220 EGYPTIAN AGRICULTURE. 



porous. For the improvement of light sandy soils, no 

 better system is known than that of growing berseem, 

 which not only greatly enriches them in nitrogen in 

 which they are generally deficient, but also by the addi- 

 tion of vegetable matter renders them more absorptive 

 and retentive and greatly enhances their value. In Egypt 

 there is a great want of organic matter, and were it not 

 for the system of indirect green manuring practised by 

 the ploughing in of berseem, it is difficult to see how the 

 fertility of our soils could have been maintained. 



Some soils give up their water to plants much more 

 readily than others. In a clay soil, for example, holding 

 a considerable amount of water, plants cannot draw upon 

 it to such an extent as when growing on land whose 

 retentive power is less. Plants may wilt in clay contain - 

 ing 6 or 8 per cent, of water, whereas they will grow in a 

 less retentive soil although the percentage of water be 

 less. 



Closely connected with the absorption and retention of 

 water is the question of temperature. Though the tem- 

 perature of the surrounding atmosphere largely influences 

 the growth of the plant, yet it is affected to a very con- 

 siderable extent by the temperature of the soil, and the 

 warmer the land is, generally speaking, the more rapid 

 will be the development of the plant. Soils of a sandy 

 nature which hold but little water attain the highest 

 temperature, and plants therefore mature more quickly 

 on them than on those of a more retentive nature. 



Another point to which reference may be made is the 

 power of the soil to absorb gases. The presence of air 



