ix.] LIMING 265 



phosphates of aluminium or iron which are present in 

 many soils, and, by converting them into phosphate of 

 lime, renders the phosphoric acid more available for 

 the plant. 



Besides its specific actions in thus rendering more 

 soluble the soil constituents which nourish the plant, 

 lime exerts a very beneficial action by maintaining 

 the neutral reaction of the soil ; it neutralises the acids 

 produced by the decay and nitrification (see p. 174) of 

 the organic matter in the soil, or those due to the 

 oxidation of materials like iron pyrites in other soils 

 (see p. 243). Again, as has been shown already, it 

 is necessary as a base to satisfy the requirements of 

 artificial manures like sulphate of ammonia, superphos- 

 phate, and kainit (see p. 216), or to prevent the soil 

 being invaded by such organisms as the destructive 

 fungus causing " finger-and-toe " (see p. 209). It must, 

 however, be clearly realised that lime is wanted as a 

 base, not as a compound of calcium, necessary though 

 calcium itself may be to the economy of the plant ; and 

 that only carbonate of lime (chalk, limestone, etc.) or 

 quicklime and slaked lime, which promptly become 

 carbonate of lime when incorporated with the soil, are 

 capable of acting as the required base. Other calcium 

 compounds, as superphosphate of lime or sulphate of 

 lime (gypsum), or phosphate of lime in bones, etc., are 

 either acid or neutral, and do not supply the base 

 required to effect the beneficial actions set out above; 

 they cannot replace lime or chalk — in fact, they do not 

 contain any " lime " in the farmer's sense. Unfortunately, 

 it has been too often supposed that the use of artificial 

 manures, such as superphosphate of lime, removed the 

 necessity of a periodical liming of the soil, and some 

 of the neglect into which this all-important operation 

 has fallen may be set down to the unfortunate confusion 



