UTILIZATION AND RECLAMATION OF ALKALI LANDS. 463 



impenetrability of the surface soil itself will render even under- 

 drains ineffective unless the salsoda and its effects on the soil 

 are first destroyed by the use of gypsum, as above detailed. 

 This is not only necessary in order to render drainage and 

 leaching possible, but is also advisable in order to prevent the 

 leaching-out of the valuable humus and soluble phosphates, 

 which are rendered insoluble (but not unavailable to plants) 

 by the action of the gypsum. Wherever black alkali is found 

 in lands not very sandy, the application of gypsum should 

 precede any other efforts toward reclamation. Trees and 

 vines already planted may be temporarily protected from the 

 worst effects of the black alkali by surrounding the trunks with 

 gypsum or with earth abundantly mixed with it. Seeds may be 

 similarly protected in sowing, and young plants in planting. 



Swamping of Alkali Lands. It should, however, be remem- 

 bered that the swamping of alkali lands, whether of the white 

 or black kind, is fatal not only to their present productiveness, 

 but also, on account of the strong chemical action thus induced, 

 greatly jeopardizes their future usefulness. Many costly in- 

 vestments in orchards and vineyards have thus been rendered 

 unproductive, or have even become a total loss. 



Reduction of Alkali by Cropping. Another method for 

 diminishing the amount of alkali in the soil is the cropping 

 with plants that take up considerable amounts of salts. In 

 taking them into cultivation, it is advisable to remove en- 

 tirely from the land the salt growth that may naturally cover 

 it, notably the greasewoods (Sarcobatus, Allenrolfea}, with 

 their heavy percentage of alkaline ash (12 to 20 per cent). 

 Crop plants adapted to the same object are mentioned farther 

 on. Such crops should also, of course, be wholly removed 

 from the land. 



Total Amounts of Salts Compatible with Ordinary Crops; 

 Tolerance of Culture Plants. Since the amount of alkali that 

 reaches the surface layer is largely dependent upon the varying 

 conditions of rainfall or irrigation, and surface evaporation, it 

 is difficult to foresee to what extent that accumulation may go, 

 unless we know the total amount of salts present that may be 

 called into action. This, as already explained, can ordinarily 

 be ascertained by the examination of one sample representing 



