WATER SOILS. 455 



I 



appear in the stored waters are large. ' ' The amount of potash present is not large 

 and comes mainly from seepage water or other sources besides the river water. 



"The amount of nitrogen, including all forms, added with the irrigation water, 

 being less than 4 lbs. per acre, is negligible. . . . 



"Water used in direct irrigation, that is, water conveyed by means of ditches 

 directly from the river to the land irrigated, suffers less change than when stored, 

 but <loes not by any means escape altogether." 



Observations on the changes which water undergoes when used in irrigation "indi- 

 cated that water flowing for 600 ft. over the plat experimented with, carried between 

 800 and 1,000 lbs. more salts in solution per acre-foot than the on-flowing water. 

 The first water that flowed off gave much higher results, but subsequent samples 

 showed a rapid falling off. The water entering the soil caused the solution of not 

 less than 4,400 lbs. of salts per acre-foot, and probably very nearly three times this 

 amount. 



"The salts taken into solution by the water entering the soil and becoming ground 

 water, are calcium, magnesium, and sodium sulphates. The salts dissolved in the 

 next largest quantities were sodium chlorid and sodium carV)onate. The amount of 

 salts brought into solution in the ground water, due to the application of water to 

 the stirface, varies not only in the total amount of salts, but also in the relative 

 quantities of the individual salts. The salt that went into solution the most freely 

 in 1898 . . . was sodium sulphate, for which we found an increase of 1,430 lbs. in 

 each acre-foot of ground water. In 1899, the largest increase was shown by calcium 

 sulphate, an increase of 1,6^58 lbs. per acre-foot." 



Some of the conditions which probably cause the variations in the relative solu- 

 bility of the different salts are discussed. These include character and amount of 

 water applied, character of soil, and temjierature and other climatic conditions. The 

 general conclusion is reached "that the salts in tlie ground water are essentially the 

 same at all times, and the application of water to the surface, whether it be irrigation 

 water or rainfall, does not change in an}' material way the salts jiresent. The rela- 

 tive quantities in which they are held in solution in the ground water vary quite 

 widely, while the causes of the variations are not evident." 



The results obtained in a study of the relation between the composition of the 

 ground water and drainage water, although not strictly comparable since the sam- 

 ples were not obtained from the same plats, lead to the conclusion that the drain 

 waters at all times differ from the ground water. "They contain a smaller quantity 

 of salts in s(jlution, and are more uniform in this content than the ground waters. 

 The salts present stand in a different order, especially in regard to their relative 

 ciuantities, sodium sulphate sometimes disappearing entirely. Calcium sulphate 

 is uniformly first in quantity, magnesium second, sodium carbonate third, and sodium 

 chlorid fourth, with sodium sulphate quite irregular, but usually less than the sodium 

 chlorid. The first significance of these facts is that our drains benefit our lands 

 by removing the surplus water, rather than the useless or deleterious salts, from the 

 soils. . . . 



"Of the salts removed, the most injurious one, when present in sufficient quantity, 

 is the sodium carbonate. . . . Sodium t'arbonate does not seem to be retained by 

 the soil, or removed from solution by passing through it, while the sodium sulphate, 

 or white alkali, is retained to a very marked extent." In the analyses reported the 

 amounts of sodium carbonate in the ground water varied from 10 to 28 gr. per gallon, 

 in the drain water froui 11 to 23; sodium sulphate in ground water 89 to 105 gr., in 

 the drain water 5 gr. The amounts of sodium chlorid and calcium and magnesium 

 sulphates were also considerably less in the drain water than in the ground water. 



"The amount of potash salts removed by the drain water [about 5 lbs. i)er acre- 

 foot of water] was less than that found in solution in the ground water. . . . The 



