8 BULLETIISr 502^ U. S. DEPARTMENT OF AGRICULTURE. 



ordinary conditions this is about all that is necessary to know in 

 order to forecast the probable difficulty that will be encountered 

 in bringing the land to a condition for cultivation subsequent to 

 drainage. 



Surface accumulations of the alkali salts shoiild not be taken as 

 conclusive evidence of a case of extreme alkali trouble, for when 

 the soil water rises to such a height that the surface of the ground 

 is kept moist by the capillary water, high evaporation results, and 

 as only relatively pure water passes off in this manner, it follows 

 that the salts are left at the surface. If this process continue for 

 sufficient time, heavy incrustations of salt may form on the ground 

 surface irrespective of whether the soil water is highly or slightly 

 alkaline, though the higher the percentage of alkali in the soil water 

 the more rapid the accumulation of the salts by evaporation. Con- 

 sequentl}^, the more alkaline the soil water the greater the necessity 

 for inmiediate relief by drainage. The necessity of the drainage of 

 those shale lands that have become water-logged is shown from a study 

 of the following tables. Table I contains the results of analyses of 

 soil water as discharged from 10 newly installed drainage systems 

 on tracts at one time under cultivation. Samples A and B in Table 

 II are two samples of seepage water through shale from a canal the 

 first season after construction. Sample C in Table II is seepage 

 water in a valley in the bad-land topography shown in Plate IV. 



Table I. — Analyses of drainage waters from systems in shales. 



(Tracts at some time mider cultivation.) 



Substance. 



lonn. 



Sulphuric acid (SO4) 



Carbonic acid (CO3) 



Bicarbonic acid (HCO3). 



Nitric acid (NO3) 



Chlorine (CI) 



Calcium (Ca) 



Majoiesium (Mg) 



Sodium (Na) 



Total. 



Jlypothtlical combinatioTis. 



Sodium carbonate (NaiCOa). .. 

 MaKnesium sulphate (MgSOi). 



Sodium nitrate (NaNOj) 



Sodium chlorid (NaCl) 



Sodium sulphate (Na^SOi) 



Calcium sulphate (CaSO^J. 

 Calcium bicarbonate fCa( 6003)2) 

 Calcium carbonate (CaCOs) 



Total 



Milligrams per liter (parts per 1,000,000). 



1915, 

 Feb. 1. 



467 



14.2 



41 

 517 

 381 

 111 



244 



1,236 



620 



1914, 

 May 26. 



8,566 



556 



398 



172 



428.5 

 1,016 

 2,156.7 



13,293.2 



5,030 

 545.6 

 28.3. 5 



5,860.5 

 835.5 

 738.1 



13,293.2 



1914, 

 Apr. 

 27. 



24,932 



12 



583 



1,2.53 



294 



427 



2,754 



7, 123 



37,-378 



13,633 

 1,718 

 485 

 19,975 

 773 

 774 

 20 



37,378 



1914, 

 Apr. 

 27. 



25,382 



15.2 



728 



982 



305 



452 



3,333 



6,178 



37,375.2 



16, 409 



1,346 



503 



17,346 



689 



967 



25.2 



37,375.2 



1914, 



June 



11. 



3,132 



348 



200 



156 



505.5 



362. 5 



540 



,244 



1, 795 



274 



257 



1,127 



1,.329 



462 



5,244 



1914, 



May 



13,320 



632 

 832 

 490 

 425 

 878 

 5,094 



21,671 



4,3)6 



1,140 



809 



13,798 



739 



839 



1915, 

 Mar. 

 30. 



G. 



10,508 



513 

 286 

 262 

 405 

 600 

 3,901 



16,475 



2,970 

 392 

 432 

 11,196 

 803 

 682 



1915, 

 Mar. 

 14. 



5,500 



427 

 443 

 378 

 453 

 570 

 1,606 



9,377 



9,37' 



1916, 

 Feb. 

 15. 



6,. 372 



861 



4,861 



232 



602 



1,315 



2,151 



16,394 



6,510 

 6, 664 

 382 

 609 

 1,085 

 1,144 



16,394 



1916, 

 Feb. 

 15. 



20,470 



50 



688 



7,614 



428 



492 



2,746 



7,442 



39,930 



13,593 



10, 438 



706 



13, 287 



904 



914 



39,930 



