HORTICULTURE 273 



nearly as may be possible. The tree must not stand deeper in the 

 soil than it did in the nursery. Many trees are killed or stunted by 

 being planted too deep. Fill in the soil gradually and press it about 

 the roots, but not too tightly, unless it be a very light soil. If water 

 is available, it is well to settle the soil about the roots by its use, 

 but in this case, tramping must not be done on the wet soil. 



Cutting Back the Top of the Tree. Cutting back is necessary, 

 unless the tree has been removed with a large ball of earth. It has 

 lost a large part of its root system in being moved and can not 

 support the whole top. This pruning may be done either before 

 or after planting. The main stem or leader of the tree should be 

 cut back to a bud or branch, aoout 2 1 / feet to 3 feet from the ground 

 and the side branches should all be cut back, more or less severely, 

 according to the injury which has been sustained by the root 

 system. 



Tillage. The orange requires good, clean tillage. If weeds 

 and grass are allowed to occupy the ground during the period of 

 growth the grove will suffer. In the matter of plowing there is a 

 difference of opinion. Most orange orchards, however, are plowed 

 at least once a year. Those that are not plowed are constantly stirred 

 to almost as great a depth by the use of very effective harrows and 

 cultivators. The harrow or cultivator should be used often enough 

 to keep the surface soil loose. In California it has been found a dis- 

 tinct advantage to vary the depth of tillage from year to year, thus 

 avoiding what is known as "plow sole," or "hard pan," a hard and 

 impervious layer of soil which sometimes forms when the soil is con- 

 tinuously tilled to the same depth. 



Irrigation. All citrus trees require liberal amounts of water. 

 The exact quantity necesary can not be stated, since it will vary 

 with the character of the soil, the distribution of the rainfall, and 

 the care taken in its conservation in the soil. In California it may 

 be said in general to vary from 24 to 44 inches in depth per year, 

 including precipitation and irrigation, but it is carefully applied 

 and conserved so as to make the very best use of it. These figures 

 must be regarded not as a prescription, but simply as a standard of 

 measurement for varying conditions. The number of applications 

 into which a given amount of water will be divided also varies. In 

 California the citrus orchards are irrigated from three to eight times 

 per year. The best practice in these matters can be determined 

 only by the grower himself after study of his local conditions. 



Method of Application. Perhaps the simplest method for the 

 application of irrigation water is that known as the "furrow sys- 

 tem," which consists in plowing a number of furrows in the spaces 

 between the rows of trees and in turning the water into these from 

 the more permanent ditches or flumes which run along the ends of 

 the rows. 



Tillage should follow irrigation as soon as the land is dry 

 enough to admit of it. 



Fertilization. Citrus trees require the liberal use of fertilizers, 

 unless the soil be unusually rich. Few fruit trees show such marked 



