78 FUNDAMENTALS OF FRUIT PRODUCTION 



"The character of the autumn, particularly with reference to rainfall, deter- 

 mines in large measure the size and the quahty of the fruit crop of the following 

 year. An interesting example of this relation is apparent in the 1919 deciduous 

 fruit crop, which is the largest of this kind ever grown in California. During 

 September, 1918, the heaviest rains recorded in a month of September in California 

 during 69 years of record were general throughout the central portions of the 

 State."ioi 



Regularity of bearing, as is pointed out later, is probably more closely 

 associated with and dependent upon, natural flowering habit and the 

 nutritive conditions within the plant than upon soil moisture. However, 

 the following quotation from a report on a series of orchard soil experi- 

 ments in Pennsylvania suggests the wisdom of looking after the moisture 

 supply when it is more or less under control: "In two treatments, the 

 yields of Baldwin and Spy have remained almost constantly between 

 400 and 700 bushels per acre annually for the past 7 years, while marked 

 fluctuations in yield were occurring in adjacent plots under other treat- 

 ments. The essential features of the former treatments have been 

 an ample food and moisture supply, the absence of excessive yields in 

 any one year, and undisturbed root system. "^^^ 



In most of the cases cited it is impossible to differentiate between the 

 direct influence upon the plant of water from the rains of the preceding 

 summer and fall stored over winter in the soil and what has been termed 

 indirect effects through immediately influencing leaf fall and food storage. 

 To the grower it is the combined effect that is important. The facts 

 presented carry a particularly significant lesson for the grower in an 

 irrigated section where fall and winter rains cannot be depended on, but 

 irrigation water is available. They suggest also that the tree that 

 matures its crop early in the season, whether a cherry, apricot, peach or 

 summer apple, has as real, though perhaps not as great a need of late 

 summer, fall and winter irrigation as one maturing its crop in October. 



Influence of Atmospheric Moisture on Growth. — It is difficult in 

 many cases to distinguish clearly between the effects of soil moisture and 

 of atmospheric humidity on the plant. Atmospheric humidity has an 

 influence on plant development independent and distinct from that of 

 soil moisture, though it often happens that both influences tend in the 

 same general direction. 



In General. — Under average outdoor growing conditions abundant 

 soil moisture is likely to be accompanied by relatively high humidity and 

 low soil moisture by a dry atmosphere. In practice, therefore, these two 

 factors of environment are more or less interdependent. The relation of 

 the two is brought out by data presented in Table 37. In a general way 

 it may be stated that extreme moisture, either of soil or of air, hinders 

 the differentiation of tissues while dryness accentuates the develop- 

 ment of strengthening and conducting tissues. Examples of these 



