36 



TYPES OF SOIL 



quite common on the black prairie lands. It is especially notice- 

 able in Dallas County, Texas. 



Arid Soils. In Arizona, New Mexico, Utah, Nevada, and some 

 of the other western States there is so little rainfall that the soils 



are practically unwatered and 

 are too dry for the growth of 

 ordinary vegetation. In such 

 regions only a few hardy plants 

 such as the Spanish bayonet, 

 the yucca, and various kinds 

 of cactus will grow without 

 irrigation. 



Alkali Soils are those contain- 

 ing large deposits of mineral 

 salts which check vegetable 

 growth. Alkali soils are not 

 generally encountered in humid 

 regions because the rain leaches 

 out the saline materials. These 

 soils occur in the western part 

 of the United States in the arid 

 or semiarid regions. The alkali 

 usually present is carbonate of 

 soda. When more than one 

 fourth of 1 per cent is present, 

 Giant cactus, Arizona ^ prevents germination of seed. 



It makes the soil break up in clods and the furrows do not crumble 

 to powder in drying, which is an essential feature of good tillage. 

 It may be remedied by tile draining and suitable irrigation. If we 

 have irrigation without the drainage, we only aggravate the diffi- 

 culty and increase the accumulation of saline matters at or near the 

 surface. For the water thus used carries the alkali with it, but as 

 it does not reach the natural drainage it rises again when evapora- 

 tion begins; and if all the water evaporates, the whole of the 

 alkali will come towards the surface. In parts of Argentina 

 it is said that the whole country is quickly covered with scattering 

 plants while the rains last, but as soon as the dry hot weather 

 comes, the alkali rises and kills nearly all vegetation. The ground 



