27 

 ALKALI SOILS. 



A soil is composed chie'ly of the following elements in varying 

 compounds and proportions: Silicon, iron, aluminium, calcium, magnes- 

 ium, sodium, potassium, manganese, sulphur, carbon, oxygen, hydro- 

 gen, nitrogen, phosphorus, and chlorine. Should any one or several 

 of these compounds occur in proportions out of the normal, the soil 

 is designated by that peculiarity. Some of the Hawaiian soils, for in- 

 stance, contain abnormal quantities oi iron and aluminium and are 

 therefore distinguished as a particular type of soil. Alkali soils are soils 

 distinguished by a predominance of the compounds of the elements 

 of sodium, calcium, magnesium, and often potassium. The compounds 

 may be in the form of sulphates, carbonates, chlorides and nitrates in 

 varying quantities; those usually predominating are sodium carbonate, 

 sodium sulphate, sodium chloride and the corresponding compounds 

 of magnesium and calcium. 



FORMATION OF ALKALI SOILS. 



If soil and salt are mixed together and water filtered through and 

 collected, the water will be found to contain some of the salt that was 

 mixed with the soil. If the water containing the salt is passed into 

 soil containing no salt and not allowed to drain through, the water 

 on evaporation will leave the salt in the soil.* If more water con- 

 taining salt is passed into the soil and allowed to evaporate, it also will 

 leave salt behind increasing the amount added by the first application of 

 salty water. If this is repeated a number of times, the soil will contain 

 crystals of salt, and if the amount is sufficient the once fertile soil will 

 not support ordinary plant life.** 



(*) Water may pass into soil not only from above the surface, as when a piece of 

 land is irrigated or rained on, but it may be drawn up to the surface layer of soil from 

 the underground drainage waters by capillary action. 



(**) A striking instance of this occurred on an estate in Hawaii as described in an arti- 

 cle in "The American Sugar Industry And Beet Sugar Gazette," from which we quote: 

 "***Up to about fouryears agoit was a steady dividend paying corporation with a stock 

 quoted above par. It had fertile lands, though not a great acreage, and an abundant 

 supply of artesian water which was pumped into the irrigation ditches by a pumping plant 

 of good construction and large capacity. As none of the water had to be pumped to any 

 great elevation, the expenses of pumping were not excessive, and the plantation made 

 money. But there was salt in the water that was pumped on the land. There was not a 



