144 



FUNDAMENTALS OF FRUIT PRODUCTION 



removed by the dissolving action of rain. This is true of many fruit trees, as 

 Table 30 shows. ^^^ This relation does not hold for young trees just in bearing. 

 That more phosphorus is lost in the crop than with the leaves of mature trees 

 may be attributed to several factors. As has been emphasized, only one-tenth 



Table 30. — Pounds of Phosphorus in Parts of a Full Grown Tree'^o 



to one-fifteenth as much phosphorus as nitrogen is left in the leaf, but the fruit 

 contains one-fifth as much phosphorus as nitrogen. This in turn may be cor- 

 related with the finding that the phosphorus content of leaves on peach trees 

 in heavy bearing is less than that of the leaves on trees bearing a small crop.^*'^ 



Table 31. — Phosphorus Content of Peach Leaves in Bearing and Non-bearing 



Years'" 

 (Percentage of dry weight) 



First four years . 30 



Five years of bearing . 24 



1904 (no crop) 0.29 



The data in Table 29 suggest that this may hold for the apple as well as the peach. 

 Table 32 gives the phosphorus content of various fruits in absolute amounts. It 

 is present in seeds in greater amounts. 



Table 32. — Pounds of Phosphorus in 1,000 Pounds of Fresh Fruit^" 



Almonds 0.45 



Apricots . 29 



Apples 0.14 



Bananas . 07 



Cherries 0.31 



Chestnuts 0.52 



Figs 0.38 



Grapes 0.05 



Lemons . 25 



Olives 0.55 



Oranges 0.23 



Peaches . 37 



Pears 0.15 



French prunes 0.30 



Plums 0.33 



Walnuts 0.65 



POTASSIUM 



Though the history of potassium in a fruit tree like the apple is in 

 many respects similar to that of phosphorus, there are important 

 differences. 



S3mthesis, Translocation and Use of Potassium-containing Com- 

 pounds. — It is not known where potassium is elaborated and there is no 

 evidence to show that the inorganic potassium taken from the soil by 

 the roots is combined in organic form in the leaves to any greater extent 

 than in any other part of the plant. In just what form of organic com- 

 bination potassium is necessary for the proper activity of the plant is also 



