ALKALI CONDITIONS IN SALT KIVEB VALLEY. 99 



situated on higher land." These plantations are so low that drainage 

 is impossible, and naturally the growth is poorer and the yield lower 

 than in better situations, but it is remarkable that even date palms 

 should be able to grow at all in such situations. 



ALKALI CONDITIONS IN RELATION TO DATE CULTURE IN THE SALT 

 RIYER VALLEY, ARIZONA. 



A recent soil survey of the Salt River Valley region made by Thos. H. 

 Means 6 shows that there are considerable areas, perhaps 1 per cent of 

 the land in the valley, where the amount of alkali in the soil is from 

 0.25 to 0.50 per cent, or enough to be dangerous for most crop plants, 

 and much more, perhaps 5 per cent of the land, contains over 0.5 per 

 cent where none but alkali-resistant crops can grow. Most of these 

 alkali spots are caused by the rise of the ground water in the lowest 

 levels, as a result of irrigation, until it comes so near the surface that 

 moisture reaches the surface and alkali is carried up from the subsoil 

 by the capillary currents of water. Such ground water has leached 

 from higher levels and is often charged with considerable amounts of 

 alkali. 



The water used to irrigate the Salt River Valley is diverted from 

 the Salt River and conducted to the fields in open ditches. The river 

 is low during summer and the water often contains a considerable 

 amount of harmful alkali in solution. Prof. R. H. Forbes, who made 

 a study of the water of the Salt River from August 1, 1899, to August 

 4, 1900, finds that from Jane 1 to August 4, 1900, the average content 

 of soluble salts was 139 parts per 100,000, of which only 8.2 parts per 

 100,000 consisted of the harmless gypsum, leaving 130.8 parts per 

 100,000, or 0.13 per cent of harmful alkali. Professor Forbes remarks 

 that "it is to be remembered that this year (1900) was exceptionally 

 dry, and the waters'were consequently concentrated for a longer than 

 usual time. Nevertheless, for a considerable portion of each year 

 these waters are low and salty in character, and it remains true that 

 their use (which is unavoidable) must be attended with remedial care." c 



Professor Forbes considers it probable that with the prevailing agri- 

 cultural practice of Arizona the use of irrigating water containing 

 100 parts of soluble salt per 100,000 is likely in a few years to cause 

 harmful accumulations of alkali. In view of this danger the great 

 value of. the date palm is obvious, since it can support very much more 

 alkali than is sufficient to kill other crop plants. 



Masselot F. Les dattiers des oasis du Djerid. In Bui. de la Direction de 1' Agric. 

 et du Commerce, Re"gence de Tunis, Vol. 6, No. 19, April, 1901, p. 132. 



& Means, Thos. H. Soil Survey in Salt River Valley, Arizona, Field Operations 

 of the Division of Soils, U. S. Department of Agriculture, 1900, pp. 287-332. 



Forbes, R. H. Bui. 44, Arizona Agricultural Experiment Station, Tucson, 1902, 

 p. 166. 



