8 FUNDAMENTALS OF FRUIT PRODUCTION 



conserving practices. Experience may be a still better guide but only 

 to the extent that it gives ability to judge local conditions and so permits 

 a more accurate interpretation and application of general principles. 



Some measure of the way these principles apply to concrete cases 

 may be obtained from the statement that it has been found practicable 

 to use irrigation water amounting to about 30 acre-inches for mature 

 peach trees on some of the gravelly loams of Utah and 40 acre-inches on 

 full bearing apple orchards on sandy loam in Idaho where rainfall aver- 

 aged 10 or less inches per year. On the other hand, heavy crops of sweet 

 cherries, prunes and apricots are obtained without irrigation from 

 orchards on a light sandy loam at The Dalles, Ore., with an average 

 annual rainfall of 16 or 17 inches. 



Some years ago 16 or 18 inches of rainfall annually was generally 

 considered sufficient for the production of deciduous fruits in California, 

 but experience has demonstrated that the percentage of this amount 

 that is actually left for the trees after run-off, seepage and evaporation 

 is not adequate for the average orchard with the trees spaced the usual 

 distances. As a matter of fact there is a growing belief that even a 

 rainfall of 30 inches in California should be supplemented by provision 

 for irrigation to take care of occasional emergencies. i" 



Planting Distances Related to Moisture Supply. — Application of the 

 principles just pointed out to particular fruits and particular locations 

 should be the main deciding factor in determining distance of planting for 

 orchard fruits, for water supply is most frequently the liqiiting factor in 

 this connection even though the grower seldom realizes it at the time of 

 setting. This is contrary, in the way it often works out, to the frequently 

 repeated statement that trees can be planted more closely in a "poor" 

 than in a "good" soil. If the soil is "poor" because it is shallow or of 

 poor water-holding capacity unproductiveness will only be increased by 

 closer spacing. In soils that are both fertile and well-watered, planting 

 distance should be governed by the size of the plants and the growing 

 habit. If they are infertile and well-watered, again planting distance 

 should be determined by size of plant and growing habit, and the fertility 

 question solved through the proper use of fertilizers. If moisture is the 

 limiting factor, regardless of the relative productivity of the land, spacing 

 should be determined largely by moisture requirements, though due 

 attention should be given to growth characteristics. 



A notable instance of the intelligent and successful application of these 

 principles to the question of planting distance is found in some of the olive 

 orchards of northern Africa. Though the usual planting distance for this fruit 

 in irrigated sections, or in regions of ample rainfall is 18 to 22 feet, near Sfax in 

 Tunis the trees are planted 60 to 80 feet apart, making only 7 or 8 to the 

 acre. This arrangement makes possible a profitable dry-land industry without 

 irrigation, though the mean annual rainfall is only 9.3 inches and though there 



