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in increasing the amount of available plant food. Some manures, on 

 the other hand, exert mainly, if not entirely, an indirect action. Such 

 a manure is Lime. Although lime forms part of the food of plants, 

 the amount required is so small that practically no cultivated soils do 

 not contain sufficient to supply the immediate needs of their crops. For 

 this reason it is considered that the good effect of an application of 

 lime to most soils is due entirely to its indirect action. Lime affords 

 an excellent example of the different ways in which the fertility of a 

 soil can be increased indirectly. Lime exerts a mechanical effect upon 

 the soil. It improves the texture of clay land by removing the sticki- 

 ness, thereby rendering it powdery and more readily acted upon by 

 the atmosphere. A simple experiment will demonstrate this action. 



Take a quantity of stiff clay and divide it into two. With one por- 

 iion mix a little lime, and make both portions up into a stiff paste. 

 Leave in the sun to dry. When dry, note that the portion that re- 

 ceived no lime is very hard and ' cakey' while the other crumbles down 

 when touched. Applying this principle to practice, it will be seen 

 that if clay land be well limed, the atmosphere w 11 have a much bet- 

 ter chance of doing its work. On the other hand, when lime is applied 

 to light sandy soils, it acts as a cement, binding the coarse particles 

 of sand together. This accounts for its use in making mortars 



The other effects of lime are of a chemical nature, (i) rji)ne frees 

 potash. The potash in the soil is bound up in very insoluble com- 

 pounds, upon which the lime is able to act chemically, turning out the 

 potash and placing it, as it were, at the disposal of the crop (ii) Lime 

 helps on the decomposition ofcegetable matter by securing the best condi- 

 tions for fermentation, (iii) Lime sweetens sour landhj counteracting 

 the acids produced by the decay of vegetable matter. If these acids 

 accumulate, as they will in a badly drained soil, the land becomes sour ; 

 this sourness can be lemoved by an application of lime, (iv) The pre- 

 sence of lime in the soil, as has already been stated, is a necessary con- 

 dition of nitrification. 



Lime can be applied to the soil in several forms. Marl and chalk 

 spread over the soil produce good results, but the form most suitable 

 for application is slaked lime which has been exposed to the atmos- 

 phere for some time. When limestone or chalk is heated in a limekiln, 

 carbonic acid gas is driven off, and the substance left is quicklime. This 

 form is unsuitable for application to the land on account of its caustic 

 nature. It is readily converted into slaked lime by adding water. 

 Slaked lime is still somewhaf caustic and apt to cause the burning up 

 and loss of organic matter. Therefore slacked lime should be exposed 

 to the air ; carbonic acid gas is absorbed, and the substance formed 

 does not differ in composition from the original limestone, but it is in 

 a powdery condition convenient for application. Deficiency of lime in 

 a soil is usually due to its tendency to sink. This should be a guide 

 to the cultivator in applying it. Lime should be kept as near to the 

 surface as possible, and therefore spread over the land rather than dug 

 in. Although lime is ins tluble in pure water, rain water has sufficient 

 carbonic acid gas in it to dissolve it, and when dissolved the lime must 

 percolate downwards, since it is not absorbed by the plant roots. Other 

 salts, much more soluble than lime, also pass into solution, but they 



