2378 



ORANGE 



ORANGE 



soil. Upon shallow soils, trees will succeed for a while, 

 but artificial feeding must be resorted to earlier. No 

 soil less than 2 feet deep should be considered safe for 

 oranges. Soils underlaid by hardpan, or layers of open 

 gravel are apt to cause functional derangements of the 

 nutrition of the trees. The ideal soil is a friable easily 

 worked loam, 8 or more feet deep, growing gradually 

 lighter in color and texture as the depth increases. This 

 not only provides a large storehouse of plant-food but 

 a great reservoir to hold water. Of the two most 

 common conditions, it is much better to have a light 

 topsoil over heavy clay subsoil than a heavy clay top- 

 soil over sand or gravel. 



It is the custom to plow the orchards once a year, 

 usually in the spring at the time of turning under the 

 green-manure crop. Throughout the spring and sum- 

 mer, the soil is clean cultivated to a depth of 4 to 8 

 inches. Thorough cultivation and the reestablish- 

 ment of the dust mulch follows each irrigation during 

 summer. For this work, either disc, spike-tooth cul- 

 tivators, or spading harrows drawn by three or four 

 horses are used. Orchard tractors are beginning to take 

 the place of horses in the interior valleys. In some soils, 

 the oft-repeated tramping of the horses causes the 

 formation of a "plow-sole" which interferes with the 

 downward course of the irrigating water. This may be 

 broken up every second or third year by running a sub- 

 soil plow through the middles in such a way as to cut 

 as few of the large roots as possible. Some growers have 

 abandoned all tillage and cover the ground 8 or 10 

 inches deep with mulch. The trees do well under this 

 system but the mulching material is expensive and the 

 danger from fire during the dry season is very great. 



California soils are, as a rule, noted for their low con- 

 tent of humus. It is imperative that the humus-con- 

 tent be increased and maintained by generous addi- 

 tions of organic matter. The chief source of humus is 

 the vetch green-manure crop, but where the trees are 

 large and shade the ground, the growth of vetch 

 amounts to little, and other means must be resorted to. 

 Large quantities of stable manure, grain, hay, lima- 

 bean straw, and even alfalfa hay, have been used for 

 this purpose, and of late attention has been called to 

 the possibility of using kelp, which is plentiful along 

 the Pacific coast. How to maintain a high humus- 

 content hi the soil is today one of the chief problems 

 before the industry. 



Commercial fertilizers are commonly used and in 

 increasing amounts from the time the trees are five or 

 six years old. There is probably more difference of 

 opinion and diversity in practice hi connection with 

 the use of commercial fertilizers than with any other 

 phase of the business. The amount of application runs 

 from two to forty pounds to each tree, annually, 

 depending upon its size and age. Some apply the fer- 

 tilizer all at one tune, just before the spring plowing, 

 while some make two or three applications a year. 

 California soils are usually high hi potassium, and 

 wherever the humus is high, this element is hardly 

 needed. In many cases in which the soil is deep, rich 

 and high in humus, an annual application of ten to 

 fifteen pounds of ground phosphate rock to a tree, 

 together with the vetch crop and five tons of alfalfa or 

 bean straw to the acre every alternate year will be a 

 satisfactory program. Orange trees are very suscep- 

 tible to alkali. Where the soil contains .2 of 1 per cent 

 of total salts, the trees begin to decline. A total salt- 

 content of less than .1 of 1 per cent is usually considered 

 safe. These figures will vary somewhat, however, accord- 

 ing to the proportion of the different salts, which, 

 taken together, are known as "alkali," some of which 

 (such as sodium carbonate) are very injurious. 



Irrigation. 



On none of the citrous areas of California is the rain- 

 fall sufficient. Irrigation is practised in every orchard. 



For the most part, water is taken out of streams near 

 the upper headwaters and conveyed by gravity through 

 cement canals sometimes for hundreds of miles to 

 the citrous orchards. Often the descending water 

 generates electrical energy to be used in pumping 

 additional supplies from wells. The water is distributed 

 through steel or concrete pipe-lines and delivered at 

 the upper end of the furrows. Usually the grower buys 

 the water-right with the land and is assessed annually 

 for the upkeep of the system serving him. The keys 

 to the water gates are kept by a water-boss or "zanjero" 

 who measures out to each grower his proper allot- 

 ment. The amount of water required varies with the 

 character of the soil and the age of the trees. Full- 

 grown bearing trees require from 1 ordinary miner's 

 inch continuous flow to 10 acres up to as much as an 

 inch to 3 acres, depending on the rainfall and whether 

 the soil is a heavy clay or an open sand or gravel. An 

 irrigation is given every month or six weeks during the 

 summer and less often in winter, according to the rains. 

 In heavy soils, the water is run for three or four days at 

 each irrigation hi very small streams through four deep 

 furrows to each tree row. The water is cut off when 

 tests with a soil-tube show the soil to be soaked 5 feet 

 deep. In very light porous soils, it is necessary to throw 

 up ridges each way, leaving each tree in the center of a 

 large basin. These basins are filled quickly with a large 

 stream. It is only by the use of large, rapid streams that 

 water may be conveyed across and distributed over 

 such open and porous soils. 



The common or spring vetch (Vicia saliva) is very 

 commonly grown as a green-manure crop in southern 

 California. It is planted in September and turned under 

 in February before the trees start the spring growth. 

 The seeds are large and germinate well and the vines 

 suffer less from the trampling incident to harvest than 

 some other green-manure plants. Canada field peas, 

 Tangier peas, bur clover, fenugreek, and sour clover 

 (Melilotus indica) are occasionally used in place of the 

 vetch. In northern California, bur clover volunteers 

 satisfactorily and is commonly used. Summer green- 

 manure crops, such as cowpeas, are coming into use 

 wherever there is sufficient cheap water available to 

 supply both the trees and the peas during the dry 

 hot months. 



Pruning. 



Orange trees are pruned somewhat differently 

 according to the variety. The young Washington 

 Navel tree should not be pruned for the first two or 

 three years after being headed and set in the orchard. 

 Especially if budded from the best type of wood, it 

 may be depended upon to form a good head by itself. 

 Suckers should of course be removed whenever they 

 appear. The Valencia is a more rampant grower, and 

 the young upright shoots are apt to grow too long 

 before branching. They should be pinched back. In 

 pruning old trees, the following rules are thought to 

 embody the best practice: Remove suckers whenever 

 and wherever they appear. Remove the too vigorous 

 vertical shoots which tend to produce coarse fruit. 

 Remove old brush of waning vitality. Thin the tops 

 and, to some extent, the sides so as to allow proper 

 airing and lighting of the interior foliage, thus encour- 

 aging the production of high quality, inside fruit. 

 Remove all dead twigs from the fruiting brush. Navel 

 trees rarely need propping, while Valencia trees, unless 

 the limbs are kept short and stout by pinching, are apt 

 to require a great deal of propping. 



Harvesting. 



California oranges are harvested the year round, the 

 Navels, from November 1 to May 1; seedlings and 

 miscellaneous varieties during May; and the Valencias, 

 from June 1 to November 1, thus overlapping the next 

 Navel crop. A ripe Navel will remain in prime con- 



