IMPROYEMEKT OF SOILS. 45 



Liming is useful laot only as adding a necessary element 

 to soils deficient in it, not only as constituting a mellow- 

 ing and ameliorating agency in respect of the texture of 

 the soil, but also as supplying an imj^ortant agency in 

 yegetable soils, and especially in clay soils, in the general 

 chemistry ©f the land on which the provision of plant 

 food depends. In marling especially, as well as in liming 

 proper, it is the calcareous element which is the most ac- 

 tive of the elements supplied. In the latter, of course, it 

 is the clay which gives the marl its characteristic texture, 

 and renders it adapted especially for the lighter and more 

 Yegetable kind of soils. The claying, which has added 

 so much to the fertility of the Fens of Cambridgeshire 

 and Lincolnshire across the water in England, owes its 

 fertilizing influence, to a considerable extent, to the lime 

 which it contains. 



Chalking", — This is a common practice on the edge of 

 chalk districts on clav soils, and wherever lime is deficient 

 in the soil, is«found beneficial, both as improving the tex- 

 ture and as adding plant food directly to the land. Some 

 of its fertilizing influence is no doubt due to the small 

 quantity of phosphoric acid which it sometimes con- 

 tains ; and its influence on the soil and its contents is of 

 the same kind as that of caustic lime, though less ener- 

 getic. 



The chalk is carried on to the field perhaps eighty to 

 hundred cubic yards per acre, set down from the carts in 

 little heaps four or five yards apart, thereafter spread and 

 left to the influences of a winter frost, which disintegrates 

 the mass and enables its moie perfect mixture with the 

 soil. 



Parins^ and Burning. — This was at one time a common 

 method of breaking up old sward in some countries of the 

 old world, but, except m a few districts, the practice has 



