THE APPLICATION OF NITROGEN-CARRYING FERTILIZERS 211 



Virginia on the influence of fertilizer treatments on fruit size, especially 

 as increases in size are correlated with increased or decreased vegetative 

 growth and with increased or decreased yield. In some of the cases 

 reported by Stewart, but not shown in the graphs, fertilizer applications 

 were accompanied by decreased size of fruit. In commenting on his 



120 



90 



80 



60 



50 



.-^0 



20 



^/^ata Stewart^^* says: "In the 

 matter of fruit size, some benefits 

 are indicated . . . but they have 

 proved less as a rule than is com- 

 monly supposed. Manure has 

 naturally been most consistent in 

 increasing the average size of the 

 fruit, probably chiefly on account 

 of its mulching effect . . .in 

 general we believe that the plant 

 food influence will always be sec- 

 ondary to moisture conservation 

 and proper thinning, wherever 

 greater fruit size is desired." 

 Alderman^ in his fertilizer work 

 with peaches found but little in- 

 crease in size from the use of 

 fertilizers, nitrogen in combination 

 with potash showing slight gains. 

 At the Missouri Station it was 

 found that in some cases the fer- 

 tilization of peaches with nitrogen "i-O 

 was attended by a marked decrease Fig. 26.— Response of peach trees to 



„ „ •- ,1 • 1 fertilizer treatments, showing increases or 



m Size Ot truit, this decrease some- decreases in yield and fruit setting accom- 



times amounting to as much as 40 panying increased shoot growth. (Plotted 



, „„„ from data given by Stewart.''*) 



per cent. 202 



The explanation of the frequent failure of the fruit from fertilized 

 trees to show an increase in size over that from unfertilized trees and of 

 the occasional decreases in size lies in the increased wood growth and 

 leaf area of the plants and consequently in their increased demand for 

 water. As this increase in leaf surface may sometimes amount to over 

 100 per cent, it is easy to understand how water may become a limiting 

 factor. Especially is this true when it is remembered that the osmotic 

 concentration of the leaves is greater than that of the developing or 

 maturing fruits and hence in times of stress the fruits may actually lose 

 water to the leaves which supplies their transpiration requirements 

 and keeps them turgid. ^^ This, however, is an indirect effect of nitrog- 

 enous fertilizers on size of fruit, occasionally important in orchard 

 practice and suggesting that increased attention should be given to 



