98 



Lime Requirements of Certain Suiln 



The Relative Values of Calcium Oxide and Carbonate for Soil 

 Neutralisation. 



Attentioji has already been called to the essential difference in 

 action between oxide and carbonate when added to neutral soils, the 

 former exercising a specific effect. In the case of soils lacking in lime 

 this difference was not distinctly evident, but on account of having in 

 most cases applied a large excess of carbonate it was difficult to draw 

 fair comparisons with these soils. It was evident however that in the 

 case of the Woburn and Craibstone soils, the net effect of the two forms 

 of lime was approximately the same and it was decided to carry out pot 

 experiments in order to bring out this similarity if possible. 



Small glazed earthenware pots were tilled with equal quantities 

 (3 kilos) of Woburn acid soil and various dressings of calcium oxide and 

 carbonate (in equivalent quantities) were made, in each case in duplicate. 

 The soils were watered after treatment and in order that crop growth 

 should not be limited by lack of potash and ])hosphates, an addition 

 of 0-5 grm. of potassium phosphate (neutralised in solution to litmus) was 

 made to each pot of soil. After being allowed to stand in a moist con- 

 dition for about seven weeks, the soils wei'e stin-ed up, barley seed was 

 sown and the plants allowed to grow to maturity, that is, about fourteen 

 weeks from the date of sowing. From germination onwards Uttle 

 difference was perceptible between the effect of the two forms of lime 

 and this was also borne out by the actual weights of the plants when cut. 

 These dry weights and relative weights are included in Table IX and 

 are also plotted in Curve 4. 



Table IX. The Relative Values of Oxide and Carbonate when 

 applied to Woburn acid soil. 



Crop, Barley. 



