398 IRRIGATION PRACTICE 



alkali land, does fairly well, as do also sugar beets, sorghum, 

 kafir corn, rye, the date palm, grape-vines and many 

 other crops which yield annual crops of fair size in the 

 presence of relatively large quantities of alkali. 



The theory of reclaiming alkali lands by cropping is 

 that each crop absorbs from the soil considerable quan- 

 tities of alkali, and as cropping is continued year after 

 year, there is diminution in the alkali content of the soil 

 corresponding to the quantities removed by the crops. 

 The Australian salt-bush, containing about 20 per cent 

 of ash, may yield five tons an acre, which means each 

 crop removes from the soil about one ton of alkali. This, 

 continued for several years, would tend to make an alkali 

 soil better capable of producing ordinary crops. 



On alkali soils, deep-rooted plants do better than 

 shallow-rooted plants, and leafy plants do better than 

 those giving less shade. Legumes do not resist alkali well, 

 while the sunflower family does exceedingly well in the 

 presence of alkali. The fiber plants, such as flax, are 

 sensitive to alkali. Much information is yet needed con- 

 cerning alkali-resistant plants; the conditions under 

 which they thrive best, and the degree to which they are 

 able to remove alkali. Much new work can profitably be 

 done on this branch of the subject of alkali. 



237. Chemical treatment for alkali. The suggestion 

 has been made repeatedly that something might be added 

 to the soil to neutralize alkali. The chemical nature of 

 the constituents of alkali makes it difficult to make them 

 insoluble or to change them into something less obnoxious. 

 The conclusion has been reached, after much experi- 

 mentation, that only sodium carbonate may be corrected, 

 practically, by chemical treatment. Hilgard demon- 

 strated many years ago, on the California experimental 



