53 



The soluble chloride of lime could apparent!}' also be used to advan- 

 tage upon a soil which is strongly impregnated with alkali. With 

 this salt the best effects would be anticipated when it is used as a rem- 

 edy for black alkali, although it is likewise a powerful antidote for the 

 chloride and sulphate of soda and of magnesia. But, except in rare 

 instances, the use of chloride of lime upon a large scale is hardly i)rac- 

 ticable. The little-soluble carbonate of lime is likewise more or less 

 beneficial in all cases except that of black alkali, but it is a much 

 less powerful remedy than is land i>laster (calcium sulphate). 



Much economic value should attach to an extension of these experi- 

 ments by using mixtures of more than two salts. It would thus be 

 possible to imitate more closely the conditions which obtain in alkali 

 soils, where several or all of these salts usuall}" occur together. 

 Furthermore, other kinds of plants should be tried in order to deter- 

 mine to what extent plants differ one from another in their power to 

 resist the effect of various combinations of alkali salts. In this con- 

 nection experiments should be made with wheat, barley, sugar beets, 

 and other important crops of the region, as it may be found that one 

 crop is better adapted than another to withstand the effects of this or 

 that type of alkali soil. 



This leads to the possibilitj' of selecting alkali-resistant breeds of 

 each of the leading crops. By observation of a stand of wheat or of 

 alfalfa which has been injured by the "rise of alkali" or by the use of 

 alkaline irrigating water, it is usually possible to find here and there 

 individual plants which have succeeded in surviving the injurious 

 effects of the salts. Similar differences in the power of individuals 

 to resist the action of alkali salts was detected in the culture exper- 

 iments. By continued selection of the seed of such resistant individ- 

 uals, sowing it season after season in alkali soil, there is reason to 

 hoi^e that in time a race could be developed and fixed which would 

 flourish in soils containing a greater amount of alkali than can be 

 endured b}' the ordinary agricultural varieties.^ It will likewise be 

 ver}' interesting to determine whether a race bred to resist black alkali, 

 for example, will also prove to be proportionately resistant to white 

 alkali, or whether it will be possible and desirable to develop differ ■ 

 ent races to suit different types of alkali soil. An observation already 

 cited (see p. 34) would indicate that the different power of resistance 

 possessed by individuals of the same species of plant is brought out 



^Observations made by Roos. Ronsseaux, and Dugast [Ann. de la Science Agron., 

 ser. 2, 6ieme annee, 2, 336 (1900) J indicate such differences among the grapes culti- 

 vated in Algeria. It was found that of different varieties growing in the same 

 soil the fruit of some absorbed less sodium chloride from the soil than was taken 

 up by others. As the sale of wine containing too high a content of sodium 

 chloride is prohibited by law in France, the economic importance of this discovery 

 is obvious. Although the problem here involved is somewhat different from that 

 of the power of resistance to the poisonous effects of a salt upon the plant, it serves 

 to illustrate the general principle that different individuals or races show marked 

 dissimilarity in their behavior in the presence of a given soil component. 



