SOIL MANAGEMENT. 23 



(i) Silts — more than 75 per cent, silt and a small amount 

 of sand, but very little clay. 



The name in every case indicates the fraction whose pro- 

 perties dominate in the soil, except in the case of loams, 

 where the properties of no one fraction dominate. 



It is understood, of course, that all normal soils contain a 

 small amount of organic matter, and frequently also a small 

 amount of free carbonate of lime. When present in relatively 

 large quantities these substances modify the soil structure to 

 sucli an extent that the above classification is of little or no 

 value, and the soil is given a class name which indicates the 

 dominance of OT-ganic matter or lime, as the case may be. 



Tillage, Treatment and Characteristics of Various 

 .Soils. — (1) Coarse Sands. — These are quite useless for general 

 farm crops and will, therefore, not be discussed. 



(2) Sandy Soils. — Their cohesiveness is low, consequently 

 they are light (easily worked) and in extreme cases show a 

 tendency to blow. They are generally poor in plant food and 

 leach readily, especially if the particles arc large. Their reten- 

 tive power for moisture is low, but the movement of soil 

 moisture is rapid. Consequently, they are apt to dry out 

 quickly and very soon suffer from drought. Irrigations must 

 be more frequent than on the heavier types of soil. Sandy 

 soils are usually poor for general farming crops, but since they 

 warm up rapidly they are eminently suitable for vegetable- 

 growing. Moreover, in the intensive cultivation practised by 

 the vegetable-grower, heavier applications of manures are 

 employed than can be afforded by the ordinary farmer. The 

 former finds it profitable to maintain and to increase the 

 fertility of a sandy soil, while the latter may find it un- 

 economical. 



Organic matter is required to give body to these soils and 

 increase their moisture retention. Consequently, their treat- 

 ment should include a rotation having a leguminous green- 

 manure. Stable or kraal manure is particularly valuable for 

 these soils. 



The character of the sub-soil must not be overlooked, since 

 a sandy soil resting on a more impervious sub-soil may be a 

 very good soil for general farming. On the poorer types sweet 

 potatoes and rye are the most successful crops. 



(3) Sandy Loams. — These possess the same character- 

 istics as sandy soils, but in a less marked degree. They 

 are more retentive of moisture and plant-food, fairly easy to 



