EXPERIMENT STATION BULLETINS. TO:] 



wheat yielded only a small amount of material to solution, its depression 

 being only .020 °C. This depression, however, is the same as that in soil 

 4, which received heavy applications of fertilizers. 



In the Cornell soils in table 12 the same inconsistency and irregularity 

 are shown in the relationship. Soil 1 was unfertilized and yet it yielded 

 as much material to solution as soils 3 and i which received fertilizers. 

 Soils 5. however, which received manure gave the largest amount of solu- 

 ble material, with soil 2 coming second. 



Of all the sets of soils used those of the University of Illinois show 

 the best consistency and regularity between treatment and solubility 

 product. They show that soil 1 which received residual phosphorus and 

 lime gave more soluble material than soil 2 which received only residue. 

 Likewise, soil 4 which received manure, phosphorus and lime yielded a 

 greater concentration than soil 3 which received only manure. Again 

 soils 7 and 8 which received residue phosphorus and lime, and manure, 

 phosphorus and lime respectively, produced more soluble material in the 

 solution than soils 5 and 6 which received only residue and manure respec- 

 tively. And the most important fact is that the order of the magnitude 

 of the solubility product corresponds to the crop-producing power of the 

 soils. On the other hand it must be stated that when an optimum mois- 

 ture content is employed in these soils this fundamental principle is not 

 confirmed, as data subsequently to be presented show. 



In brief then, it can be said that there is no universal and consistent 

 relationship between the factor of solubility and the state of fertility. 

 Hence, the factor of solubility is not always an absolute and reliable 

 criterion of the state of fertility of soils. This conclusion agrees with 

 that already announced in connection with the salt treated soils, and is 

 not at all surprising in view of the various disturbing factors pointed 

 there. This conclusion finds further confirmation in the next phase of the 

 investigation. 



Rate and Extent of Solubility of Experimental Field Soils Which Have 

 Been Receiving Fertilizer Treatments in the TTsual Manner. Moisture 

 ^Maintained at Optimum Content and Soils Kept Mostly Outdoors. 



In the preceding series of experiments the rate and extent of solubility 

 were studied at a very high moisture content, usually at the supersatura- 

 tion point. While it is very important and highly desirable to so investi- 

 gate the subject, yet this condition is artificial and does not simulate 

 practical or field conditions. In the field the moisture content is greatly 

 difl'erent and consequently the rate and extent of solubility may be mucli 

 difl'erent. Before the principles established under the artificial condition 

 can become applicable to field conditions, they must be tested out under 

 field conditions. 



Accordingly, the investigation on the rate and extent of solubility of 

 experimental field soils which have been receiving fertilizer treatment in 

 the usual manner, was repeated under pracdcal conditions. The pro- 

 cedure consisted of placing a certain amount of the fresh soil on a filter 

 paper in the funnel and washing with distilled water until all the free 

 soluble salts of the soil were eliminated. A small sample of this soil was 

 taken, air-dried, and its freezing point depression determined by using 

 15 grams of air dry soil and 10 c.c. of distilled water. The remainder 

 oC the soil was allowed to remain in the funnel undisturbed and to lose 



