ix.] PARING AND BURNING 303 



the texture ; in the charred clay also, some of the potash 

 was rendered more available, while the plant residues 

 provided mineral salts and alkalis to promote nitrifica- 

 tion. The drawback to the process is the inevitable 

 loss of nitrogen to the soil ; but any one who has 

 noticed how freely crops grow on the patches of 

 arable land where couch heaps have been burnt the 

 season before will see that, for the time being, the 

 fertility of the soil is increased by the process. Other 

 advantages of burning lie in the destruction of weeds 

 and insect life of all kinds, and although it has been 

 almost wholly discontinued at the present day, the 

 older writers on agriculture are unanimous as to its 

 beneficial effects in bringing poor clay land into 

 cultivation. The destruction of the protozoa and the 

 subsequent burst of activity on the part of the organisms 

 producing plant food, to which reference has already 

 been made (p. 232), is also doubtless a factor in the 

 result. 



A variation on the old process of " clod burning" 

 consists in " border burning," in which clay is dug from 

 one corner of the field and burnt by means of the couch 

 and other weeds cleaned off the land, the hedge trim- 

 mings, etc. ; the burnt clay is then spread over the 

 surface to improve the texture of the soil. Without 

 doubt the latter process might still be profitably adopted 

 where heavy clay land is under the plough ; if every 

 year some clay were added to the fires made from the 

 weeds and hedge trimmings, valuable material for 

 lightening the soil would be obtained without wasting 

 too much soil nitrogen. 



Of course the incorporation of any large-grained 

 material will improve the texture of clay soils ; in some 

 cases sand has been dug and spread with advantage ; 

 road scrapings, town refuse, and even coal ashes help 



