VALUE OF HUMATES AS PLANT FOOD 9 1 



oxygen, and inasmuch as plants obtain these elements 

 from water and from the carbon dioxide of the air, 

 no value was assigned to humus. Later, investigators 

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

 when combined with the humus and before under- 

 going fermentation, was of no value as plant food. 



Recent investigations have proved that the phos- 

 phoric acid and other mineral elements combined 

 with the organic matter of soils are of value as plant 

 food, 17 and it has been demonstrated that crops grown 

 on the black soils of Russia obtain a large part of 

 their mineral food from organic combinations. 84 . Cul- 

 ture experiments have shown that under normal con- 

 ditions plants like oats and rye may obtain their min- 

 eral food entirely from humate sources. Seeds when 

 planted in a mixture of pure sand and neutral humates 

 from fertile soils, produced normal plants. In order to 

 secure the best conditions for growth, a little lime 

 must be present to prevent the formation of humic 

 acid, and the organisms found in fertile fields must 

 also be introduced. The following example is given 

 of oats which were grown when the only supply of 

 mineral food was in humate forms. 



NITROGEN AND ASH ELEMENTS. 17 



In. six oat In six mature 



seeds. plants. 



Gram. Gram. 



Nitrogen 0.0040 0.0556 



Potash 0.0013 0.0640 



Soda o.ooor 0.0079 



Lime 0.0002 0.0249 



Magnesia 0.0005 o.oi 10 



Iron 0.0064 



Phosphoric anhydride 0.0016 0.0960 



Sulphuric anhydride o.ooor 0.0090 



Silicon 0.0026 0.7300 



