AQUEOUS SOLUTIOX OF THE SOIL. 31 7 



ranging from 2 to 6 parts in 100,000 of soil. {Jahreshe- 

 richt der Ag. Chem., 18G"), p. ?A.) 



It should be remnrkod that Knop's failure to find phos- 

 phoric acid may depend on the (uranium) method he euj- 

 ployed, a method different from that commonly used. 



Can the Soil-water supply Crops with Food I — As- 

 suming, then, that all the soil-food for plants exists in solu- 

 tion in the water of the soil, the question arises, Does the 

 water of the soil contain enough of these substances to 

 nourish crops ? In case of very fertile or highly manured 

 fields, this question without doubt should be answered af- 

 firmatively. In respect of poor or ordinary soils, how- 

 ever, the answer has been for the most part of late years 

 in the negative. While to decide such a question is, per- 

 haps, impossible, a closer discussion of it may prove ad- 

 vantageous. 



Russell [Journal IIi</hlai>d and ^ig. iSoc., New Series, 

 Vol. 8, p. 534) and Liebig {^Inn. d. Chem. ti. Pharm.., CV, 

 138) were the first to bring prominently forward the idea 

 that crops are not fed simply from aqueous solutions. Dr. 

 Anderson, of Glasgow, presents the argument as follows 

 (his Ag. Chemistry., p. 113): 



" In order to obtain an estimate of the quantity of the 

 substances actually dissolved, we shall select the results 

 obtained * by Way. The average rain-fall in Kent, where 

 the waters he examined were obtained, is 25 inches. Now, 

 it appears that about two-fifths of all the rain which fiills 

 escapes through the drains, and the rest is got rid of by 

 evaporation. f An inch of rain falling on an English acre 

 weighs rather more than a hundred tons ; hence in the 

 course of a year, there must pass off by the drains about 

 1,000 tons of drainage watoi*, carrying with it, out of the 

 reach of plants, such substances as it has dissolved, and 



* On (liaiii-water*, see p "13. 



t From Parke's measurcaicnts, Jour. Roy. Ag. Soc., Eny., Vol. X^'II, p. 137 



