SUBSOIL A FACTOR IN GROWTH OF APPLE TREES 9 



expressed by orchardists is that the fruit is more highly colored and 

 probably better flavored on good soils than on the poorer soils, 

 especially the Gerald soils. 



Ben Davis and Gano varieties were extensively planted in this area 

 from 20 to 25 years ago, and most of the trees examined were of 

 these varieties. However, a number of orchards of York Imperial, 

 Jonathan, Winesap, and others were included, and the same relation 

 was found between subsoil and the growth of trees. 



SUBSOIL AND ROOT DEVELOPMENT OF APPLE TREES 



In order to determine the effect of subsoil conditions on the root 

 development of apple trees a further study was made. For this 

 purpose there were selected apple orchards, situated on representa- 

 tive soils, in which the trees were between 20 and 25 years of age and 

 had made a good normal growth. In each of these orchards a 

 straight-walled excavation 30 by 48 inches was made. The soil was 

 removed by layers, and from each layer the apple roots were care- 

 fully picked out, placed in paper bags, and numbered. Later they 

 were washed, dried, and weighed. A few excavations were made near 

 the trunks of trees and a few midway between four trees. The 

 greater number, however, were made beneath the outer limb spread, 

 in most places between 10 and 15 feet from the trunk, and these were 

 made the standard for comparison. Forty such excavations, ranging 

 in depth from 18 inches to 12 feet, were made. 



The trees examined had trunks between 8 and 13 inches in diameter 

 at the base. They had no central or tap roots but sent out from 

 three to five large roots laterally a few inches below the surface. 

 The largest roots exposed in the excavations were only from 2 to 4 

 inches in diameter near the trees, and 3 or 4 feet from the trunk 

 they tapered to half that size. Eoots 1 inch in diameter at the 

 outer limb spread were rare. With the exception of these few larger 

 roots and their main branches, the rootlets range in diameter from 

 that of a lead pencil to that of a very fine thread. Small roots, 

 however, are numerous, and when dry they weigh but little. This 

 accounts for the very small weight of roots in the deeper layers. 



These excavations afforded an excellent opportunity for study of 

 methods of root growth and penetration. Apple-tree roots respond 

 in a remarkable way to environment. They seem as sensitive to 

 soil conditions as plants above ground are to heat and light. When 

 the surface soil is broken apart masses of tender, light-colored root- 

 lets are shown. These spread from ganglionlike centers and are so 

 delicate that they are completely dried out by a few minutes' 

 exposure to sun and air. Loose soil along old root channels, mellow 

 soil where animals have burrowed, or surface soil covering draintile 

 seems to be sought out and followed. Wormholes and cavities made 

 by ants and other insects form tunnels which in places are almost 

 completely filled with rootlets. The bark of oak roots from which 

 the wood has decayed forms hollow cables inclosing small rootlets 

 for long distances. Where porous chert is reached small roots wedge 

 themselves between the masses, penetrate cavities, and spread a net- 

 work of fine rootlets over the smooth surface, pushing their way 

 between rocks and the surrounding clay. 



