56 



AGRICULTURE OF MAINE. 



having stated recently that they contain 98 per cent water, and 

 hence have no need for any actual fertility or plant food. It is 

 true that apples actually are about 84 1-2 per cent water on the 

 average, but it is also true that in the remaining 15 1-2 per cent 

 of solids much actual plant food is contained. 



The real amount of this food can be approximated chemi- 

 cally by determining the average composition of apple wood, 

 leaves, and fruit, and by applying these figures to what may be 

 considered good annual amounts of these products. This we 

 have done both for apples and for a 25-bushel crop of wheat, 

 with the results shown in Table L The annual weights for 

 apples are based on a yearly production of 100 pounds each 

 of wood and leaves, and of 14 bushels of apples per mature 

 tree. All these amounts are distinctly less than those actually 

 observed and reported, but inasmuch as they give an annual 

 yield of 490 bushels per acre of 35 trees they are considered 

 sufficient for the present purpose. 



TABLE I.— THE RELATIVE PLANT-FOOD DRAFT OF WHEAT AND APPLES. 

 (In Pounds per Acre Annually, Based on American and German Averages.) 



Annual Weights. 



Wheat 

 grain 

 Lbs. 

 1500 



Wheat 

 (Total) 



Lbs. 



4200 



Wood 



Lbs. 

 3500 



Leaves 



Lbs. 

 3500 



Fruit 



Lbs. 

 24500 



.\pple 



(Total) 



Lbs. 



31500 



Nitrogen (N) 



Phos. Acid (P2O5). 

 Potash (K2O) . . . . 



Lime (CaO) 



Magnesia (MgO) . . 

 Iron (FeO) 



53.1 

 15.3 

 64.0 

 61.6 

 16.7 

 2.8 



This table shows that in total food draft, the apples exceed 

 the 25-bushel wheat crop in every constituent except phos- 

 phoric acid, and in it they fall behind only by half a pound. 

 Notwithstanding this fact, apple trees are usually able to main- 

 tain themselves much better and longer than wheat. This is 

 doubtless largely because of their much longer season of root- 

 activity, their more natural demands,* the annual return of 

 most of the plant food in their leaves, and their ability to furnish 



*This is especially marked in the case of the fruit as compared with 

 the demands of the grain in wheat. For further discussion, see article 

 by the writer in the Annual Report of the Pennsylvania Experiment 

 Station for 1910-11, pages 447 to 449. 



