2G CHAPTER III 



horizontal. By so doing a mat of vegetation does not separate 

 the soil from the sub-soil, consequently soil moisture and air 

 move to better advantage, and in subsequent operations the 

 organic matter is better distributed throughout the soil. A 

 drag chain is of service in ploughing under ground heavily 

 covered with vegetation, and a coulter lessens the draft and 

 gives a clear cleavage. Harrowing, if required, should always 

 follow ploughing almost immediately, because the soil is not so 

 liable to form clods as when a period of a day or two or even 

 a few hours is allowed to elapse. 



The Sub-Soil Plough " consists essentially of a small 

 mole-like point on a long shin. It is drawn through the 

 bottom of the furrow and loosens the sub-soil to a depth of 18 

 inches to 2 feet without mixing the sub-soil with the soil." 

 Its use in South Africa has never been popular. It is apt to 

 loosen the soil to such an extent that excessive drying-out will 

 take place. Moreover, since the condition of the sub-soil can- 

 not be readily seen, if of a clayey nature, it may be badly 

 puddled by sub-soiling. 



The Lister Plough is a double mouldboard plough, used in 

 the drier parts for planting maize and sorghum in the furrow. 

 It leaves the ground in ridges which, by subsequent cultivation, 

 are spread over the roots of the plants. It is used chiefly in 

 sandy soils, and is supposed, by promoting lower root growth, 

 to enable plants to withstand drought. 



Cultivators. — These implements are to-day extraordinarily 

 varied in design. They are used chiefly for destroying weeds, 

 reducing clods and for bringing the soil into a good condition 

 for seeding purposes. Wheeled cultivators are fast coming into 

 general use and have maxiy advantages over other types, 

 e.g., the depth of cultivation can be better regulated, the man 

 operating them is less fatigued, and they are easier to 

 manipulate. 



The spike-tooth, smoothing, spring-tooth and disc harrows 

 and weedcrs arc used to level the ground as well as to loosen 

 and pulverise the surface of the soil. The spike-tooth is used 

 for shallow cultivation, the spring-tooth for deeper cultivation 

 and the disc harrow often takes the place of the plough in 

 deep soils. Weeders are modified spring-tooth harrows, having 

 numerous long, narrow prongs, used principally for killing 

 weeds while in the seedling stage. Harrows are also used for 

 covering broadcasted seed. The use of cultivators must be 

 regulated according to the stage of development of the crop. 



