652 
Journal of Agricultural Research voi. xxvn, no. 9 
a part of the salt away by leaching. This can be done of course only 
where the soil is permeable to water and where the conditions of under¬ 
drainage are such that the soil does not become permanently saturated or 
water-logged. 
Fronj this statement of the case, it might be inferred that the reclama¬ 
tion of so-called 4 ‘alkali land” is not a very serious undertaking. As a 
matter of fact, such reclamation has been found to be very difficult if not 
impossible in some cases. On the other hand, there have been many 
instances where it has been both easy and successful. 
It is naturally a matter of a good deal of importance to be able to 
determine in advance whether a tract of salty land can be reclaimed at a 
reasonable cost. The cost of providing drainage outlets and of preparing 
the land for irrigation may be large. If this expense is incurred and it is 
then found that the land does not become productive as a result of the 
work done upon it, the investment is lost. 
The essential feature of the reclamation of salty land is the dilution 
of the soil solution. This is done by applying water of low salt content 
to the surface of the soil, to soak down through, dissolving out the soluble 
material or displacing the more concentrated soil solution, and then by 
providing drainage outlets for the salty water where such outlets are 
needed. In this process of diluting the soil solution in a salty soil the 
reaction of the soil to the change in the character of the solution is a 
matter of the greatest importance. It sometimes happens that this 
reaction is very slight; that is, that the physical character of the soil, 
particularly as regards its permeability to water, remains practically 
unchanged. Unfortunately, this is not always true. There are many 
examples of attempts to reclaim salty soil by leaching that have been 
given up because when the concentration of the soil solution was reduced 
the soil became nearly or quite impermeable to the further movement 
of water through it. 
These differences in the reaction of the soil to the dilution of its 
solution have led to corresponding differences of opinion as to the possi¬ 
bilities of reclaiming salty land. In some regions one finds that irrigation 
farmers are confident that such land can be reclaimed if adequate 
drainage is provided and the land is thoroughly irrigated. In other 
regions one finds an equally firm conviction that when a tract of land 
has once become salty it is permanently ruined. 
The fundamental reason for these observed differences in the reaction 
of the soil has not been clearly understood, but more light has been 
obtained as a result of recent investigations. The reactions that take 
place in the field may now be duplicated in the laboratory. When this 
is done it is found that the differences in soil reaction as the soil so¬ 
lution is diluted are associated with differences in the character of the 
material in the soil solution. 
Where investigators working with salty soils have identified only the 
acids in the solution, they have observed that the reaction toward 
impermeability has been associated with a high proportion of carbonate. 
From this it has been inferred that sodium carbonate, or “black alkali, ,f 
is the chief cause of the impermeability of the soil. 
Other investigators who have identified the basic constituents of the 
soil solution a,s well as the acids have found that when these bases 
consist chiefly of calcium and magnesium the soil does not show much 
