june26, i9i6 Mineral PliospJiates and Plant Nutrition 487 



In 1890 Goessman (2) outlined what has since become a most extensive 

 investigation, concerning the availability of phosphate minerals. In 

 reporting on this work Brooks says (3, p. 104) that — 



It is possible to produce profitable crops of most kinds by liberal use of natural 

 phosphates, and in a long series of years there might be a considerable money saving 

 in depending, at least in part, upon these rather than upon the higher-priced dissolved 

 phosphates. 



Results from a second series of experiments begun in Massachusetts in 

 1897, along the same line as that outlined by Goessman, indicate that 

 phosphatic slag was "exceedingly available for crops, but the Florida 

 soft phosphate was very inferior. For certain crops, South Carolina 

 rock gave surprisingly good returns * * *." 



Prianishnikov (20) states that lupins and peas have a very marked 

 ability to obtain phosphorus from natural phosphate, while wheat and 

 oats must be assisted by the solvent powers of the soil or they can not 

 produce normal crops. Schloessing (22) concludes from his experiments 

 that it is not necessary that phosphate should be in a state of solution, 

 since the roots of plants are able to dissolve the phosphorus compounds 

 without the intervention of water. 



Patterson (18) reports results, based on a study of various phosphates, 

 which indicate that reverted phosphate gave the highest average yield 

 for corn, wheat, and hay. South Carolina rock phosphate produced 

 slightly better yields than bone black, and Florida soft rock phosphate 

 was quite available for wheat. Wheeler and Adams (30, 31, 32) found 

 raw phosphate profitable for peas, oats, crimson clover, and Japanese 

 millet when used on unlimed land ; but for fiat turnips, beets, and cabbage 

 it gave poor yields. They are of the opinion that rock phosphate is likely 

 to be most useful when applied to moist soils rich in organic matter, 

 where legumes, com, and "possibly wheat and oats are to be grown." 



Thome (24, 25), of Ohio, in 1897 inaugurated a very extensive study 

 of the comparative value of raw rock phosphate and acid phosphate used 

 in conjunction with manure. Where, in computing the yields of com, 

 wheat, and clover, he took the average of all the unfertilized plots as a 

 basis for comparison, he reports (24, p. 18) — 



By this method of calculation the average increase on Plots 2 [floats plus yard 

 manure] and 3 [floats plus stall manure] combined is found to be practically the same 

 as that on Plots 5 [acid phosphate plus yard manure] and 6 [acid phosphate plus stall 

 manure] combined, but when the larger cost of the acid phosphate is deducted the net 

 gain is a little greater on Plots 2 and 3 [with raw phosphate]. 



By another method of computing the increase he obtains results less 

 favorable to raw phosphate. 



Truog (27) has demonstrated rather clearly that fann crops are vari- 

 able in their ability to secure phosphorus from difTercnt sources. Nine of 

 the ten crops tested by him made a better growth on aluminum phos- 



