OVER-IRRIGATION AND ALKALI 397 



The age of the crop also determines largely the tol- 

 erance of alkali. Germinating crops can stand only small 

 quantities of alkali; but as they become older and the root- 

 system better established the tolerance increases. There- 

 fore, it is advisable to wash the alkali far down into the 

 subsoil at the time of seeding, so that germination and 

 first growth may occur without hindrance. The quality 

 of crops is often reduced by the presence of alkali. 

 Headden found that the quality of beets was largely 

 interfered with by the presence of nitrates in the soil. 



All in all, the subject of the tolerance of plants for 

 alkali is in considerable confusion. This exceedingly 

 difficult subject needs to be worked over, with new 

 experiments and devices before the last word concerning 

 it can be spoken. 



236. Cropping against alkali. Apparently the sim- 

 plest method of utilizing alkali lands is to grow upon 

 them alkali-resistant plants. Many native plants thrive 

 on alkali lands, and are relatively sure indicators of alkali 

 conditions. Greasewood, shad-scale, salt-weeds and salt- 

 bushes thrive best on lands that are fairly rich in alkali. 

 While these plants usually grow on alkali soils they often 

 do well on alkali-free soils, and are not therefore invariable 

 indicators of alkali. Unfortunately, most of the native 

 alkali-resistant plants have little agricultural value. They 

 are usually unpalatable and of low digestibility and 

 feeding value. There are a number of cultivated plants 

 that also endure alkali. Among these is the Australian 

 salt-bush, tried out in California, which yields well and 

 makes a fairly palatable forage. Sweet clover, which 

 is almost a weed hi many localities, grows remarkably 

 well on certain classes of alkali land, and, if cut early, 

 forms a palatable stock-feed. Lucern once started on 



