206 The Principles of Fruit-growing. 
of twenty-one pounds nitrogen, three pounds phos- 
phorie acid, twenty-six pounds potash.” 
“As a clearer comprehension is had by comparing 
unfamiliar things with familiar things, a table follows 
which gives in brief the soil exhaustion which is 
likely to oceur from a continuous twenty-year wheat 
production. Here, again, an average yield has been 
assumed which, while approximately correct for New 
York, may be wide of the mark in some states where 
the average yield of wheat falls to eight or ten bush- 
els per acre. 
“The following tables show the amounts and 
values of the fertilizing ingredients removed by wheat 
(grain and straw) in twenty years’ continuous crop- 
ping, assuming an average yield of fifteen bushels per 
acre and seven pounds of straw to three pounds of 
graln: 
“COMPOSITION CF WHEAT AND STRAW. 
Water, Nitrogen, Phos. acid, Potash, 
per cent. per cent. per cent. per cent. 
CPB coy wees GREY 8X 14.75 2.36 89 -61 
BUPOW ocak die e mag 0% 12.56 -559 12 -51 
“AMOUNTS AND VALUE OF PLANT-FOOD REMOVED IN ONE YEAR 
AND IN TWENTY YEARS. 
Nitrogen, Phos,acid, Potash, Total 
Ibs. lbs. lbs. value. 
Grain, 1 year. co. ans 21.24 8.01 5.49 $3.99 
Grain, 20 years...... 424.80 160.20 109.80 79.86 
Straw, l year ....... 11.74 2.52 10.71 242 
Straw, 20 years...... 234.78 50.40 214.20 48.37 
Total value in wheat, grain and straw for 20 years. $128.23 
Total value in apple, fruit and leaves for 20 years.. 207.45 
“The above table shows that the orchard requires, 
