INVESTIGATION ON THE FORAGING POWERS OF SOME 

 AGRICULTURAL PLANTS FOR PHOSPHORIC ACID. 



L. H. Merrill. 



Several years ago Professor Balentine, then agriculturist of this 

 station, began a series of experiments for the purpose of determin- 

 ing the "foraging power" of certain plants for phosphoric acid. The 

 results then obtained were published in the annual report of this 

 station for 1893. 



These investigations were considered of such importance that after 

 Professor Balentine's death the work was extended and continued. 

 Eight species of plants were chosen, representing four orders: peas 

 and clover (Leguminosae) ; turnips and ruta bagas (Cruciferae) ; 

 barley and corn (Gramineae; ) tomatoes and potatoes (Solanaceae). 

 The plants were grown in the forcing house in wooden boxes, four- 

 teen inches square and twelve inches deep,each containing 120 pounds 

 of sand. This sand was obtained from a knoll near by, and having 

 been taken from a depth of three or four feet was nearly free from 

 organic matter. It was found to contain a very little phosphoric 

 acid, but the total amount present was so far below what would be 

 required by a vigorous plant that it is doubtful if its presence could 

 be considered a disturbing factor. Owing to its almost complete in- 

 ertness and its inability to puddle or pack, this soil has proved a very 

 satisfactory medium, and was thought preferable to the mixture of 

 sphagnum and coal ashes sometimes used in pot experiments. 



Three forms of phosphates were used: 



A. Acidulated Florida rock, containing 20.60 per cent, total phos- 

 phoric acid; 14.97 per cent, soluble; 3.70 per cent, insoluble; 16.90 

 per cent, "available." 



B. Crude, finely ground Florida rock (Floats,) containing 32.88 

 per cent, phosphoric acid. This was obtained from the commercial 

 ground rock by stirring it with water, allowing the coarser particles 

 to subside and then pouring off the turbid water. The "Floats" are 

 the sediments deposited from these washings. 



C. A phosphate of iron and alumina, containing 49.58 per cent, 

 phosphoric acid, a large part of which, 42.77 per cent., was soluble in 

 ammonium citrate. This ready solubility in ammonium citrate is 

 brought about by roasting the phosphate. It undergoes a 



