222 Fertilisers [pt, hi 



The second difference between lime and chalk is that 

 when added in sufficient quantity quicklime partially 

 sterilises the soil, killing many of the bacteria, protozoa 

 and other organisms^; later on the bacterial numbers 

 rise very considerably^ and produce increased quantities 

 of ammonia and nitrates; this stage coincides with the 

 time at which the lime is converted into calcium car- 

 bonate. 



A third characteristic of lime is that, being an alkali, 

 it deflocculates the clay in heavy soils. This action, 

 however, is speedily reversed: as soon as conversion 

 into bicarbonate is complete the clay is flocculated and 

 the soil changed into the desirable crumbly state. 



Effect on crop prochiction . The various improvements 

 set out above fall into two groups : semi-permanent and 

 transitory. When chalk or lime neutrahses sourness or 

 acidity, kills disease organisms or flocculates clay, it 

 produces an improvement which lasts for a long time, 

 at any rate until the undesirable condition is set up 

 again. In these cases the lime throws out of action a 

 harmful factor and raises fertility accordingly. 



The value of lime in neutralising a harmful factor is 

 well shown at Rothamsted, at Woburn and at Cockle 

 Park. At Rothamsted sulphate of ammonia is applied 

 to some of the grass every year in such quantities that 

 the soil has become acid, and consequently unsuited to 

 the growth of some of the better grasses and clovers. 

 Lime neutralises this acidity and therefore restores the 

 soil to its normal neutral condition; the effect lasts so 

 long as the soil does not again become acid. Similarly 

 at Woburn a dressing of lime counteracts the acidity, 

 and therefore the sterility, produced by excessive use of 



^ Hutchinson and MacLennan, Journ. Agric. Sci., 1914, vi. 302. 



