WARM IRRIGATION WATER ADVANTAGEOUS. 49 



In many parts of California and possibly in some parts of Arizona 

 there is enough rainfall to support the date palm without irrigation 

 (see p. 124). The Wolfskill date palm at Winters, Cal., for example, 

 is never irrigated, yet bears abundant crops of good dates every year. 



In regions where the winters are very cold it is unwise to irrigate 

 late in summer, except when necessary to keep the palms alive, since 

 abundant watering forces a tender new growth, which is likely to be 

 killed by the freezes of the succeeding winter. At Tulare, in the San 

 Joaquin Valley, California, where there are from 6 to 34 severe frosts 

 every winter and where the temperature sometimes falls as low as 

 17 F. or lower, the gardeners of the substation of the Agricultural 

 Experiment Station consider it unwise to irrigate date palms after the 

 month of June. 



WARM IRRIGATION WATER ADVANTAGEOUS. 



The growth of the date palm and the maturing of its fruit are 

 hastened by supplying warm water to the roots. For example, in 

 the oasis of Chetma, Algeria (see PL XII and Yearbook, 1900, PL 

 LIX, fig. 8), largely supplied with water from warm springs having 

 a temperature of 94.1 F. (34.5 C.), the Deglet Noor date ripens 

 early in the season, especially on those trees growing near the 

 springs and which, consequently, receive warm water even in winter 

 and early spring, when the air is still cold. Biskra, near by and at 

 nearly the same level, though less protected against cold winds, is 

 also irrigated largely from springs, but the temperature of the water 

 of these springs is only 70 to 81 F. (21.5 to 27.33 C.), and the 

 water is cooled in winter and spring by admixture with the run-off 

 from the Atlas Mountains to the north and by flowing a couple of 

 miles in open canals before it reaches the nearest date palms. Here 

 the Deglet Noor date does not mature so well as at Chetma and is not 

 of the best quality. The artesian wells of the Oued Rirh country (see 

 map, PL II, p. 76) furnish water of a temperature ranging from 76.3 

 to 79 F. (24.6 to 26.1 C.), and in the Souf country the ground water 

 to which the palms send down their roots is much colder, having a 

 temperature of only 57.2 to 68 F. (14 to 20 C.); but in these regions 

 the summer heat is much greater than at Biskra and usually suffices to 

 enable the Deglet Noor to mature perfectly. 



In the Salt River Valley, Arizona, the irrigation water is conveyed 

 in open canals mostly shaded by cottonwood trees. The temperature 

 of the water naturally varies with the season. In June, when the tem- 

 perature of the air ranged from 82 to 104 F., Professor McClatchie 

 found the temperature to range from 73 to 94 F. in the canals and 

 from 82 to 88 F. in the smaller irrigating ditches. It should be 

 noted that in June the supply of irrigating water is less than for any 

 other month of the year, and probably in February, March, and April, 



13529 No. 5304 4 



