ipiS 



BETTER FRUIT 



Page 5 



Orchard Irrigation Question in the Pacific Northwest 



[Editor's Note — This article was written by 

 Mr. Allen when superintendent of Umatilla Ex- 

 periment Farm. Mr. Allen is now agriculturist 

 on reclamation projects.] 



THE methods and practices involved 

 in tlie irrigation of orchards in the 

 Pacific Northwest, wliere a wide 

 range of soil, topographical and cli- 

 matic conditions exist, are continually 

 undergoing changes and improvements. 

 The destructive and costly system of 

 clean cultivation has at last given way 

 to systematic cropping of orchard soils 

 witli legumes which produce profitable 

 crops and are valuable as soil builders. 

 This change in soil treatment created 

 a demand for difTerent methods of irri- 

 gation in numerous instances, and 

 forced upon many districts more eco- 

 nomical use of irrigation water. These 

 changes all appear to be to the best 

 interest of the fruit industry, as with 

 each change has come better and more 

 economical practices. 



There are three phases of the opera- 

 tion of irrigating an orchard properly, 

 all of which directly influence the suc- 

 cess of the fruit grower. They involve 

 (1) supplying the trees and fertilizer 

 crop with water in correct amount and 

 at the proper time; (2) handling the 

 water in the manner best suited to the 

 water-holding capacity, slope and 

 character of the soil; and (3) economy 

 in the amount of water used and efii- 

 ciency of labor involved in irrigating. 



When clover and other crops are 

 planted in orchards it must be with a 

 realization that they require a liberal 

 supply of moisture, and provision must 

 be made to supply a sufllcient amount 

 to satisfy the needs of the fruit and 

 clover crop. To fail in this results in 

 heavy loss of fruit and unsatisfactory 

 growth of the fertilizer crop. 



A common error in irrigating or- 

 chards is to make the first application 

 of water too late in the spring. This 

 frequently results in the dropping of 

 much fruit; not infrequently the entire 

 crop falls, soon after it is set. Drouth 

 frequently occurs between irrigations 

 where improper care is exercised. 

 Superficial examination of the soil, or 

 an endeavor to judge from the appear- 

 ance of the trees when they require 

 water, does not convey a correct under- 

 standing of the conditions under wjiich 

 the trees are working. The first prac- 

 tice might result in irrigation being 

 applied prematurely, thus resulting in 

 waste of water and time. The second 

 practice invariably results in a measure 

 of drouth existing before the trees show 

 signs of distress. Ordinarily irrigation 

 should be applied before the soil begins 

 to fall apart after being pressed firmly 

 together in the hand, lis falling apart 

 indicates an insuflicient quantity of 

 water present to hold the soil particles 

 together, which in turn indicates a 

 scarcity nearly critical to plant growth. 

 Since trees feed to considerable depth, 

 it is important to know that sufficient 

 moisture is present at all times to the 

 full depth of the roots. It is important 

 to irrigate while the soil is yet moist. 



By R. W. Allen, Hermiston, Oregon 



for then it takes up the water more 

 readily and more uniforml.\' than when 

 it becomes dry. The air in a dry soil 

 gives way slowly to the entering water, 

 thus rendering irrigation much slower 

 than if there is moisture jjresent. 



Three causes appear to influence the 

 late use of water. Insudicient atten- 

 tion is paid to the conditiiui of the soil 

 to determine when irrigation should be 

 applied. The occurrence of light show- 

 ers which do not materially influence 

 the amount of soil moisture is often 

 considered proof that irrigation is not 

 necessary. Inadequate facilities for 

 hastening the operation of irrigating 

 frequently results in a portion of the 

 land becoming badly in need of water 

 before it can be reached. This results 

 from beginning too late, or from using 

 too small a head of water. Consider- 

 able loss of fruit has occurred from 

 early drouth, and will continue to oc- 

 cur until earlier irrigation is practiced. 

 This is particularly true where small 

 irrigation streams are used. Larger 

 quantities of water run together would 

 permit the work being rushed, whereas 

 it cannot be hurried with a small 

 stream of water. 



The time to irrigate varies so much 

 for different types of soil, and the ex- 

 tent of crop growth, that the practice 

 for each orchard or portion of an 

 orchard becomes a problem in itself. 

 Land upon which heavy vegetable 

 growth is taking place can be irri- 

 gated later in the fall than under con- 

 ditions influencing the removal of little 

 moisture from the soil. Trees carrying 



heavy crops of fruit should be kept 

 well irrigated up to picking time. They 

 are seldom injured by late irrigation 

 unless it is excessive, as their energy 

 is largely devoted to maturing fruit 

 rather than the growth of branches. 

 When rapid growing trees reach the 

 age at which they should begin fruit- 

 ing they should be caused to grow 

 slowly, by proper manipulation of the 

 irigating to influence the formation of 

 fruit buds. 



The frequency at which water should 

 be applied to orchard soils depends 

 upon the amount they are capable of 

 storing, the extent of loss by evapora- 

 tion and the quantity required by the 

 crop, ^\^len the capacity of the soil 

 to retain moisture is small, as it is in 

 coarse or shallow areas, the length of 

 time it can maintain normal crop 

 growth is proportionately less than for 

 a soil having greater storage capacity. 

 Orchards on coarse, sandy soil require 

 irigation at intervals of ten to fifteen 

 days during the active growing season. 

 Those on silt and clay loam soils of 

 adequate depth require two to four irri- 

 gations a year. One irrigation in May 

 or .lune might suffice on very retentive 

 soils, but it is better practice to irri- 

 gate oftener and use less water at each 

 irrigation. In this way a more uniform 

 moisture content of the soil is main- 

 tained. Where orchards are found to 

 require irrigation at intervals of two, 

 four or six weeks, it is reasonable to 

 expect that they would require irriga- 

 tion at approximately half this period 

 when two full crops are drawing from 



Kioiui. 1- 111) Sli.illuw furrows are desirable for row crops and f"i- starting 



clover or all'alfa. ( '• ) Shallow furrow on left, and comparatively deep furrow 



on right, showing r\lcnt of surface wetting of the soil when water has run for 



the same time in each. 



