COMMERCIAL FERTILIZERS IN HORTICULTURE. 173 



William C. Strong asked whether the phosphates of iron and 

 -aluminum were undesirable. 



Professor Jordan replied that for the horticulturist they are ; as 

 in his cultural work he had found their action to be too slow. 

 But in farming operations, especially on land about to be laid 

 down to grass, they may be valuable for their staying qualities, 

 as they require much of "Nature's weathering" to develop 

 their useful conditions. 



Benjamin P. Ware asked what was meant bj' the terms " avail- 

 able" and " reverted" phosphoric acid. 



Professor Jordan answered that those expressions represent an 

 important fact. Available phosphoric acid — if such in reality — 

 is that which can be rapidly taken up by growing plants. The 

 term "available," as used in connection with fertilizer analysis, 

 means the sum of the water-soluble and reverted (or citrate-solu- 

 ble). " Reverted " should really be applied only to " that which 

 has once been soluble in water, but by chemical change has gone 

 back;" but is now used in the sense of "that which is soluble 

 in ammonium citrate." 



The question was asked, What is the relative value of wool- 

 waste and hair-waste as compared with other materials in 

 commercial fertilizers? 



Professor Jordan replied that although rich in nitrogen, both 

 are very slow to yield their fertilizing elements, unless they are 

 broken down by chemical treatment or some process other than 

 Nature's weathering ; even then there are other sources which are 

 preferable for the horticulturist. Cotton-seed meal, for this pur- 

 pose, is this year sold in Maine at twenty dollars per ton. This 

 yields six and three-fourths per cent of nitrogen ; two and three- 

 fourths per cent of phosphoric acid, and one and three-fourths 

 per cent of potash. At the price named one can now get a supply 

 of nitrogen from cotton-seed meal more cheapl}' than from any 

 other source. (In the first two formulas given in the paper read 

 today, the term acid phosphate refers to Florida rock. South 

 ■Carolina rock, or bone-black, each in a dissolved state.) 



The next question asked was, What fertilizing elements are 

 <lerived from bones? To this Professor Jordan replied that bone 

 furnishes phosphoric acid and nitrogen. If bones are steamed, 

 that process takes away a portion of the nitrogenous matter, thus 

 reducing the proportion of nitrogen in the fertilizer. 



