EXPERIMENT STATION BULLETINS. 



595 



T.\JBLE 3.— QUANTITIES OF PHOSPHORIC ACID IN SOIL EXTRACTS IN PARTS PER MILLION ON SOILS. 



(a) 1st leachings — 2 day period. 



(b) 2nd leachinga — 15 day period. 



Table 3 shows some remarkable results. All the treatments, excepting 

 CaSO^ on soils No. 1 and 2, second leachings, greatly increased the 

 quantities of P found in the soil extracts. Of the non-phosphate treat- 

 ments NaXOg heads the list in efficiency followed in order generally by 

 hydrated lime, NaCl, KCl, CaCOs and CaSO^. Considerable variation 

 exists between individual results which may indicate different forms or 

 conditions of P in the soils. KCl and XaCl liberated more P from the 

 acid than the alkaline soils, while the reverse is true for hydrated lime. 

 The acid soils did not retain as much P from Ca(HoP04)o as did the alka- 

 line soils. It is also remarkable that in five cases out of the eight NaNOg 

 treated soils gave up more P to the extract than when treated with acid 

 phosphate. No apparent relationship exists between these results and 

 the total P or that soluble in N/5 HCl as given in Table 1. 



TABLE 4.— QUANTITIES OF SULPHUR TRIOXIDE IN SOIL EXTRACTS IN PARTS PER MILLION ON SOILS. 



(a) Ist leachings — 2 day period. 



(b) 2nd leachinga — 15 day period. 



These results show that S compounds soluble in water under condi- 

 tions of the experiment are quite completely removed in the first leach- 

 ings, even when CaSO^ is added to the soils, however, not all of the S 

 is reclaimed in the two leachings. This is also true of CI and NO3 added 

 in salts. Sulfates appear to be more easily removed from acid than 

 from alkaline soils. 



