SUBSOIL A EACTOR IjS t GROWTH OF APPLE TREES 11 



Weight of dry roots in Newtonia silt loam iy 2 miles north of 

 Lowell, Ark. Tree 20 years old and 11% inches in diameter. 



Inches Ounces 



to 8 19 



8 to 15 16% 



15 to 30 7% 



30 to 41 3 



44 to 60 % 



60 to 84 % 



84 to 96 14 



96 to 103— i/ s 



Weight of dry roots in Baxter gravelly loam, near McDowell, 

 Barry County, Mo. Tree 25 years old, 12 inches in diameter. 



Inches Ounces 



to 8 6 



8 to 16 2% 



16 to 30 2 



30 to 45 1% 



45 to 50 % 



50 to 70 % 



70 to 75 14 



Weight of dry roots in Lebanon silt loam, 6 miles west of Benton- 

 ville, Ark. Tree 23 years old, 8y 2 inches in diameter. 



Inches Ounces 



to 10 12 



10 to 17 6 



17 to 30 5% 



30 to 36 % 



Weight of dry roots in Gerald silt loam near Phelps, Lawrence 

 County, Mo. Tree 23 years old, 9 inches in diameter. 



Inches Ounces 



to 10 9 



10 to 18 5% 



18 to 24 14 



24 to 30 % 



Wide variation in the weight of roots in the upper soil layers may 

 be due to the presence or absence of large roots which happen to oc- 

 cupy the area excavated or may be due to heavy applications of manure 

 which have stimulated heavy root growth near the surface. The depth 

 of penetration into the deeper subsoil, even by very small rootlets which 

 weigh but little when dry, is considered of much more importance. 



From the foregoing tabulations it will be noted that in the New- 

 tonia soils roots were found to a depth of more than 8 feet and in 

 the Baxter soils to a depth of more than 6 feet, but that in the Leba- 

 non soils they were found to a depth of only 3 feet and in the Gerald 

 soils to a depth of only 30 inches. 



It will also be noted that in the Newtonia and Baxter soils there 

 is a fairly constant decrease in root growth downward, but that in 

 the Lebanon and Gerald soils there is a tendency for development 

 of heavy root growth immediately above the claypan or the hardpan, 

 with a slight growth but a short distance below the impervious layer! 



The roots from two 20-year-old trees, (a and d), which, grew on 

 Newtonia soils in comparison with two trees, (b and c), which grew 

 on Lebanon soils are shown in Plate 5, A. («, 5, and <?, Ben Davis. 

 and d, Wealthy.) The roots were taken beneath the outer limb 

 spread, from an excavation measuring 30 by 48 inches, were washed, 

 dried, and arranged in the position in which they were taken from 

 the ground, the depth being indicated in feet on the margin of the 



