AREA OF POSSIBLE DRY-LAND OLIVE CULTURE. 41 



AREA LIMITED BY RAINFALL. 



Taking up the consideration of rainfall, the industry must be con- 

 sidered from a different standpoint from that in which olive growing 

 has been viewed in this country in the past. The usual planting dis- 

 tance has been from 20 to 24 feet. With abundant water the trees 

 might prosper and produce remunerative crops with this area to draw 

 from. Wlien dependent upon local rainfall they have shown signs 

 of failure. 



In the valuable pamphlet on olive culture entitled "Investigation 

 Made by the State Board of Horticulture of the California Olive 

 Industry, Report to Governor Gage," 1900, page 29, is found a very 

 significant discussion of the water problem by the Hon. Frank A. 

 Kimball, the substance of which is as follows: Olive trees set at the 

 ordinary orchard distance in this region, usually about 116 trees to 

 the acre, gave during their earlier years very excellent results with- 

 out irrigation. The growth was vigorous and the fruit large and 

 fine. 



Mr. Kimball gives a graphic account of their condition a few years 

 later, as follows: 



The trees on becoming large required the necessary moisture to develop their growth, 

 which had now assumed immense proportions. The soil could not furnish the require- 

 ments of the trees, and in the summer they lost the larger portion of their leaves. They 

 remained in this semidormant condition until the rainy season set in or moisture 

 from the soil began to rise. Most of the fruit dropped, and what did not fall did not 

 attain a size suitable for picking. This condition of affairs continued until the growers 

 resolved to apply water. After a season or more of demonstration they found irri- 

 gation to be one of the essential means through which a crop of fruit can be assured. 



The reason why we do not get olives is, the trees are starved, if want of water can 

 be called starvation. For lack of water the soil can not furnish the material from which 

 the olive is made. 



The idea that the olive trees need a certain minimum volume of 

 water for the performance of their physiological work is a fundamental 

 one, but it does not seem to have occurred to these growers that by 

 reducing the number of trees to the acre, thereby giving to each tree 

 a sufficient area to afford the needed moisture, the same results 

 might be secured as by irrigation. The olive has shown its ability to 

 send out a root system that will secure the needed moisture from the 

 larger area of soil and maintain a high productiveness. This has 

 been shown by Mr. T. H. Kearney's study of the dry-land culture of 

 the olive in Tunis, now accessible in Bulletin 125 of the Bureaii of 

 Plant Industry. From this publication we learn that a great olive-oil 

 industry is carried on in Africa on lands receiving normally only 

 from 9.3 to 15 inches of rainfall annually, while several good cro})s 

 were produced during a period of seven years when the rainfall 

 averaged only 6 inches, according to the French records. 



192 



