io8 



SOILS AND FERTILIZERS 



^. 



nitrogen to the list, but stated that the nitrogen, when 

 combined with the humus and before undergoing fer- 

 mentation, was of no value as plant food. 



"Recent investigations have proved that the mineral 

 elements combined with the organic matter of soils are 

 of value as plant food, 9 and that crops grown on the 



black soils of Russia 

 obtain a large part of 

 their mineral food 

 from organic combi- 

 nations. 84 Culture ex- 

 periments show that 

 plants like oats and 

 rye may obtain their 

 mineral food entirely 

 from humate sources. 

 Seeds when planted 

 in a mixture of pure 

 sand and neutral 

 humates from fertile 

 soils, produced per- 

 fect plants. In order 

 to secure normal con- 

 ditions, a little lime 



was added to prevent the formation of humic acid, and 

 the organisms found in fertile fields were introduced. 

 The following results are given of oats which were 

 grown when the only supply of mineral food was in 

 humate forms : 



Tofa/ /nso/ub/e Matter*: 



FlG. 26. Graphic Composition of 200 Soils, 

 showing the Proportional Amounts of the 

 Various Soil Constituents. 



i. Nitrogen, 

 acid. 



2. Potash. 3. Phosphoric 



