POOR CROPS AND HOW TO GET BETTER ONES 131 



So underdrainage is a remedy not only for excess of 

 water, but also for injury to the crop by drought. It 

 helps to make crojDsealya enables them 



to get more moisture and plant food. It is expensive, 

 but increases the crop-producing power and value of 

 the land very greatly. It makes the success of crops 

 much more certain and regular. 



Some soils are naturally underdrained. This hap- 

 pens when there is sand or gravel underlying them at 

 from three to five feet, or when the soil and subsoil are 

 both sandy. It is then not necessary to lay under- 

 drains. In the humid states sandy soils are usually 

 poor; in the arid region the sandy lands are apt to be 

 quite as rich as the clay soils (see page 34) and are there- 

 fore much valued for cultivation, being easy to work 

 at all times. ~S 



ALKALI SOILS / ^Lf f V, 



A common cause of poor crops in the arid regions 

 are the soils which, because of a light rainfall, have 

 retained in them most or all of the soluble salts which 

 have been formed from the weathering of the rocks 

 (see page 58). This is the case in many areas west 

 of the Rocky Mountains, and in the ' 'semi-arid "be 

 limg^lgjlgj^heir eastern foot. In California, Nevada, 

 Arizona, New MexFco, and northward nearly to 

 British Columbia, such " alkali lands 77 are found more 

 or less. 



