No. 4.] MANURIAL PROBLEMS. 153 



tried u})on liinod iiiul uiiliiucd soil for grass. Hoth wero 

 (.•omparativclv of very slight value u|)()n the uiilinied land, 

 and upon limed soil the raw aluniiiuiin phosphate appeared 

 to have been possibly injurious. The ignited phos])hate, on 

 the contrary, proved upon the limed land iiearl}' as effective 

 as some of the most valuable of the i)hosphates. 



In recent vears trials have been made of a lai'jje number 

 of different kinds of plants, in the course of which the 

 ignited iron and aluminum phosphate has invariably been 

 far more helpful ui)on the limed soil than upon that which 

 remained unlimed ; nevertheless, maxinmm crops of ordinary 

 garden crops were not obtained, especially in the case of 

 turnips, beets, cabbages, summer squashes and other plants. 

 To be sure, the results that have been joroduced in recent 

 3^ears have been brought aliout very largely as a result of the 

 residual effect of former applications. When it is remem- 

 bered, however, that at its best upon limed soil no distinct 

 advantage of the ignited iron and aluminum phosphate over 

 certain of the superphosphates was obtained, the comparative 

 inferiority of this material in its subse(|uent action with most 

 hoed crops, even upon limed land, coupled with its practical 

 worthlessness upon acid unlimed soil with practically all of 

 the crops with which it has been tried, excepting possibly one 

 or tw^o of the millets, is enough to condemn the "reverted" 

 phosphoric acid in this material as of inferior value for most 

 purposes. 



It is to be presumed that ujion lying in the soil the ignited 

 phosphate gradually takes on some of the water which has 

 been driven out artificially, whereby it loses some of its 

 earlier efficiency as a manure. When it is recognized that 

 acid soils, deficient in or wholly devoid of carbonate of lime, 

 are common in Massachusetts, Rhode Island and other sec- 

 tions of the country, and that upon such soils the ignited 

 iron and aluminum phos})hate may be practically worthless, 

 the matter assumes unusual im})ortance. This is especially 

 true in view of the fact that this [)articular phosphate is said 

 to find its way into certain ready-mixed commercial fer- 

 tilizers in considerable quantities. It is supposed that it is 

 used even by manufacturers who derive most of their phos- 



