THE IERIGATION AGE. 



273 



OXYGEN 



Unites with Silicon and forms Silicic Acid. 

 Unites with Carbon and forms Carbonic Acid. 

 Unites with Sulphur and forms Sulphuric 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 metalic, 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 min- 

 eral acids attack the alkaline bases, this is what happens : 

 Silicic Acid froms 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 min- 

 eral 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 book. Moreover, their action is the 

 same as the sodas, though in a much less harmful de- 

 gree. 



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 atmos- 

 phere, but leaves the alkali salts behind to accumulate, 

 until the soil is ruined for purposes of vegetation un- 

 less they are removed, or got rid of in some way and 

 the soil thus "reclaimed," 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 simple 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 earthy 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 ap- 

 pear to be freely created by the plant itself during the 

 process of developing acetic acid, which is essential for 

 the purpose of transforming starch into sugar, whether 

 of the cane or grape variety, and for laying the founda- 

 tion of woody fiber and cellular tissues, all of which, 

 alkali tends to prevent if in excess. It is well known 

 from actual experience 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 understood the partial reclamation of 

 alkali lands, even under adverse conditions, may be at- 

 tained, 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. 



Third Alkali soils suitable for general crops. 



Fourth Alkali soils adapted only to certain special 

 classes of plants. 



The sodas are the most dangerous of the alkalis, 

 both the carbonate, or "sal soda," which is the cause 

 of "black alkali land," and the sulphate, or "Glauber 

 salts," which is the deposit on most of the "white alkali 

 lands," because they are so very easily soluble in water, 

 whereas the sulphate of lime, or "gypsum," and all the 

 other sulphates, and the phosphates, are very much less 

 soluble in water. The consequence is, the soda alkalis 

 are always shifting their location, always following the 

 water, because the latter takes them up greedily when- 

 ever they are brought in contact, whether on the sur- 

 face or in the subsoil, or under the influence of seepage 

 which carries the alkalis from a higher to a lower level. 

 The tendency of water when in motion, or flowing, is 

 first downward, it leaches, or percolates through the 

 soil, but after it has become stationary, that is, when 

 it does not find an outlet through drainage, either nat- 

 ural or artificial, it begins an upward movement toward 

 the surface through capillary action, and carries with it 

 the alkalis it contains in solution, evaporates and leaves 

 the salts on the surface. It is not difficult to under- 

 stand how the alkalis accumulate in the soil, the diffi- 

 culty begins when the attempt is made to remove them 

 and fit the soil for plant life. 



As the amount of alkali deposited in the soil in- 

 creases, the number of species or varieties of plants de- 

 creases. Where soils are charged with an excess of 

 alkalis by fortuitous or artificial means, the reader will 

 understand that the excess has been added to the natural 

 supply by the flooding or rains, or by irrigation. The 

 alkali has not been washed out of the soil by the water, 

 it has been carried into it by water charged with the 

 soluble salts, directly, or by seepage from irrigating 

 ditches. In either case, deep cultivation, surface, or 

 sub-drainage, will tend to restore the soil to its normal 

 condition. Moreover, it is not difficult to wash out of 

 the soil the elements necessary to plant life through the 

 application of water, and, inasmuch as the alkalis are 

 more soluble than any of the plant foods, it should be 



