80 



Lime Reqiiireiiitiits of Ccrlaiii Soils 



a safeguard against (1) "over-liming" and its undesirable consequences, 

 and (2) the uneconomical utilisation of soil nitrogen. 



When the application of lime is sufficient to impart an alkaline 

 reaction to the soil water, certain other changes appear to be induced. 

 During a number of titration tests with various soils, it was clearly 

 evident that a flocculation of the soil compounds occurred when a 

 slight excess of lime was present, and the time required for the passage 

 of a definite amount of wasli water (200 c.c.) approached a minimum as 

 the partial sterilisation region was reached. This was so noticeable 

 that some readings were taken, and these are plotted along with the 

 titration curve and dry matter production in Curve 2. These data 

 appl}' to llotluirasted soil, but similai- results were also obtained with 

 Millbrook soil. Thus a close agreement obtains between the results of 

 nitrate determinations, tests for protozoa, pot culture experiments and 

 the titration method suggested. 



Totaf of four Crops (dry m&ucr in grmsj. 



0-4 0-5 



per cent. Caleiiim O.xidc applied 



Curvo 2. Showiiij; the EtTeit of an .Ajjplicatioii of t)ie Critical Dose of Calcium O.xido 

 (as indicated by the Titration Method for deterniininj; the Partial Sterilisation Point) on 

 Filtration and on Crop Production. (Rothanisted Soil.) 



