EXPERIMENT STATION BULLETINS. 591 



soils. Oue is led to conclude tliat the effects of neutral salts in liber- 

 ating K from rocks and soils depend upon the chemical and physical 

 state of the K in these materials. 



The situation with respect to liberation of P from soils by various 

 treatments is similar to that of K, however, the results of investigators 

 show that P in certain compounds is made more soluble while that in 

 other forms is not affected. Wagner (31) was probably the first to 

 show that NaNOg dissolved phosphates in the soil; while Liebig (20) 

 and Lawes and Gilbert (21) seem to have observed that ammonium 

 salts increased the solubility of soil phosphates. The quantity of 

 water soluble phosphates in soils was not increased by lime or gyp- 

 sum, Bradley (4). Greaves (12) in an extensive investigation of 

 this problem observed that the solubility of phosphates is decreased 

 in general by Ca and Fe salts, but that Na^SO^, CaSO^, (NHJoSO^, 

 NH^Cl and NH^NOg increase their solubility; while the solubility of 

 calcium phosphates was increased and of iron phosphates decreased by 

 NaNOg and KINOg. This same author states that the effect of MgSO^, 

 NaCl, MgCL and KCl, varies with the kind of phosphate, but the sol- 

 vent action of all compounds is more vigorous in presence of the soil. 

 Cameron and Bell (9) working on pure compounds give data to show 

 that lime salts depress the solubility of lime phosphates, while neutral 

 salts and acid solutions have the opposite effect, also, that hydrolyzing 

 salts increase the solubility of iron and aluminum phosphates and neutral 

 salts have only a slight action on them. Hartwell and Kellogg, (15), 

 Kellner (17) and Sutherst(28) claim that lime increases the solubility 

 of soil phosphates. The last named author and Gaither (13) state that 

 lime is especially eff'ective on iron and aluminum phosphates. CaCOg 

 is not effective in dissolving phosphates, Sutherst (28) ; and Lyon and 

 Bizzell (19) found no relationship between liming soils and P removed 

 from them by cropping or leaching. While considerable difference of 

 opinion prevails among investigators it appears that soil P may be 

 made more soluble by the common fertility treatments. 



Kesearches have repeatedly shown that other soil elements may be 

 dissolved by various treatments. Ca and Mg may be lost from the soil 

 in considerable quantities through fertilization as shown by Collinson 

 and Walker (7), references cited by Lyon and Bizzell (19), Wheeler 

 (32), the work of Cameron and Bell (10) and many others. That 

 NaNOg, NaCl, and Na.SO^ increase the solubility of CaCOg in soils has 

 been shown by Breazeale (2). Studies on adsorption and basic ex- 

 change in soils by numerous authors prove beyond doubt that Ca, Mg, 

 Fe, and Al are liberated in soils by certain neutral salt treatments. 

 The work of Monmier and Luczyaskt (25) is especially interesting in 

 this connection because they state that CaCOg and MgCOg precipitate 

 Fe in the soil as a basic carbonate which gradually changes to a hydrate 

 and little is found in the soil extract. In general, experimental data 

 appear to indicate that the results obtained depend somewhat upon the 

 materials used and quantities of reagents added to them. 



The Prohlem. 



The composition and concentration of soil solutions as affected by 

 soil ti'eatments is undoubtedly of great importance in practical agri- 

 culture. King (18) and more recently Burd (3), Stewart (27), Hoagland 



