LIME DOES >-0T BENEFIT EXHAUSTED LANDS. 395 



judicious admixture of all This truth is confirmed by the practical 

 observation, that on soils so exhausted farm yard manure along with 

 the lime does not produce the same good results as in other cases. All 

 that the soil requires is not supplied in sufficient abundance by these 

 two substances laid on alone. 



7°. On lands of this kind, and on all in which vegetable matter is 

 wanting, lime may even do harm to the immediate crop. It is apt to 

 singe or burn the corn sown upon them (Brown) — an effect which is 

 probably chemical, but which may in part be owing to its rendering 

 more open and friable soils already, by long arable culture, too open. 

 (Morton.) 



8°. A consideration of the circumstances above adverted to explains 

 why, in some districts, and even in some whole provinces, the use of 

 lime .in any form should be condemned and even entirely given up. 

 The soil has been impoverished through its unskilful application — or, 

 by large admixtures of lime or marl for a series of years, the soil has 

 been so changed as to yield no adequate return for new additions. Thus 

 for a generation or two the practices of liming and marling are abandoned, 

 to be slowly and reluctantly resumed again, when natural causes have 

 removed the lime from the soil, and produced an accumulation of those 

 other substances which, when associated with it, contribute to the pro- 

 ductiveness of the land. 



§ 17. Effects of an overdose of lime. 



There are several effects which are familiar to the practical man as 

 more or less observable when lime in any form is laid too lavislily upon 

 the land. Thus 



1°. It is rendered so loose by an overdose as to be capable of hold- 

 ing no water (Karnes). Upon stiff* clays a very large quantity indeed 

 will be required to produce this effect. 



2°. By an overdose of quick-lime the land is hardened to such a degree 

 as to be impervious to water or to the roots of plants. Several parts of 

 the (/arse of Gowrie are thus rendered so hard as to be unfit for vegeta- 

 tion — (Lord Karnes' Gentleman Farmer, edit. 1802). This effect will 

 be observed only in soils which are naturally wet and undrained, or 

 where much rain has fallen and lingered on the land after the lime 

 has been applied (p. 388). 



3°. But the most injurious effect of an over-liming, whether it be 

 laid on at one or at successive periods, is the exhaustion by which it is 

 succeeded. " An overdose of shell-marl," says Lord Kames, "laid per- 

 haps an inch thick, produces for a time large crops, but at last renders 

 the soil capable of bearing neither corn nor grass, of which there are 

 many examples in Scotland." The same is true of lime in any form. 

 The increased fertility continues as long as there remains an adequate 

 supply of organic (animal and vegetable) matter in the soil, but as that 

 disappears the crops every year diminish both in quantity and in quality. 



An interesting illustration of this exhausting power of lime is afforded 



by the observed effects of long-continued marling upon certain poor soils 



in the province of Isere, in France. The marl there emplo3'ed is a 



•audy marl, containing from 30 to 60 per cent, of carbonate of lime — • 



17* 



