SOIL MANAGEMENT. 



25 



extent. As a rule they possess sufficient tenacity to give the 

 necessary stability without being unduly heavy. They are 

 highly retentive of moisture, yet sufficiently coarse to allow 

 free movement of water, and consequently form some of the 

 best soils for resisting drought. They are well supplied with 

 plant-food, are suited to a wide range of crops and are gener- 

 ally highly productive. 



In some cases the quantity of fine silt present is so large 

 that the soil is very intractable, closely resembling clay. 

 Liberal incorporation of organic matter will most efficiently 

 remedy this condition. 



Implements and Their Uses. — According to their effect 

 on the soil implements may be divided roughly into two 

 groups: (1) those that loosen the soil, e.g., ploughs, and (2) 

 those that compact the soil, e.g., rollers. 



Ploughs. — " The primary function of a plough is to take 

 up a ribbon of soil , twist it upon itself and lay it down bottom 

 side up or partially so. In the process tw^o things result : (1) 

 If the soil is in " proper condition for ploughing it will be 

 shattered and broken up. The furrow slice is sheared or split 

 into many thin layers both vertically and horizontally, result- 

 ing in the complete pulverisation of the soil ; (2) the soil is 

 partially inverted and any rubbish is put beneath the surface.'' 



The degree to which ploughs will pulverise the soil is 

 dependent on the condition of the soil, the type of plough and 

 the rate at which it is drawn along. 



Ploughs are of two general types : the mouldboard and the 

 disc. The latter has a lighter draft for the same amount of 

 work done because of its rolling friction as opposed to the 

 sliding friction of the former. While not suited to sod or 

 stoney land, the disc plough is especially effective on very dry, 

 hard soil, and for turning in and covering rubbish. 



The mouldboard ploughs have more varied shapes and 

 consequently more varied uses than the disc ploughs. For 

 general purposes those having a decided overhang are the most 

 useful, because they have a marked pulverising action. On the 

 other hand, those with a long sloping mouldboard are more 

 adapted to ploughing sod land, beca.use the furrow slice is well 

 packed against its neighbour without being broken. 



Besides taking the precaution to plough only when the 

 soil is in a suitable condition, some other considerations should 

 also he observed. The furrow slice should not be completely 

 inverted but should be at an appreciable angle with the 



