CHAPTER XV 



COMPARISON OF FOREST VALUES WITH AGRI- 

 CULTURAL VALUES 



225. Agricultural Soils. Agricultural soils are soils which 

 will produce agricultural crops continuously in paying quan- 

 tities, under proper cultivation and treatment. Many classes 

 of soils will produce scant crops for short periods, after which 

 they must be abandoned. Such soils should seldom be used 

 for crops at all but kept under forest cover. Permanent agri- 

 cultural fitness of soil is determined by six factors: quality of 

 the soil itself, topography or slope, climate, water supply, the 

 personal or human factor, and the economic factors. 



226. Quality of Soil. Soils to be agricultural must be free 

 from excessive quantities of rock, and not too sandy, since 

 loose-textured soils will not retain sufficient moisture or soluble 

 plant food to permit satisfactory growth. They should be 

 underlaid by a permeable subsoil which permits sufficient drain- 

 age. Deep sands, and stiff clay underlaid by hard-pan, are 

 familiar types of non-agricultural lands. 



227. Slope. The slope is important, since crops must be 

 cultivated, and upon steep slopes, if not terraced, the loosened 

 surface washes away, deep gullies are formed and the land is 

 permanently ruined for agriculture. Slopes varying from 10 to 

 20 per cent, according to rainfall and quality of soil, will prevent 

 permanent cultivation. 



228. Climate. Crops will grow in all but the coldest climates 

 if given sufficient water. But in mountainous regions, lands 

 at high elevations resemble regions near the arctic circle. Frosts 

 occur every month in the year, and the growing of all agricul- 

 tural crops, except a poor quality of hay, is prevented. Such 

 lands are non-agricultural, regardless of the quality of soil. 



226 



