RESPONSE OF FRUIT PLANTS TO CONDITIONS OF SOIL 71 



If this second growth comes fairly early so that the new tissues have 

 time to harden and mature properly before winter freezing, little harm 

 may result, but often when it comes late in the season the tissues do not 

 mature thoroughly and serious winter killing or winter injury follows. 

 It is doubtful if, irrespective of susceptibility to winter injury, much 

 "second growth" is desirable in sections with more or less severe winter 

 weather, for there is reason to believe that the tissues are formed at the 

 expense of stored materials that could be used perhaps to better 

 advantage the following spring and summer. 



Influence of Water Supply on the Development of Fruit. — The 

 influence of soil moisture on the development of the fruit is no less 

 important than its influence on vegetative growth. 



Size. — The largest fruits are found on the best watered trees and 

 there is abundant experimental data to show the effect of soil moisture 

 upon fruit size. Thus Hedrick,^^ who found his tillage plots to contain 

 more soil moisture than his sod-mulch plots reports the average weight 

 of apples from the cultivated trees to be 7.04 ounces while the average 

 weight of those growing in sod was only 5.01 ounces. This difference 

 of 40 per cent, was presumably due mainly to the difference in moisture 

 supply and accounts in large part for the difference in yield between 

 the two plots, which averaged 36 barrels per acre. 



In the discussion of the influence of soil moisture upon vegetative 

 growth it is pointed out that new shoot growth and new leaves are made 

 early in the season and it may be only during a comparatively short 

 period in spring and early summer that this growth is influenced in amount 

 by soil moisture. On the other hand, most of the growth of the fruit 

 tissues takes place after midseason and therefore it is reasonable 

 to believe that soil moisture exerts its greatest influence on their 

 development during the last half of the summer and during the autumn. 

 That this is actually the case is indicated clearly by a number of irriga- 

 tion experiments. In Idaho, irrigation of winter apples before July 10 

 had very little influence on their size, though irrigation after that date 

 had a very decided influence. ^^^ Batchelor^^ in reporting upon the 

 results of irrigation experiments with peaches, states: "No amount of 

 water applied early in the season to a crop of peaches on a gravelly soil 

 will compensate for the lack of water during the month before harvest. 

 ... A larger amount of water is evidently required if the irrigation is 

 deferred until late in the season than in case the water is applied throughout 

 a longer period of growth." There is ample evidence to show that for 

 the production of fruits of large size the trees should be well supplied 

 with available soil moisture throughout their growing season. Through 

 measurements of apples made at intervals of two weeks throughout the 

 season it has been found that size increased steadily from the time of 

 setting to maturity. ^^^ This suggests the advisability of cultural treat- 

 ments to promote a steady growth. That there is a limit, however, 



