CALCIUM OXIDE (QUICKLIME). 141 



contained in humus assimilable by plants thus modifies the flora and 

 the yield of cultivated land ; plants of poor nutritive value, such as 

 mosses, heather, reeds, and rushes, disappear, vphilst delicate meadow- 

 plants — leguminosae and gramineas — are greatly developed. A peaty- 

 soil after liming is rapidly converted into arable land. But if liming 

 is a very desirable operation it is very exhaustive to the soil. The or- 

 ganic matter which forms a nitrogenous reserve for the plant rapidly 

 disappears under its action. Fresh reserves must therefore be brought 

 on to the land, as farmyard dung, if regular and satisfactory yields are 

 to be obtained. Soils deficient in lime are generally poor in phosphoric 

 acid ; thus liming should be accompanied by phosphatic manures, for the- 

 effect of lime would not be perfect if any element necessary to the plant 

 was deficient in the soil. Besides lime not only decomposes the humus, 

 it transforms certain minerals rich in fertilizing elements ; the clays 

 which contain potash, for example, are converted into double silicates. 

 of alumina and lime and soluble potash. At the same time the lime 

 acts on the neutral sulphates in chemical manures, fixing the sulphuric 

 acid and bringing the nutritive elements into a more assimilable form, 

 such as sulphate of iron, sulphate of potash, sulphate of ammonia. 

 Lime greatly modifies the soil with which it is incorporated, it gives- 

 strength to light land because the humate of lime agglutinates the- 

 earthy particles together ; strong soils are rendered more friable and 

 wet soils sufficiently dry. Yet all the benefits of liming disappear if 

 used in too great amount. Viala found by trials on the vine that lime 

 in excess produced symptoms of chlorosis whilst small amounts ap- 

 plied gradually yield a luxurious vegetation. 



Muntz and Girard find it more preferable to apply lime in small 

 doses every three years than to apply large quantities at longer intervals. 

 The amount of lime to apply varies with the composition of the soil 

 and its depth. Liming should always be done in autumn. A soil' 

 to be fertile should contain a minimum of 3 per cent of carbonate of 

 lime and even 5 per cent in clay soils. On granite soils it is necessary to- 

 apply 10-12 hectolitres of lime per hectare (11-13-2 bushels per acre), 

 whilst on soils rich in organic matter 20-24 hectolitres (22-26-4 bushels- 

 per acre) must be applied. Friable soils only require 15 hectolitres (16| 

 bushels per acre), heavy soils 20-30 hectolitres (11-33 bushels per 

 acre), and peaty soils 35 hectolitres (38^ bushels per acre). The- 

 following is the method to pursue in liming land : The quickUme is 

 laid down directly on the fields in heaps of 20-50 Htres (4-4-11 gallons)- 

 and the heaps covered with a layer of soil. In three weeks the lime- 

 is completely converted into hydrate. The lime is then spread uni- 

 formly over the ground and then harrowed into the soil so as to mix, 

 it intimately therewith. This method is the simplest and quickest. 

 A manure rich in nitrogen and in lime is made by slaking lime in 

 composts where the lime is mixed with farmyard dung, organic matter, 

 farm waste, etc. Three weeks afterwards the whole is covered with 

 earth. If watered frequently slaking is finished in a few months, and 

 the lime so obtained may be spread on the land and mixed with the 

 soil. 



Action on Plants. — Milk of lime is a strongly alkaline product. 



