The Science of the Soil 



105 



of iron. This is distinctly unfavourable to plant growth, and is often 

 met with in yellow clay soil; but, as already stated at p. 97, it would 

 be foolish to choose a soil of this nature in the first place. This poisonous 

 ferrous oxide must not be confused with ferric oxide or peroxide of iron, 

 which is a valuable constituent of the soil. It promotes vegetation and 

 the development of the green colouring matter in leaves, and performs 

 other useful functions. 



Even if one is so unfortunate as to have a soil containing much poison- 

 ous ferrous oxide, the best way to remedy this defect is by bringing up 

 the bottom soil and exposing it to the action of the weather. One of the 

 most important changes that takes place is the absorption of oxygen from 

 the air by the ferrous oxide, 



W n > 1 I 



which in the course of time be- 

 comes converted into the useful 

 and fertilizing ferric oxide. 



The cost of trenching soil to 

 a depth of 3 ft. will vary from 

 8 to 12 per acre, an appalling 

 item apparently to a man with 

 limited capital; and then manur- 

 ing, hoeing, &c., must be added, 

 so that the cost of deep cultiva- 

 tion may well average 9 or 10 

 per annum per acre if vegetable 

 crops only are to be grown. 

 Against this great expense, how- 

 ever, must be placed the follow- 

 ing advantages: (1) An abundance of available plant food; (2) earlier, 

 heavier, and more remunerative crops; (3) abundance of warmth and 

 moisture at the roots in the hottest of summers; (4) lack of insect pests 

 and fungoid diseases; (5) saving in insecticides and fungicides; and (6) an 

 absence of weedy vegetation and a consequent saving in plant food. 



If it is intended to grow fruit trees and bushes, it would be even more 

 wise to trench the soil to a good depth at first before planting, because 

 once fruit trees are planted it will be afterwards almost impossible to 

 rectify any troubles in the soil without incurring great expense. To bring 

 soil into a proper condition for fruit culture, it may be advisable to crop 

 it with Potatoes, Cabbage crops, Jerusalem Artichokes, Celery, Parsnips, 

 &c., the roots of which would penetrate the soil deeply and break it into 

 finer particles. 



When digging, double digging, or trenching, it will be found convenient 

 to divide the ground into convenient portions, as shown at a, b, c, d (fig. 87). 

 By dividing each portion, as shown at ef. into two sections, a good deal 

 of labour and wheeling will be saved. The soil from the first trench, 

 6 to /, when taken out, may be placed in front of the section efcd at fd 

 When the work has reached ae, the trench there is to be filled with soil 



Fig. 87. Diagram showing how the Ground may be 

 marked out for Digging or Trenching 



