[ .03 ] 



burying sods and exposing a new layer to the action .of 

 the elements. With the native plough scratching of the 

 soil is effected but not over-turning of the soil. With the 

 help of the mould-board the soil is overturned. Subsoiling 

 and subsoil-ploughing are done with the object of admitting 

 air and moisture into the subsoil. Subsoiling only stirs the 

 subsoil, but subsoil-ploughing brings the subsoil to the surface. 

 A subsoiler (Fig. 4) may be attached to a plough if four bullocks 



FIG. 4. THE SUBSOILER. 



are used. Surface soil is usually richer, especially in organic 

 matters, than the subsoil, and it is undesirable, as a rule, to 

 bring up the subsoil to the surface by trenching or subsoil- 

 ploughing. But it is very desirable to stir the subsoil for 

 certain crops with the object not only of admitting air and 

 moisture into it and facilitating the penetration of roots, but 

 also of breaking the impervious pan which is formed by the 

 sole of the plough. Subsoiling may be also done by a country- 

 plough being passed behind a plough fitted with mould-board, 

 the plough on the' rear stirring the soil of the furrow made by 

 the front plough in the same way as a subsoiler working 

 behind a plough does the work. Deep ploughing is also best 

 done in this country by passing one plough behind another 

 along the same groove. 



129. Another object of deep-ploughing, trenching or sub- 

 soiling is to increase the water-holding-capacity of soils. 

 Loose earth receives and stores more water than compact 



