IV. THE REAL VALUE OF "NATURAL PLANT 



FOOD."* 



SUMMARY. 



Within the past year the sale of a material called " Natural 

 Plant Food " has been vigorously pushed among the farmers of 

 this State. Extravagant and misleading claims have been made 

 for its value as a plant-food. 



The guaranteed analysis implies, and a specific claim is made, 

 that the material is "all available to plants in the soil." Chem- 

 ical analysis at this Station shows that the materials are mostly 

 in unavailable forms as plant-food. An average of three samples 

 shows the following composition: 



Total pliLspboric acid 22.21 per cent. 



Insoluble phosphoric acid 20.81 per cent. 



Available phosphoric acid 1.40 per cent. 



Potash soluble in water . 13 per cent. 



" Natural Plant Food " is really a mixture of some rock phos- 

 phate (probably Florida soft phosphate) with glauconite, a min- 

 eral containing potash in an insoluble form, commonly known as 

 " green sand marl." 



The selling price of " Natural Plant Food " varies usually from 

 $25 to |28 a ton; its real agricultural value as plant-food is prob- 

 ably below $10 a ton at a liberal estimate. 



INTRODUCTION. 



For some months past numerous inquiries have been addressed 

 to this Station asking for information in regard to a fertilizing 

 material, the sale of which was being vigorously pushed. The 

 following extract from one of these letters is an indication of 

 the contents of many others : " We are in trouble over this fer- 

 tilizer and would like to know just what it is. It is sold to the 



♦Published also as Bulletin No. 108. 



