29 



If by copious rains these salts could be dissolved and carried to the 

 sea, the soils would be normal soils. Or if irrigation water were allow- 

 ed to run over the soils and the soils properly drained, they would 

 be normal soils. Alkali lands are caused, then, by deposits of easily 

 soluble salts in lands where there is not sufficient water or proper 

 drainage to remove them. Alkali will usually be found in the lower 

 levels. In the Chicama valley, for instance, the salts have 

 been carried from the upper to the lower portions and because they 

 could not find their way to the sea, have been held and accumulated. 

 There is a splendid example of the formation of alkali lands now going 

 on on one of the estates near Lima; the waters from the mountains 

 are concentrated in a large sink hole that is difficultly drained; the 

 salts are being deposited and the alkali is becoming so strong that the 

 surface crust will burn the tongue in exactly the same way as sal soda. 



In countries where there is rain, this same dissolving of salts from 

 the mother soil goes on, but the rains prevent the accumulation. Na- 

 ture has her compensations; and though the rains prevent the accumula- 

 tion of alkali by carrying off the salts to the sea, they also carry off 

 some of the elements valuable for plant growth, so that where there 

 is much rainfall the soils generally, are not so rich in mineral plant 

 food as in districts of little rainfall. Alkali lands must not, therefore, 

 be classed as poor or bad lands. 



Because the valleys are comparatively short and slope gently to the 

 sea, and because there is an excellent natural drainage system, the al- 

 kali lands in Peru will never become so extensive nor so difficult to 

 handle as in many other countries having soils of this nature. 



LOCAL DISTRIBUTION OF ALKALI IN THE VALLEYS. 



While the formation of the alkali lands was due, primarily, to the 

 action of river waters, the alkali was confined to smaller limits than 

 at present, and its distribution may be accounted for by the irrigation 

 waters. 



Many of the valleys have been under cultivation for hundreds of 

 years. The water for irrigation was obtained from the rivers and was 

 distributed over the valley by the construction of dams, aqueducts 

 and sub-ditches. The farmer appreciating the necessity for economy 

 in the use of the water, probably did not allow any more than was 

 actually necessary to leave the field, and the water on evaporation left 

 its salts until they accumulated in sufficient quantities to affect the 

 crops. Incrustations appeared on the surface of the soil, and the crops 



