TIME OF IRRIGATION 179 



fall and increasing the duty of irrigation water through 

 the growing season. The most notable of these studies 

 was made in 1898 and 1899 by McClatchie, in an Arizona 

 valley where the annual rainfall averages about 11 inches, 

 and is so distributed as to be heaviest from July to Sep- 

 tember and from December to February. Deciduous 

 trees shed their leaves in November; the buds start in 

 February, and the leaves are generally out by the end of 

 March. Heavy frosts often occur in December and 

 January. The orchard used for the experiments contained 

 chiefly peaches and apricots planted in 1892. In 1898, 

 the orchard was irrigated in September. Then, from* 

 January 2 to March 1, 1899, the orchard received eight 

 irrigations. It was then plowed and harrowed. From 

 March 31 to June 24, 1899, no further irrigation was 

 applied and no rain fell during that tune. In spite of the 

 lack of irrigation the growth of the trees and the yield of 

 fruit were excellent. On December 16, 1899, the winter 

 irrigations began again and 3 acre-feet of water were ap- 

 plied between that date and March 5, 1900. During the fol- 

 lowing eight months no irrigation water was applied, and 

 the rainfall during that period was only about 2% inches, 

 distributed among five rains. At the end of the eight 

 months the trees were in fine condition and the yield of 

 fruit was excellent. The season was the driest and hot- 

 test on the records of the state. 



This classical experiment demonstrates conclusively 

 the high crop-producing value of fall and winter irriga- 

 tion, correctly applied in districts where such irrigation 

 is at all practical. It reemphasizes also the doctrine that, 

 when the soil is used as a storage reservoir, it is not neces- 

 sary that much water be added during the growing sea- 

 son of the crop. 



