PREPARING THE PLANTING AREA 81 



land, the drains would soon become choked with roots, 

 unless they were too deep down, when they would be 

 useless to drain the land. So recourse is had to open 

 drains or ditches. 



x\ large percentage of the land given up to forestry 

 operations is too heavy and waterlogged to grow farm 

 crops. This condition may arise from different causes. 

 There may be a layer of moorpan or the subsoil may be 

 impervious to water, the mineral soil may be covered 

 with a layer of peat varying in depth, or the area may be 

 affected by flood water from a river or by springs. 



In the first two cases the use of subsoil ploughs may 

 remedy the fault, and no further draining may be 

 necessary. 



The first thing in draining is to find a convenient outlet 

 for the main drain in some existing watercourse. From 

 this point the line of the main drain should be marked 

 out, following the lowest ground on the area. If this is 

 not easily discernible to the naked eye, a spirit-level must 

 be used. 



Very accurate work in levelling is not perhaps so neces- 

 sary with open drains as it is with field drains, but never- 

 theless it should be carefully done. The levelling instru- 

 ment, which is fixed upon a stand and made level by 

 means of screws, is set up midway between two points 

 A and B on the line to be levelled, the distance between 

 these points being measured and a peg driven in flush 

 with the ground at each point, and the instrument correctly 

 set by means of the levelling screws. A staff marked in 

 feet, tenths and hundredths of a foot is held perfectly 



6 



