120 THE CONNECTICUT POMOLOGICAL SOCIETY 



trees takes from the soil in a year, and how much of this 

 is taken away from the land in fruit and leaves. This can- 

 not be directly and fully answered, for the data are lack- 

 ing. Let us see what we have. We have a single esti- 

 mate of the quantity of plant-food removed in a crop of 

 peaches as determined several years ago at our station. 

 Reckoning 130 trees to the acre, and three baskets to the 

 tree, as an average yield from orchards five years planted, 

 we found that about 20 pounds of nitrogen, 22 of potash, 

 four of phosphoric acid and only one of lime were taken 

 from an acre of peach orchard in the fruit. By the way, 

 the pulp of the peach contains, by far, the larger part of 

 the nitrogen and mineral matters. The stones and seeds 

 carry only one-fourth of the nitrogen and one-tenth of the 

 ash elements. 



The composition of apples, and very likely that of pears, 

 is not very different from that of peaches, though pound for 

 pound of fruit, apples take more mineral matter from the 

 soil than peaches. The leaves, too, contain, while growing, 

 large quantities of mineral matter, and carry off a part of 

 this when they fall, not the whole of it, by any means. It 

 is a well-established fact that, during the summer, the tree 

 withdraws these things from the leaf into the stem. Thus 

 it has been shown that the leaves of the peach contain the 

 highest percentage of nitrogen, phosphoric acid and potash 

 in May, and the percentage steadily decreases through the 

 season. The largest total amount is found in July, and 

 then decreases till the leaves fall. In some tests of oak 

 and chestnut leaves years ago, I found that green oak leaves 

 lost between one-third and one-half of the per cent of nitro- 

 gen in their dry matter between the time they began to 

 fade and the time they were dead or falling — less than one 

 month. That is, on October 16 the leaves contained 1.93 

 per cent of nitrogen, but November 13 they had onl}' .77. 

 The dry substance of the leaves in the same time lost two- 

 thirds of the percentage of potash, and one-half the per- 

 centage of phosphoric acid, while the lime remained, and 

 did not flow back into the tree trunk. For these reasons, I 

 believe, estimates of the exhaustion of soil calculated from 

 the analyses of leaves gathered before they fall, are likely to 



