214 



FUNDAMENTALS OF FRUIT PRODUCTION 



per acre to last mature apple trees 183 years, of phosphoric acid, 295 

 years, of potash, 713 years. "^^ Evidently amounts of these nutrients 

 sufficient for the trees' growth and production were being made available 

 year after year by various natural agencies. 'The second of the two 

 investigators, though not reporting on the total nitrogen supply of the 

 soil, presents data to show that the clean cultivation-cover crop method 

 of management made available each season plenty of nitrogen, though 

 after some years there was some evidence that nitrogen applications in 

 the near future would increase yields. ^"^^ In the presence of abundant 

 supplies additional applications gave no increased yields worth mention- 

 ing. Interesting in this particular connection are data presented in 

 Table 73 showing the effects of various amounts of nitrogen-carrying 

 fertilizers on yield of pears. The trees were yielding well without 



Table 73. — Effects of Various Amounts of Nitrogen-carrying Fertilizers 

 ON Yield of Pears 



{After Reimer^^*) 



fertilizer applications but when small amounts of quickly available 

 nitrogen were applied they at once responded, production apparently 

 reaching a maximum (thinning being practiced) for the size of trees in 

 question. Applications of larger amounts of fertilizer under these 

 conditions resulted in no greater yield. If larger amounts are available 

 they are not taken up or if taken up they are not used in increased fruit 

 production. It is economical for the grower to apply only such fertilizers 

 in such amounts as the tree can use with profit to himself. 



The Correlation Between Vegetative Growth and Yield. — Bearing 

 directly on the question of the influence of fertilizers, particularly nitrog- 

 enous fertilizers, on yield and also on that much disputed question as to 

 whether vegetative growth and fruit production are antagonistic tenden- 

 cies, are the graphs shown in Figs. 25 and 26, plotted from data on apple 

 yields and growth as influenced by fertilizers in Pennsylvania and from 

 data on peach yields and growth in West Virginia. The solid lines in 

 Fig. 25 represent increase in yield (in percentages) resulting from the 

 use of various fertilizer combinations. The dash-dot lines represent 



