EXPERIMENT STATION BULLETINS. 849 



mately have to be decided in the field, using the plant as indicator. All 

 that is claimed is that the freezing point method, as a laboratory method, 

 seems to indicate the true lime requirement of the soil. By true lime re- 

 quirement is meant the maximum specific activity that the different soils 

 have for lime. In this maximum lime requirement there is included the 

 lime that is necessary to neutralize any free soluble acids and acid salts, 

 and the lime that the soil requires to satisfy its absorption-adsorption 

 properties. Now it is possible that this method indicates altogether too 

 high lime requirement and when the plants are used as indicators it 

 might be found that the plants can make just as good growth with 

 smaller amounts as they can with the maximum. Oil the other hand it 

 should be strongly emphasized that this method does not give altogether 

 too abnormally high lime rebuirements. Indeed the maximum amounts 

 indicated are quite in accord with some of the maximum applications 

 that many soil authorities advise. Thus Hopkins^ states: "It may be 

 said, however, that 10 tons of ground limestone per acre would not only 

 do no harm, but would probably produce somewhat larger crops than 

 any lighter application. As much as 10 tons per acre has been applied 

 on an experiment field in southern Illinois, and the crop yields on that 

 field have been larger during the last three years than on any other ex- 

 periment field in that area. Two to four tons per acre, however, have 

 usually produced much benefit." 



In a recent publication by Blair^*' the following statements are made 

 in regard to the amounts of lime that might be applied to New Jersey 

 soils: "With general farm crops on a loam to clay loam, 1,500 to 2,000 

 pounds of burned lime may be considered a moderate application. For 

 alfalfa, 2,500 to 3,000 pounds could safely be used. For sands and sandy 

 loams, 1,000 to 1,500 pounds would be a safe application. If the soil is 

 known to be very acid or to contain a great deal of organic matter, a 

 somewhat heavier application could be made," etc. Further on he says : 

 "On wet land and muck lands as much as 5,000 to 10,000 pounds of 

 lime may be required to correct the acidity." 



It is evident, therefore, that the maximum lime requirements indicated 

 by the freezing point method certainly appear to be in accordance with 

 some of field practices. 



THE ABSORPTION OF NaOH, KOH. AND NH4OH BY SOILS. 



In the last section the absorption of Ca(0H)2 by different soils was 

 considered. It will now be of great interest to ascertain the absorption 

 by the same soils of other bases, namely KOH, NaOH, and NH^OH. The 

 absorption of these bases by the various soils represented in Table 5 was 

 determined exactly in the same way as that of Ca(0H)2 already con- 

 sidered. The solutions of these hydrates were diluted to such an extent 

 that their freezing point depression was about the same as that of 

 Ca(0H)2 — a little over .100° C. Their strength, however, was determined 

 by titration and the necessary calculations made therefrom. Table 8 con- 

 tains the amount of these bases taken up by the same soils used in the 

 case of Ca(0H)2. The quantity absorbed is expressed in number of c. c. 

 of the hydrate per 2 grams of soil. For convenient and direct compari- 

 son the required Ca(0H)2 by the same soils is also reproduced in this 

 table. 



(9) Soil Fertility and Permanent Agriculture, 1910, p. 173. 

 (10) Circular 54, New Jersey Agr. Expt. Sta., 1916. 



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