824 



HOW CROPS FEED. 



The results were as follows, for 1,000 j^arts of extract, 



1.579 



"We see that each successive extraction removed from 

 the soil a scarcely diminished quantity of mineral mat- 

 ters, including phosphoric acid. In case of a poor soil, 

 we should not expect results so striking, as regards quan- 

 tity of dissolved matters, but doubtless tliey would be 

 similar in kind. 



This is shown by the investigations that follow. 



Ulbricht gives ( Vs. St.^ V., 207) the results of the simi- 

 lar treatment of four soils. 1,000 grams of each were 

 put in contact with four times as much pure water for 

 three days, then two-thirds of the solution was poured off 

 for analysis, and replaced by as much pure water; this 

 was repeated ten times. Partial analyses were made of 

 some of the extracts thus obtained ; we subjoin the pub- 

 lished results : 



Dissolved by 40,000,000 parts of water from 1,000,000 parts of— 

 Loamy Sand from Heinsdorf. 



