Winter Irrigation of Deciduous Orchards. 237 



manuring crop, and at the same time store enough water in the 

 soil to carry the orchard through the hottest and dryest summers. 

 Judging by observations, and by consultation with orchardists, 

 this amount is frequently applied during the summer to maintain 

 the orchard alone, with no better results than were secured last 

 summer by winter irrigation alone. 



SUMMARY AND CONCLUSIONS. 



1. Fruits can be grown in the valleys of southern Arizona 

 only by irrigation, the supply of water for which coming from 

 the higher elevations where precipitation is much heavier. 



2. The heaviest rainfall is during mid-summer, but the 

 largest supply of irrigating water is during the winter, the sup- 

 ply during the latter period being over three times what it is dur- 

 ing the former. 



3. The general practice previous to beginning the experi- 

 ments was to irrigate orchards once or twice a month, from 

 February or March until October, the belief being quite general 

 that under the trying summer conditions of the region winter 

 irrigation was of little value, or at least entirely inadequate. 



4. The purpose of the experiments was to determine how 

 much summer irrigation might be rendered unnecessary by the 

 liberal application of water during winter when the supply was 

 comparatively abundant. 



5. During the first year of the experiment the orchard was 

 irrigated eight times from January 9 to March 30, 1899, followed 

 by thorough plowing and summer cultivation. The only water 

 applied during the summer was a small amount to three-fifths of 

 the orchard June 24. 



6. The climatic conditions of the growing season of 1899 

 were somew T hat more unfavorable than usual, the rainfall being 

 about normal, the relative humidity some below normal, and the 

 temperature above normal. 



