ALKALI. 



DEFINITION AND METHODS OF TREATING IT. 

 BY E. M. SKEATS, OF NEW MEXICO. 



WHAT is alkali ? Webster' s dictionary 

 says " a salifiable base, having in a 

 greater or less degree a peculiar acrid 

 taste, the power of changing blue vege- 

 table colors to green and the color of 

 turmeric and rhubarb to brown. Potash, 

 soda and ammonia are the leading 

 alkalies." That is more or less the 

 answer a chemist would give to the 

 question, but since irrigation has become 

 a popular science the definition requires 

 enlarging. To an irrigationist alkali has 

 come to mean any efflorescence which may 

 form on the surface of the ground. The 

 irrigationist divides this alkali into two 

 classes, one he calls "black alkali" which 

 is very harmful to vegetation, the other 

 he styles "white alkali" and he con- 

 siders it moderately harmless. 



The "black alkali" consists in great 

 part of the carbonates of potash or soda; 

 these have great solvent power on vege- 

 table matter, turning it black and killing 

 live plants in contact with it. It is de- 

 cidedly dangerous and is a true alkali. 



But with regard to "white alkali" the 

 name is misleading as very frequently the 

 white efflorescence contains no alkali at 

 all, according to Webster's definition, but 

 may consist of any salt which is soluble 

 in water; it may be a valuable plant food, 

 or it may be a poison, or it may have no 

 effect at all on plant growth. It consists 

 almost always of the mineral matters in 

 solution in the bottom water. According 

 to the nature of this water (the shallow 

 well water of the neighborhood) so does 

 the nature of the " alkali" vary. 



I believe it is a popular idea that 

 "alkali" comes from the soil. Indirectly 

 of course, it does; but not necessarily or 

 generally from the local soil but from soil 

 through which the bottom water has flowed. 

 In very few cases will you have any alkali 

 at all on the surface unless you have a 

 bottom water within eight feet, and the 

 alkali will consist simply of the solids of 

 this water. 



Soil is porous and like a wick and, ac- 

 cording to whether it is fine or coarse, it 

 will draw up water to a greater or less 

 height. A very sandy soil will draw it up 



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about one and a half to two feet, while an 

 adobe will draw it up four or five feet. 



Suppose you have, then, an adobe soil 

 and your well shows water within four 

 feet of the surface, and the water contains 

 a large proportion (not necessarily a large 

 amount) of carbonate of soda, you will 

 have " black alkali " in your ground and 

 will have to be very careful how you treat 

 it. This is the case in a few parts of 

 California, in parts of India, and in many 

 parts of South America. 



Now, suppose that below you is a dis- 

 trict of gypsum beds and that your bot- 

 tom water flows through these. It dis- 

 solves some of the gypsum or sulphate of 

 lime, the sulphate of lime and carbonate 

 of soda in the water change and form car- 

 bonate of lime and sulphate of soda. Your 

 friend who, perhaps, has property below 

 these gypsum beds, does not find the same 

 difficulty with his garden that you do. 

 His well perhaps shows the water but two 

 feet from the surface, but the efflorescence 

 on his ground consists of carbonate of 

 lime and sulphate of soda, both of which 

 salts are harmless. 



Take another example: Your land is in 

 the Pecos valley a gypsum formation 

 your well shows the water seven feet from 

 the surface. The water contains sulphate 

 of lime and magnesia and some common 

 salt. 



Through the dry season you have no 

 alkali or efflorescence on the surface, as 

 the soil cannot draw the water seven feet. 

 But a rain comes, or you irrigate, and the 

 soil is wetted down to where it can draw 

 the bottom water. The water from above 

 mixes with that from below and dissolves 

 much of the lime, magnesia and salt which 

 the latter has left two or three feet below 

 the surface. This is now drawn farther 

 up and appears on the surface after the 

 sun has dried it. It is thus that an 

 efflorescence can appear when the bottom 

 water is as much as eight feet from the 

 surface, though the soil can only draw it 

 a little more than four feet. 



In this instance the efflorescence con- 

 sists of sulphate of lime and magnesia 

 and common salt with no true alkali, and 



