On Subsoil-Ploughing, 



31 



above, there is reason to suppose that this maximum point lies 

 between 24 and 43 per cent. ; every experiment, therefore, made 

 on soil containing more than the one and less than the other, 

 reduces the doubtful soils within narrower limits. It would also 

 be advisable to try the effect of subsoiling on two soils containing 

 equal quantities of alumina, but otherwise differing in their com- 

 position, as it is possible that other substances, in combination 

 with alumina^ may in some degree affect the result. 



I have thus far confined myself to stiff soils ; but as the subsoil- 

 plough has been little used on light land, and its effect therefore 

 is little known, the following paper from Mr. Denison, of Kiln- 

 wick Percy, will be read with great interest. 



" That much good is effected upon strong land by draining 

 and subsoil-ploughing is a fact that is generally considered to be 

 incontrovertible : but few have been hitherto met with who would 

 not ridicule the idea of applying the same operation to light 

 blow-away sand : and as it is to this latter description of land that 

 I have chiefly turned my attention and experiments, I will confine 

 myself to what I really know and have experienced. 



In the year 1837 I purchased a considerable tract of sandy 

 land, and I will now mention the mode by which it was brought 

 into cultivation ; and I feel so thoroughly grateful to the subsoil- 

 plough for the share it has had in my success, that I cannot do 

 sufficient justice to it without fully explaining the system upon 

 which I worked; — and then I will leave it to my readers to judge 

 whether I can say too much in its praise. 



'^''The tract of land upon which I began was in extent about 

 400 acres, the principal part of which w^as rabbit-warren. The 

 general character of this tract was, that, although upon the whole 

 it was nearly a level, yet the surface was undulating ; the sandy 

 swells being covered mth heather, and the hollows a bed of 

 aquatic plants, being for many months in winter entirely covered 

 with water. Of the sandy hills, the soil, as far as I am able to 

 judge, was a sterile, impalpable sand, having been heretofore cul- 

 tivated, and again abandoned. About 6 or 8 inches below the 

 surface this sandy soil seemed to become hardened into almost a 

 sandstone, with the occurrence occasionally of an impervious bed 

 of ironstone ; presenting, Avherever it did occur, a complete obsta- 

 cle to the entrance of the ploughshare : generally speaking, how- 

 ever, these nodules, or beds of ironstone, lay at a depth somewhat 

 below the ordinary ploughings. The marshy hollows were of a 

 totally different nature, and their cultivation had never been at- 

 tempted; an idea apparently having prevailed that they were 

 below the reach of drainage. When become dry, the soil of these 



