WATER SOILS. 791 



because of large surface area; for even in the small number of soils represented in 

 the above analyses there are many which, though having very high clay percentages, 

 are low in their moisture and water coefficient, and vice versa. 



"(2) There are in the soil certain chemical compounds (zeolites, ferric, silicic, and 

 alnminic hydrates and humic compounds), which are highly hjgroscopic and absorp- 

 tive in themselves, and are held almost exclusively by the clay in greater or lesa 

 amounts. The proportion of these,. singly or conjointly, seems to have a greater, if 

 not a controlling, influence over that power than the mere amount of clay and fine 

 material, as such. 



"(3) The upward movement of water in soils is controlled in rapidity by the pro- 

 portion of coarse material; and the limit in height to which water will rise by 

 capillarity is deiiendeut upon the amount of tine silt and clay. The extreme height 

 reached thus far, under the most favorable conditions, is 50 in., even after several 

 months. In sandy soils the limit was less than 18 in. 



"(4) The presence of allialine salts in a soil produces a puddling or dcflocculation 

 of the particles when wet, and a consequent compact condition, which prevents the 

 rapid rise of water. This puddling is accompanied by large contraction of volume, 

 a feature which to a far less degree has been observed in other soils. On the other 

 hand there are some soils (adobes and certain ferruginous clays), which, when wet, 

 expand quite cousiderably, because of the swelling of the colloidal particles. 



The amount and kind of soluble salts present in different por- 

 tions of an alkali spot, from the center to the circumference, 



C. COLEMORE and E. W. Hilgakd {California Sta. Kpt. 1893 and 1894, 

 yp. 140-145). — Tabular statenieuts of analj^ses showing the amount and 

 coniposition of the alkali salts talc en at 5 different distances from the 

 center of an alkali spot are rex)orted and discussed. It was observed 

 that there was a more or less regular decrease in the amount of the 

 alkali salts toward the margin, beyond which normal vegetation would 

 thrive. In this case the maximum amount "found to be compatible 

 with ordinary (weed) vegetation was 0.23 per cent, or a little less than 

 a quarter of 1 per cent of total soluble salts, of which, however, one 

 third was carbonate of soda and nearly another third common salt, or 

 nearly 0.08 per cent of the soil of each." It has been observed, how- 

 ever, that this amount of carbonate of soda in an adobe soil is sufficient 

 to i^revent the growth of any useful i)laut. ''It is therefore obvious 

 that the mere determination of the amount of total salts present in a 

 soil is not sufficient to determine its fitness or unfitness for crop growth. 

 It is essential that the nature and proportion of the different salts pres- 

 ent should be determined before a definite judgment can be had." 



The analyses show further that the alkali containing the highest 

 amount of carbonate of soda also contained the largest proportion of 

 organic matter; that the i^er cent of soda steadily increased from the 

 margin toward the center, while the reverse was true for potash ; that 

 carbonic acid and phosphate increased from the circumference toward 

 the center; that chlorin decreased from the margin toward the center, 

 while the proportion of nitrates was greatest at a point about halfway 

 between the margin and center. 



Reclamation of alkali land Tvith gypsum at the Tulare Station, 

 C. H. SHmw and E. W. Hilgakd {Calif oniia Sta. Ej)t. 1893 and 1894, 



