THE APPLICATION OF NITROGEN-CARRYING FERTILIZERS 215 



increases in vegetative growth, figured in the same way, length of terminal 

 shoots being taken as a measure of vegetative vigor. Both lines represent 

 10-year averages of a number of experiments on mature apple trees 

 growing under various soil conditions. Though these curves show slight 

 irregularities, those for increases in growth take the same general direc- 

 tion as those for increases in yield. In other words, as vegetative growth 

 has increased, yields have increased, but yields have increased much more 

 rapidly than vegetative growth. This latter fact would seem to prove 

 beyond all question not only that increased vegetative growth due to 

 fertilization is not generally antagonistic to heavier fruit production, but 

 that within limits it actually encourages heavier fruiting. Data recently 

 presented for apple tree growth and yields in Delaware lead to the same 

 general conclusion. ^"^^ Graphs shown in Fig. 26, made from 4-year 

 averages for increases in peach yields in West Virginia through fertiliza- 

 tion, show the same relationship between vegetative growth and yield. 

 Here, though yields have not quite kept pace with the increased vegeta- 

 tive growth, the conclusion is obvious that in the peach increased wood 

 growth is associated with increased fruit production. 



The same graphs showing the general relationship between vegetative 

 growth and yield also throw some light on the way in which the fertilizers 

 have increased production. Under the conditions of these tests about 

 half of the increased yield was due to the greater wood growth; in other 

 words, to the effect of the fertilizer in producing additional fruit spurs and 

 fruit-bud-bearing shoots. The other half oi the increase was due appar- 

 ently to the greater activity of the old spurs. Presumably increased 

 yield was not obtained in the New York and New Hampshire experiments 

 to which reference has been made because the trees' nutritive require- 

 ments for new wood growth were fully met by the supply already avail- 

 able in the soil and because they were already producing heavy crops. 

 That decreased yield often accompanies increased vegetative growth 

 following the use of nitrogenous fertilizers is indicated by results with 

 strawberries in Missouri ^^ and with red raspberries in New York." 



Influence of Nitrogen on Composition and on Season of Maturity. — 

 The composition of various plant tissues, especially in so far as their 

 mineral constituents are concerned, has been shown to be influenced 

 considerably by the character of the soil in which they grow. Their 

 composition would be expected, therefore, to show the influence of 

 fertilizer application. Some interesting experimental data on this 

 question have been obtained with rj'^e, buckwheat and certain other crops. 

 These crop plants were grown in what were considered normal media and 

 in media possessing excessive amounts of certain nutrients. The following 

 statements from the report on these experiments may be quoted here:^^ 

 "In general it appears as if the nutrients actually required for normal 

 growth of the crops, when there are plenty of other ingredients to furnish 



