SOIL DEFICIENCIES 267 



tilth of the land is decidedly improved. If much alkali is present, 

 gypsum alone will not be sufficient because it does not remove the 

 alkali, but merely changes it to another form. No chemical treat- 

 ment is known which will counteract the effects of white alkali. 



(3) Scraping the Surface. At the end of a dry season, when 

 the alkali has risen to the surface, it may be scraped off and 

 carted away. This method might be used for small spots. 



(4) Flushing the Surface. This method consists in flooding 

 the land with water and drawing it off after a short time. This 

 method can not be used for any soil in which the water sinks in 

 rapidly, because the water will carry the alkali with it into the 



soil. With rather heavy, impervious soils, with the alkali largely 

 at the surface, the method may prove successful. 



(5) Flooding Without Drainage. For this method, the soil 

 must be naturally well under-drained, with the water table several 

 feet below the surface. The water used in flooding must go 

 through the soil, and into the drainage. The method employed is 

 to level the field, and cover the soil with water to the depth of 

 several inches, the water being held on the soil by means of dikes 

 or levees so that it soaks into the soil. Repeated flooding will 

 carry the alkali out in the drainage waters. As already 

 pointed out, this method can only be applied to soils which are 

 naturally well under-drained, and on which the flooding will not 

 raise the level of the water-table to a dangerous extent. 



(6) Flooding and Drainage.^ Flooding together with artificial 

 drainage will reclaim any alkali land; provided, of course, that 

 the flooding is carried out often enough, and with sufficient water, 

 and provided that the drainage is sufficient. Drainage is largely 

 a matter of engineering. The drains should be at least three feet 

 deep; on some soils four or five feet is better. In heavy soils 

 they should be from 25 to 100 to 150 feet apart; in sandy soils 

 intervals of 250 to 300 feet may answer the purpose. 



Prevention of Alkali. Accumulation of an excess near the 

 surface is most to be feared. If the alkali is below the root zone 

 of the plants it can do no damage. Plants may grow and do well 

 1 Bulletin 34, Bureau of Soils, also Bulletin 44. 



