Manures and Manuring 



143 



TOTAL WEIGHT AND CONTENTS OF ONE WAGNER APPLE TREE, THIRTEEN 

 YEARS OLD, AND OF THIRTY-FIVE SIMILAR TREES TO THE ACRE 



At the end of twenty years (the Apple trees being then thirty-three 

 years of age) it was computed that the amount of nitrogen, phosphoric 

 acid, and potash taken from the soil during the period of trial was as 

 follows: 



These quantities are much less per acre per annum than those already 

 given above. They serve, however, to indicate the small amount of food 

 exhaustion that takes place, and incidentally the quantities of nitrogen, 

 phosphoric acid, and potash that might have to be supplied to maintain 

 the equilibrium of available foods in the soil. Assuming the figures to 

 be fairly accurate, it would appear that the fallen leaves, if dug into the 

 ground during the winter months, would supply, when rotted, about half 

 che entire quantity of food taken out during the year, as shown, thus: 



The quantities of nitrates, phosphates, and potash taken out of an acre 



