SOIL MANAGEMENT. 9 



warmed, clay maintains a more uniform temperature 

 and prevents the rapid loss of heat from the soil 

 during cold weather, and late into the autumn, owing 

 to its poor conductive powers. 



Humus. The word " humus " is a general term, 

 and includes the decayed remains of animal and 

 vegetable matter of all kinds. This is the material 

 which, when mixed with sand and clay, gives richness 

 and fertility to the soil, and as decay proceeds the 

 valuable ingredients it contains are liberated for the 

 benefit of the crops. Humus also has the power of 

 absorbing and retaining moisture and heat in a 

 wonderful degree ; it improves the texture of a soil, 

 rendering it more friable and easy to work, and is the 

 medium in which there lives an immense number of 

 minute organisms so essential to the production of 

 available plant foods. 



Lime. This is essentially a transitory substance 

 constantly being removed by crops and percolating 

 water, and absorbed by combination with acids from 

 decaying vegetable matter, fertilisers, etc. Period- 

 ical dressings of lime are very necessary, but this will 

 be fully discussed in the chapter on manuring. 



Soils may be simply classified as a clay soil when 

 this material predominates to any great extent ; a 

 sandy soil when sand is present in excess ; a black 

 organic soil when it contains an excessive amount of 

 humus, as all peaty soils do, and sometimes, though 

 to a less degree, old garden soils which have long been 

 heavily manured ; and as a loamy soil. Loam is the 

 best kind of soil, being very fertile, easy to manage, 

 and well adapted for the successful cultivation of 

 vegetable crops. Loams vary somewhat in texture, 



