MANURE, YIELD AND SOLUBLE SALTS IN SOILS. 39 



the current, flowing over the surfaces of the grains in the 

 coarse soil, must have been greater and this would tend to 

 faille the concentration to be less. 



If it is true that the soils which absorb the largest amounts 

 of the essential plant foods, carrying them within and about 

 their granular units, only retain them, after such absorption 

 has taken place, in conditions which permit these ingredients 

 to pass again into solution when conditions- change, such a re- 

 lation would appear to be in harmony with the observed rela- 

 tions of yield on such soils. 



AMOUNTS OF WATER-SOLUBLE SALTS ADDED TO THE 8 SOIL 



TYPES WITH THE DIFFERENT QUANTITIES OF MANURE 



APPLIED. 



A colorimetric determination was made of the water-soluble 

 salts which could be recovered from the manure used in the ex- 

 periments here under consideration and the results found, after 

 washing a quantity of the manure during three minutes in dis- 

 tilled water, are given below : 



Readily water-soluble salts recovered from fresh cow durty with 



distilled water. 



In parts per million of dry matter. 



The gravimetric determinations for potash, limp, magnesia 

 and phosphoric acid cited on p. 24 showed that there was pres- 

 ent in the manure 2.327 times as much potash as was recov- 

 ered in the brief treatment with distilled water; 5.244 times as 

 much lime; 2.764 times as much magnesia; and 2.758 times 

 as much phosphoric acid, as HPO 4 . 



In the next table there are given the amounts of readily 

 water-soluble salts which were added to the different soil types 

 with the manure, on the basis of the analysis of the manure, 

 and taking into account the amount of moisture present in the 

 soil when the manure was added. 



