620 J ouDuil of Agriculture, Victoria. [loOcx.. 1912. 



Burnt and slaked lime give very finelv divided carlmnatf of lime in a 

 soil because of the chemical action of slaking. Lime added as carbonate 

 (ground limestone) is always more active the more finely it is ground. 

 With this material it is recommended that at least 35 per cent, should 

 pass a sieve with 10.000 meshes to the square inch. Fineness of grinding 

 becomes more important when the quantity applied is small. 



The Soil Loses Lime. 



Under natural conditions there is a marked tendency for the supply 

 of carbonate of lime to diminish in the surface soil. Carbonate of lime 

 is practically insoluble in pure water, but in water containing carbonic 

 acid it goes into solution as bi-carbonate, which forms the chief ingredient 

 in the drainage waters from many soils. Again, a certain quantity is 

 removed in farm crops, while earth worms in certain cases contribute by 

 graduallv ' burying the coarser fragments. The use of certain manures 

 such as superphosphate and the potash salts, and notably sulphate of 

 ammonia, gradually deplete the soil in carbonate of lime. The combined 

 result of these withdrawals may be verv considerable, and it is estimated 

 that certain of the experimental fields at Rothamsted ha\-e lost from the 

 surface soil during the past 32 vears carbonate of lime at the rate of 800 

 to 1,050 lb. per acre per annum. 



It is an old saying that " lime sinks in the soil.'' So much is this the 

 case that even soils on the limestone formation may be found to require a 

 fresh application of lime at the surface. 



nuANTiTv OF Lime Required in Soils. 



Di-scussing the percentage of carbonate of lime required in soil. Hall* 

 places the danger limit between \ and h per cent. Judging from numei'ous 

 analyses of Victorian soils made by the Department, it is apparent that 

 the great majority of them fall into the category of soils which require 

 lim.e. Notable exceptions are found in the Mallee and in the dark soils 

 of the Wimmera. 



When is Liming Necessary? 



Chemical analysis can tell wiien a soil requires lime, because the per- 

 centage of carbonate of lime falls too low. It is a less sure guide as to 

 when a .soil does not require lime, becau.se the carbonate of lime present 

 may exi.st in relatively large lumps. 



Clay and peaty soils require more lime to be present than do sandy 

 soils low in organic matter to maintain them in good working order. 



Litmus paper is stained blue with a vegetable colouring matter. Acids 

 change the blue colour to red. If a little soil is placed on litmus paper, 

 mo'stened. and left standing for a few minutes, the soil mav be washed 

 oft' and the paper examined. If the paper is clearly reddened, this indi- 

 cates that the soil is aciH and requires lime. But a soil may require liming 

 when it fails to give the acid test. 



There are limits to the usefulness, therefore, both of chemical analysis 

 and of the litmus test, when we inquire whether or not a soil requires 

 lime. The surest way to know is to make trial applications of lime, and 

 watch the results. This matter will be referred to later on. "Meanwhile 

 it may assist to an understanding of the effect of such applications if we 

 proceed to consider some of the more important actions exercised by lime 

 upon the soil and crop. 



* Jour. Bd. Agric. I>oik1., 1906. 



