INJUEIOUS EFFECT OF LEAF MOLD. 25 



On February 20, 1909, 25 blueberry seedlings were potted in 3-inch 

 earthenware pots in a mixture consisting of eight parts by bulk of 

 the leaf mold just described, one part of clean sand, and one part of 

 clayey loam derived from rotted grass turf. Fifty other plants were 

 potted in the same manner except that in place of the mold a peat 

 was used known from earlier experiments to be well suited to blue- 

 berry growing. The plants were kept in the greenhouse until warm 

 weather when they were placed outdoors. All were given the same 

 treatment, a treatment favorable to good growth. 



It had been expected that the plants in the leaf mold would show a 

 vigorous growth, and it was hoped that the mold might prove even 

 superior to the peat for blueberry soil mixtures. The experiment as 

 it progressed, however, showed that such was not the case. The leaf 

 mold proved to be not merely not a good soil for blueberries but an 

 extremely poor one, as the following particulars will show. 



A\Tien the plants were potted they averaged about 2^ inches in 

 height. On May 29 the peat-soil plants had an average height of 7{ 

 inches, while the leaf -mold plants averaged 4j inches. At this time 

 the herbage of the leaf -mold plants was decidedly purpled and yel- 

 lowish, a coloration which they had taken on soon after they were 

 potted and from which they never fully recovered. At the end of the 

 season, after the leaves were shed, the peat-soil plants averaged 13;^ 

 inches in height and the leaf-mold plants Tf inches. On November 29, 

 1909, five average plants from each lot were cut otf at the surface of 

 the ground and weighed. The weight of the stems from the leaf -mold 

 plants was less than one-fifth that from the plants in the good blue- 

 berry soil. 



When these plants were removed from their original seed bed to 

 be transplanted to the 3-inch pots, such of the original soil as clung 

 to their roots Avas not shaken off. It is believed that the leaf-mold 

 plants fed in part on this original soil in making their new growth, 

 and that without it they would have shown still less increase in 

 height than they did. The peat-soil plants, moreover, were badly in 

 need of repotting, even in early summer, and had they been placed in 

 larger pots the difference in the growth of the plants in the two soils 

 w^ould have been much greater than it was. 



That the influence of the leaf mold was directly deleterious and 

 that the poor growth of the blueberry plants in it was not due to the 

 lack of some element that might have been furnished b}^ the addition 

 of a small amount of the good blueberry soil is show^n by certain inter- 

 mediate experiments. Along with the cultures described above were 

 carried two others in which the soil mixtures contained both peat and 

 leaf mold. In the first, in which the proportion was peat 5, mold 3, 

 sand 1, and loam 1, the average height of the plants on May 29 



193 



