TO WHAT EXTENT SHOULD A SOIL BE LIMED. 373 



still be considered as normal, and that liming' becomes decidedly 

 necessary when the assimilable lime content sinks below 0.20%. 



Various authors place the minimum limit of lime in the soil 

 for good returns at \%. Others state that clay soils with less 

 than o.$% of lime are very much benefitted by liming. Hilgard 

 considers the minimum percentage for the normal crop, o. \% 

 of lime in sandy soils, and 0.3% of lime in heavy clay soils. 



D. Meyer did not take into consideration the necessity of 

 liming in cases in which the magnesia content of the soil was 

 larger than t/ie lime content. This is, hozvever, a very important 

 point. 



In order to furnish an illustration of the importance of the 

 ratio between the lime and the magnesia content of the soil, the 

 following experiments were made : 



From the soil of a field that had not been manured for four 

 years, all particles smaller than 0.25 mm. were separated in the 

 air dry state by a sieve. The amount of fine earth thus obtained 

 was 43.94^0- The amounts of easily assimilable lime, magnesia 

 and phosphoric acid in this fine earth were determined by treat- 

 ment with hot concentrated hydrochloric acid. The analysis 



gave the following data : 



Hygroscopic water '7-39/o 



Humus 1 1.40 ,, 



Lime 0.48 ,, 



Magnesia 0.44 ,, 



Phosphoric acid o. 16 ,, 



Meyer s method for determining the amount of assimilable 

 lime applied upon the same fine earth, yielded less than one- 

 fourth of that obtained by the determination with hydrochloric 

 acid. As regards the determination of magnesia by the applica- 

 tion of Meyer s method, ammonium magnesium phosphate was 

 obtained but in such small traces that it could not be weighed. 



On the basis of the above result I prepared from the soil 1 

 three mixtures, in which the ratio of assimilable lime and 

 magnesia 2 was as follows : — 



1 This soil contained 0.27% potassa, as former analyses had shown. 



2 I had intended to apply powdered magnesite for increasing the amount of magnesia 

 necessary for Pot No. IV., but unfortunately I could not procure that preparation and 

 had to use the precipitated product of commerce, which consists of exceedingly fine 

 particles', too fine for a critical comparison. 



