THE IRRIGATION AGE. 



427 



angular and elongated. For several seasons this has 

 been noted. Not only have I noticed this on the irri- 

 gated compared with non-irrigated land, but I have seen 

 it illustrated on the plots that were well tilled com- 

 pared with those that were in sod or received poor till- 

 age. In an experiment that we have been running at our 

 home station at Corvallis with Yellow Newtowns, those 

 that were in sod when compared with the well-tilled fruit 

 have given this difference. The Yellow Newtowns on the 

 well tilled plot mature later, are more elongated, and are 

 brighter in color. Those that received poor care and 

 wera allowed to stand in the grass matured earlier and 

 had a deeper yellow at harvesting. This same tendency 

 we found illustrated in the young trees compared with 

 old ones, the elongation and angularity of ihe fruit being 

 an indication of vigor. 



Considerable influence has been noted as regards 

 color. This is especially true on some of the lighter soils 

 and where red apples are grown. Each year the irrigated 

 apples have had a brighter, more attractive color, and 

 are handsomer, while those on the dry checks were duller, 

 yet deeper in color. The trade wants the bright, live, at- 

 tractive apples. In a number of cases it was found that 

 irrigation had an influence on the succeeding crop. The 

 irrigated trees have more numerous and stronger fruit 

 buds. This difference can often be noted at the bloom- 

 ing time. This was especially noticeable this last spring. 

 The trees that had received more care and had had suffi- 

 cient moisture bloomed more heavily than those which 

 had not had as much moisture. Undoubtedly, under 

 proper conditions, irrigation will have an influence in 

 making the trees regular bearers. 



Under conditions that are equal, we find that irriga- 

 tion has a tendency to produce more wood growth. We 

 have noted that this is true even though the trees are 

 more heavily loaded wth fruit. More wood growth is ob- 

 tained from irrigation where the trees have not been 

 vigorously winter pruned and are getting ample moisture. 

 The difference between the dry check and a moderate 

 amount of water is greater than between a moderate 

 amount and an excessive amount. In one experiment 

 the increase in terminal wood growth of the irrigated over 

 the lighter or non-irrigated amounted to 12 inches, on an 

 average. 



As I have already said, there were less culls on the 

 irrigated than the non-irrigated land, the latter suffer- 

 ing for moisture, was then referring to the size. We 

 found, also, less culls due to calex cracking on the irri- 

 gated than on the non-irrigated lands. Varieties like the 

 Jonathan suffer greatly from calex cracking. Cracking 

 may occur at the stem, as well as at the calex. In most 

 cases this is due to the fact that file fruit hangs on the 

 tree too long. We found the fruit on the dry checks 

 matured earlier than on the irrigated plots. It showed 

 that irrigation had a tendency to cause the apples to 

 mature somewhat later, which meant that the irrigated 

 fruit was in rather better condition at picking time, and 

 we therefore had less cracking. Had the dry checks 

 been picked earlier there would have been less crack- 

 ing noted, probably, but it is sometimes almost impos- 

 sible to so pick the fruit as to avoid cracking. 



Irrigation tends to keep the leaves green later in the 

 fall, and to cause them to hang much longer on the trees. 

 In fact, if moisture is given the trees in the form of rain- 

 fall or irrigation so as to keep them in activity, we can 

 expect the results noted. In certain seasons there is 

 some danger of over-irrigation of young trees. This has 

 a tendency to prevent the trees hardening. I have noted 

 that the trees were sometimes more than a month later 

 in maturing when heavily irrigated than otherwise. 



I may cite a couple of experiments regarding foliage 

 coloring on the plots. Plot 1 received 600 gallons of 

 water to the tree in the middle of July, and again in the 

 middle of August. Plot 2 had 1,500 gallons to the tree 

 July 20 and August 25. On October 4 the foliage of the 

 trees on Plot 1 began to color, and to drop from many of 

 the trees. Plot 2 was still of a good, dark green color, 

 and by November most of the trees on Plot 1 had shed 

 a large per cent of their foliage, but though a few on 

 Plot 2 had done likewise, the larger number had not. 

 On most of the trees the foliage was just beginning to 

 turn. The trees which had a light crop tended to color 



earlier and drop their foliage earlier than those heavily 

 loaded with fruit. 



In a second experiment Plot 1 received 1,200 gal- 

 lons of water to the tree August 14, Plot 2, 865 gallons to 

 the tree July 27, Plot 3, 555 gallons to the tree July 27, 

 and Plot 4 was a dry check. On the dry check the 

 leaves began to fall and color by September 20, followed 

 by plots 2 and 3, the foliage of these maturing about the 

 same time. On Plot 1, where the trees received the 

 heaviest irrigation, the foliage remained green later, and 

 had not fallen late in November. 



One advantage in irrigation we have noted is in its re- 

 lation to the growing of cover crops. We found that on 

 the irrigated plots, not only did the natural weeds grow, 

 but the cover crops also made a much better growth than 

 on the dry checks. This will be a very important factor 

 in those orchards which are suffering because of a lack 

 of organic matter and humus. Irrigation will aid ma- 

 terially in building up the humus content of such soils. 



We have found that the irrigation practices in one 

 district will vary and that such differences can be at- 

 tributed to the kind of soil, variety of fruit, and age of 

 the trees. Such problems as the determination of the 

 exact time, to irrigate and the best methods to employ 

 will vary with the conditions stated. 



There is a great variety of soils on the Pacific slope. 

 The problem of irrigating some of these is somewhat 

 complicated. In some sections we have extremely heavy 

 types, such as the stickies or adobes, and experiment 

 shows that we generally get better results under culti- 

 vation without the use of irrigation water on such soils. 

 They are exceedingly difficult to irrigate, and if irrigated, 

 warm water should be used. Possibly the best way to 

 handle such soils would be to grow shade crops and use 

 the water for both trees and shade crops. 



On the lighter types of soil more water is needed, 

 especially where apples are grown. On the pumice soils, 

 or very fine type of volcanic ash, we found in southern 

 Oregon that at least 3,500 gallons of water to the 

 tree is necessary, distributed in about three equal irri- 

 gations in June, July and August. We obtained the best 

 results by allowing a small stream to flow down the fur- 

 row, increasing the amount to four inches to each furrow 

 as soon as the soil began to take up the water. In some 

 of the free soils in the Rogue River Valley we found that, 

 where they were properly cultivated, they responded best 

 with irrigation to the amount of 2,400 to 3,000 gallons 

 to the tree, in two irrigations. This kind of soil is low 

 in organic matter, takes water slowly, and to get an 

 even distribution it is necessary to have a large number 

 of furrows with a small amount of water in each. 



With experiments with 10-year old Newtowns on 

 river bottom soils, which vary from medium to slightly 

 heavy texture, fine results were obtained by applying 1,600 

 to 2,000 gallons to the tree, divided in two irrigations, 

 one in July and the other in August. This type of soil 

 takes up water freely, and a comparatively large head 

 to each furrow may be used. 



On some of the lighter granitic soils it is better to 

 use a number of furrows between each tree and its neigh- 

 bor, with a small head of water. In nearly all cases fur- 

 rows and rills are used, flooding having been practically 

 abandoned in the northwest. In a few cases where the 

 soil takes up water very slowly, however, if a sort of 

 check or basis system is used it will prove to be one of 

 the best systems. 



From some experiments we have conducted with 

 Bartlett pear trees 7 to 10 years of age, in good vigor, we 

 found that the application of irrigation water seemed to 

 have a tendency to make the trees more susceptible to 

 disease, such trees blighting more readily. Under con- 

 ditions where the pears were not making a normal growth 

 it is better to add water regardless of the age. 



The use of excessively cold water on pears is a 

 questionable practice. Many heavy soils crack, and the 

 cold water rushes down the cracks, interfering with the 

 root functions. From observation we are led to believe 

 the practice detrimental rather than beneficial. 



Experiments with Winter Nelis, d'Anjou and Bartlett 

 pear trees 18 years of age on a rather heavy type of soil 

 have been made, the orchard being divided into several 

 (Continued on page 447.) 



