THE IREIQATION AGE. 



207 



Notes on Practical 

 Irrigation 



D. II. Anderson 



ALKALI SOILS. 

 Their Nature, Treatment, and Reclamation. 



The "alkalis," as they are called, are common to all 

 soil?i wherever they may be found on the globe; they 

 belong to earth and are part of its essential constituents. 



Originally, they were brought or carried into the 

 soil along with the other elements which form its in- 

 organic bulk (as has been explained in Chapter II), by 

 the pulverization of rocks and minerals, the deposition 

 of inorganic sediment held in solution by water, by 

 glacial action, by seepage from rivers, and numerous 

 other ways. 



These elemtns, if unacted upon, would forever re- 

 main in an insoluble, inert condition, incapable of ex- 

 erting any influence upon each other, or of performing 

 any functions whatever; in which case, however, there 

 could not be any plant life of any kind. But nature 

 comes in and begins action upon these elements and 

 changes their form so that they may become capable 

 of aiding in the production of plants by furnishing them 

 with the food to make them grow and ripen their fruit 

 or seed. 



First, we have the atmosphere, or air, which, how- 

 ever arid the region, contains oxygen in a very large 

 proportion, and this oxygen attacks the inorganic ele- 

 ments, transforming them into various substances, or 

 rather fits them to be acted upon by other substances so 

 that they may become useful or otherwise. Thus, oxy- 

 gen acts upon potash, soda, lime and magnesia to form 

 what are known as "alkaline bases/' that is, the founda- 

 tions for the "salts," which are beneficial in moderate 

 quantities but injurious in excess. The forces of nature 

 are always at work, regardless of the quantity of the 

 product; certain laws are followed, and these laws keep 

 on operating in certain unvarying ways, according to a 

 fixed program, which is never changed unless man comes 

 in and compels a change. The following table will en- 

 able the reader to understand in a general way how 

 nature works upon the elements in the soil through oxy- 

 gen: 



Oxygen. 



Unites with Potassium and forms Potash. 



Unites with Sodium and forms Soda. 



Unites with Calcium and forms Lime. 



Unites with Magnesium and forms Magnesia. 



The oxygen acts upon the above four metals just 

 it does on iron exposed to the air, when it forms the 

 familiarly known "rust," which is technically called 

 "oxide of iron." So the potash, soda, lime and mag- 

 nesia are really the earth oxides, the four of them being 

 "alkaline bases," that is, the foundations upon which to 

 compound all the various kinds of alkalis. 



These "oxides," or "bases," in themselves, would be 

 of very little use or harm while in that state, but the 

 oxygen in the air and everywhere else attacks the other 

 ssential elements in the soil as well as the potash, soda, 

 lime and magnesia, that is, the silicon, carbon, sulphur 

 and phosphorus, but instead of converting them into 

 oxides, or alkaline bases, turns them into "acids." The 

 following table will explain: 

 Jnites with Silicon and forms Silicic Acid. 

 Jnites with Carbon and forms Carbonic Acid. 

 Jnites with Sulphur and forms Sulnhuric Acid. 

 Unites with Phosphorus and forms Phosphoric Acid. 



Here is where the whole trouble about alkali soils 

 begins, for these acids mentioned in the last table, which 

 may be called mineral, or metallic, acids, have a great 

 affinity for the alkaline bases mentioned in the first table, 

 and greedily seize upon them, forming "salts," as they 



are commonly called. When these mineral acids attack 



the alkaline bases, this is what happens: 



Silicic Acid forms Silicate of Potash, Soda, Lime and 



Magnesia. 

 Carbonic Acid forms Carbonate of Potash, Soda, Lime 



and Magnesia. 

 Sulphuric Acid forms Sulphate of Potash, Soda, Lime 



and Magnesia. 

 Phosphoric Acid forms Phosphate of Potash, Soda, Lime 



and Magnesia. 



It is the carbonate of soda, or what is commonly 

 called "sal soda," which makes "black alkali land," and 

 sulphate of soda, or "Glauber salt," which constitutes 

 "white alkali land." There are numerous other salts 

 formed by combining the alkaline bases and the mineral 

 acids, but sufficient are given here to make the principle 

 clear; to enumerate the others would require a volume, 

 and complicate too much the idea sought to be conveyed 

 in this work. Moreover their action is the same as the. 

 sodas, though in a much less harmful degree. 



So far, water has been kept in the background, as 

 unnecessary to the formation of these salts, but when 

 water is brought in the distribution of these alkaline 

 salts is largely aided, for the alkalis are extremely soluble 

 in water, the latter taking up nearly its own weight of 

 the salts. When this happens, the alkalis are carried 

 wherever the water penetrates, and when it comes to 

 the surface it evaporates into the atmosphere, but leaves 

 the alkali salts behind to accumulate, until the soil is 

 ruined for purposes of vegetation unless they are re- 

 moved, or got rid of in some way and the soil thus "re- 

 claimed," as it is called. 



In this inorganic matter, plant life is impossible. 

 As has already been said, organic matter in combination 

 with the inorganic matter, is essential to plants of any 

 kind, and here originates a phenomenon as common as 

 the continual process of the formation of alkalis by 

 combinations with the mineral, or metallic acids, as above 

 specified. Organic matter also combines to form acids 

 which are called "vegetable acids," and they also readily 

 combine with the alkaline bases, the result of which is 

 mutual destruction. This will be understood from a 

 single experiment that any reader can try. 



Vinegar is the most commonly known vegetable acid, 

 the technical name of which is "acetic acid," it being 

 formed during the germination of seeds in the ground, 

 as will be explained in the chapter on Plant Foods. The 

 plant forms it within its tissues and then rejects it for 

 the purpose of permitting it to continue dissolving the 

 earthly substances with which it is in contact. It is also 

 formed artificially for domestic use. Now this vinegar 

 is the natural enemy of the alkalis. When poured upon 

 any of the alkalis of potash, soda, or magnesia, it causes 

 a hissing or effervescence. When this ceases, there is 

 left neither an alkali nor acid, both have disappeared, and 

 their substances are totally changed into something else 

 a new salt called an "acetate," which is neither one thing 

 or the other; they have mutually destroyed each other. 



These acetates are not noxious to plants, and appear 

 to be freely created by the plant itself during the process 

 of developing acetic acid, which is essential for the pur- 

 pose of transforming starch into sugar, whether of the 

 cane or grape variety, and for laying the foundation of 

 woody fiber and cellular tissues, all of which, alkali tends 

 to prevent if in excess. It is well known from actual ex- 

 perience that sugar bearing plants, such as sorghum, 

 sugar beets and trees of abundant starch and woody fiber 

 will flourish luxuriantly in alkali soils that will not even 

 permit the germination of cereals, or alfalfa. The reason 

 why this is so is not far to seek, and when well under- 

 stood the partial reclamation of alkali lands, even under 

 adverse conditions, may be attained, and wholly so where 

 the conditions are opposed to the accumulations of alkali 

 from artificial sources. 



Dangerous Percentage of Alkali. 



There is much controversy about the dangerous 

 amount of alkalis in arable soils, but the entire ques- 

 tion may be resolved into four divisions: 



First Soils naturally so heavily charged with alkali 

 as to be worthless. 



Second Soils in which the alkali is increased by 

 fortuitous or artificial means. 



