320 IRRIGATION PRACTICE 



irrigated, or very cautiously, when they are in bloom; for 

 such early irrigation is said to interfere with the setting 

 of the fruit. The proof of this has not yet been made. As 

 the hot season advances, water is needed, but the first 

 irrigation should be postponed until really needed by the 

 orchard. In Washington, where the season begins early and 

 there is a high annual rainfall, the first irrigation comes in 

 late April or early May, followed by three or four irriga- 

 tions, from twenty to thirty days apart. In the drier parts 

 of the arid region, where spring comes later, the first irri- 

 gation can be postponed until June or even July. In the 

 Hood River Valley of Oregon, soils well saturated in the 

 spring need no further irrigation until about July 15. In 

 Colorado, water is applied to an orchard from two to five 

 times a season. In Idaho, where the first irrigation comes 

 about June 15, three irrigations in a season are said to be 

 sufficient. The Utah practice is the same as that of 

 Idaho. As an average, two to four summer irrigations, 

 of 3 to 7 acre-inches each, and one fall irrigation should 

 be sufficient for deciduous fruits. This means that if irri- 

 gation begins in June there will be one irrigation every 

 three or four weeks throughout the summer season. 



Orchard soils should not be allowed to dry out too 

 much, for an excessive dryness in early or middle summer 

 will injure the tree for the whole season. On the other 

 hand, over-irrigation tends to decrease fruit-production 

 and delay the ripening of the fruit. The farmer, therefore, 

 must remember not to check the growth of the fruit tree 

 by too little irrigation, nor to irrigate so heavily that the 

 formation of buds is decreased and ripening delayed. 

 Fruit trees make little growth after July 15, when the 

 fruit-buds for the following year are being made. Exces- 

 sive irrigations at this time, which force continued 



