CHAPTER XV 

 IRRIGATION OF FRUIT TREES AND VINES 



Whether fruit shall be grown with irrigation or not is a local and 

 specific question, and it must be answered with due regard for several 

 conditions, among which are: First, the minimum local rainfall; 

 second, the depth and character of the soil and subsoil; third, the 

 situation and environment of the ground on which the fruit is to be 

 grown ; fourth, the kind of fruit which it is desired to produce. 



These conditions are all correlated, and a knowledge of them all is 

 necessary to an intelligent decision as to correct practice in any given 

 locality. For example, the amount of rainfall which is adequate in one 

 locality, or in one situation, even, may be quite insufficient in another, 

 because, first, one soil may be deep and fairly retentive, into which 

 roots can penetrate and find abundant moisture; second, another soil 

 may have sufficient depth, but be so porous as to lose its moisture by 

 evaporation, or so leachy as to lose it by drainage; third, still another 

 may be shallow, and quickly dried out under a fervid sun, or quickly 

 drained by reason of a sloping substratum of rock or hardpan, while 

 another similar soil, differently situated, may receive abundant moisture 

 from the drainage of the slope above it ; fourth, possibly in all the soils 

 cited there might be adequate moisture for deciduous fruits, but citrus 

 fruits would require irrigation; or enough for young, but not for 

 bearing trees. 



Thus it appears that even to decide whether a location has sufficient 

 rainfall for the growth of fruit without irrigation, one must pass 

 judgment upon all the conditions first mentioned. It is hardly worth 

 while, then, to discuss such a topic upon theoretical grounds, or to 

 attempt to answer the general question, Shall irrigation be employed 

 in the growth of fruit ? The true guide is enlightened local experience, 

 and the true test is the growth of the tree and the excellence of its 

 fruit. So long as the grower is able to secure every year a generous 

 amount of good-sized and excellent fruit by natural rainfall, he need 

 concern himself very little about irrigation; if his tree shows distress, 

 and his fruit, even when properly thinned out, is not up to market 

 standards every year, he may do well to provide himself with irriga- 

 tion facilities, either for constant use or to supplement rainfall when 

 it is occasionally deficient. 



Of course it is not commended that the grower wait until the tree 

 shows signs of distress before applying water. This is a very bad plan 

 of proceeding, but the visible language of the tree is mentioned as indi- 

 cating that the tree needs help, either at regular intervals or occasion- 

 ally, and after such a warning the grower should be able to tell by 

 examination of the soil and by study of the local rainfall record when 

 this need will occur, and apply his water in advance of the need. 



Recent experience has enabled fruit growers in all parts of Cali- 

 fornia to arrive at a truer conception of the relation of irrigation to the 

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