180 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



easily soluble and widely distributed through the agricultural soil, 

 may be concentrated by careless handling of the water and bring about 

 a condition which is covered by the general term " alkali." These 

 salts appear on the surface of the ground, usually as a thin white 

 crust, looking in the distance like snow (pi. 2, fig. 2). The appear- 

 ance of the salts on the surface is sometimes preceded by an excessive 

 crop yield, followed by diminution and burning out of the plants, 

 "and then by the white patches taking possession of the field. This is 

 commonly known as the white alkali. Another appearance, less fre- 

 quent, is that of irregular black patches of a peculiar, almost oily 

 substance, as though a quantity of crude petroleum had been scat- 

 tered over the field, destroying the crop and leaving a black stain. 

 This is the dreaded black alkali, which is more difficult to eradicate. 



The white alkali is of the nature of gypsum, mostly sulphate of 

 soda, while the black alkali consists of mixtures of similar salts in 

 which the bicarbonate of soda predominates. Their destructive effect 

 can be prevented by care and vigilance, and remedies can be applied, 

 though at very large expense, sometimes too costly for the value of 

 the land. In this, as in many other evils, an ounce of prevention is 

 worth a pound of cure. 



A study of the origin of the alkali shows that as a rule where water 

 has been applied to lands in excessive quantities it has dissolved some 

 of the valuable salts, and, seeping through the ground, has finally 

 come to the surface perhaps a mile or more away. Evaporating, the 

 water has left its load of soluble material, for a time enriching the 

 soil at this locality, as illustrated in the large crop growth for a short 

 period. The process still continuing, the salt has accumulated to 

 such an extent as to be visible. 



The remedy lies in two directions : 



First. In preventing excessive use of water, and, 



Second. In systematic drainage, to take away any excess of water. 



The first is mechanically the easiest, but from the human stand- 

 point the most difficult, as it is impossible to convince the average 

 newcomer, who first sees the wonderful results of irrigation, that it 

 is possible to apply too much water and to ruin his own or his 

 neighbor's field. 



He can not see that he is washing out slowly but surely the con- 

 stituents of the soil which are vital to his continued success. It 

 requires a careful analysis to show that these salts, which would cost 

 him, say, $100 per acre to apply, can be quickly taken away by a little 

 carelessness, and the true value of the land reduced. He is less 

 willing to admit that the excess water which has drained or perco- 

 lated from his land, carrying off what is valuable to it, is at the same 

 time concentrating the salts in the soil of his neighbor until its value 



