FOREST IN RELATION TO AGRICULTURE 489 



another way of clearly proving the beneficial effect of the forest, or 

 ameliorating the condition and plant-food content of the soil. On the 

 comparatively worn-out and poor soil near Ibadan a firewood planta- 

 tion was started some years ago ; now already, in the shade of 

 the Ayin, Anogeissus leiocarpus and Cassia Siamea trees, the fallen 

 leaves have decayed and formed a layer of humus, killing out the 

 lalang grass at the same time. Needless to say, it is a very expensive 

 method to wait until the forest has been destroyed, the soil impover- 

 ished, and trees again planted, before an improvement in the soil 

 conditions can be expected. 



5. Individual trees, and thus trees in the aggregate, viz. forests, 

 take less mineral matter out of the soil than agricultural crops covering 

 a similar area. It has been calculated that the trees on an acre of 

 land only take one-twelfth of the amount of mineral matter out of 

 the ground which is requii'ed by an agricultural crop on the same area. 

 It follows from this that trees, and in the same way forests, may be 

 left standing upon or be grown on land which is nearly or absolutely 

 worthless from an agricultural point of view. In the more civilized 

 countries this is seen, for instance, in the way in which the mountain 

 ranges of Germany have remained covered with forest and the sandy 

 Landes district of France has been planted with forests of pine. 

 In Canada, the Spruce Hills Reserve, near the Canadian Pacific Railway 

 in Manitoba, is another example of the setting aside of poor, almost 

 worthless agricultural land as a permanent forest area. In Nigeria, 

 the Oban Forest Reserve and the forest-covered hills of Olokemeji 

 are further examples of the practice of this principle. 



Generally speaking, in fact, in most civilized countries there are 

 really three types of land, viz. : 



(a) Absolute farm-land, which comprises the very richest and best 

 land of the country, in which forests should only be allowed to 

 stand, as an exception. 



(6) Relative forest-land, comprising land which can be used 

 permanently for agriculture, but requiring a great deal to be spent 

 on improvements or manures to make it suitable for the purposes, 

 but which in its natural state carries a heavy stand of timber, could 

 be used for forests indefinitely. 



(c) Absolute forest-land, comprising land which, owing either to 

 its elevation, aspect, soil or position, cannot be used for the permanent 

 cultivation, or in some cases even the temporary cultivation, of 

 crops. 



6. The forest protects agricultural land against storms and insect 

 pests. In many places, owing to very strong winds, certain crops 

 cannot be grown. For instance, it is said bananas cannot be grown 

 at Zaria owing to the prevalent strong winds. In the Chang district 

 of the Cameroons the natives only plant plantains near their houses 



