantages evidently lies largely 

 in the larger amounts of soil ingredients annually rendered 

 available in rich soils by the fallowing effect of the atmospheric 

 agencies, because of .the generous totals present. The actual 

 amounts of soil ingredients thus rendered accessible to plants, 

 other things being equal, are evidently more or less directly 

 proportional to the totals of acid-soluble plant-food ingredients 

 present. And if this is true in cultivated lands, the inevitable 

 conclusion is that the same must be true of virgin lands; whose 

 productive capacity and duration can therefore be forecast by 

 such analyses. It will be observed that the above data, which 

 could be indefinitely increased by corroborative analyses, seem 

 to establish the fact that about one per cent of acid-soluble 

 potash, one of lime, the same, or less, of magnesia, and .15% 

 of phosphoric acid, are thus shown to be " high " percentages 

 of these ingredients in virgin soils. 



It is not easy to see how the above conclusions can be suc- 

 cessfully controverted ; they are, moreover, thoroughly in ac- 

 cordance with cultural experience. Difficulties of interpreta- 

 tion arise mainly in the case of medium soils, which show 

 neither very high nor very low percentages of plant-food ; and 

 which raise the question of what amount or percentage con- 

 stitutes " adequacy " of each of the several substances. 



Low Percentages. On the other hand, whenever in virgin 

 soils acid-analysis shows the presence of but a very small pro- 

 portion of one or several of the essential ingredients, we have 



