Feeding the Plantation 131 



the dormant season, from autumn till early spring. In 

 mature plantations, it is best to apply manure to the entire 

 area rather than to pile it close to the trees or vines. 

 Plowed under in early spring, the barn manures should 

 have a marked effect in ameliorating the land and improv- 

 ing the thrift and stamina of the plantation. 



CHEMICAL FERTILIZERS 



Presumably, fruits profit by the application of ferti- 

 lizer to the land because they use the kinds of materials 

 that fertilizers contain. The standard computations of 

 Roberts, from analyses, show the following values of 

 nitrogen, phosphoric acid and potash taken from an acre 

 by apple trees (the trees 35 feet apart) in twenty years, 

 counting in ten crops of fruit: 



Value 



Total in fruit for twenty years $147 00 



Total in leaves for twenty years 160 51 



Total in wood for life of tree 70 00 



Grand total $377 51 



"The value of nitrogen, etc., in any given case is so 

 indefinite and variable that stress should not be laid on 

 values as given, but on the total amounts of plant-food 

 used by the orchard, as follows: 



"The total amount of nitrogen, exclusive of that used 

 in the growth of the trees, is 1,336.8 pounds, of phosphoric 

 acid 310 pounds, and of potash 1,895.4 pounds. To restore 

 the potash alone, as above and that used by the growth 

 of the tree, it would require 21.69 tons of high-grade ashes 

 containing 5 per cent of potash. To restore the nitrogen 

 as above would require 16.19 tons per acre of a commercial 

 fertilizer containing 5 per cent of nitrogen. 



