10 CIRCULAR 



It is a popular belief that the lateral root development of a tree 

 corresponds closely to its limb spread, but these excavations indicate 

 that it is probably much greater. Ideas of depth of root penetra- 

 tion are usually vague. Experienced orchardists expressed the opin- 

 ion that midway between trees such as were examined roots would be 

 found only within a few inches of the surface. Nearer the trees 

 they thought they might extend to a depth of possibly 3 feet. Ex- 

 cavations in soils favorable for deep rooting showed at the outer 

 limb spread roots at a depth of 8 feet, and midway between four 

 trees, more than 20 feet from the trunks, roots 5 feet or more deep. 

 These deeper rootlets in many places seem nearly free from feeder 

 rootlets, but in some places small white rootlets which were ap- 

 parently growing were found many feet below the surface when the 

 tree above ground was dormant and the ground frozen. 



In the Gerald soils it was found that where the clay layer is slightly 

 friable and less tough and plastic than in the typical soil, the roots 

 not only penetrate this layer but seem to make a larger growth 

 below the tight clay than in it. On the other hand, where the clay 

 layer is highly developed the roots do not reach far into it. Where 

 there is a well-developed cemented, hardpan a few roots grow for 

 some distance into it but not through it. 



Since the downward development of roots in the Gerald and 

 Lebanon soils is restricted by impervious subsoils, it might be con- 

 cluded that lateral development would be correspondingly greater. 

 In the trees examined, this was not the case. On the contrary, 

 lateral development of roots on soils with tight subsoils seems to be 

 less than on soils with open subsoils. 



One other important observation was made. In soils having deep, 

 well-drained subsoils all roots examined were found to be in a live, 

 healthy condition. Even those which had become flattened and 

 twisted in pushing through gravel had the reddish-brown bark and 

 white inner layers characteristic of healthy roots. On the other hand, 

 in the wet, poorly drained, and poorly aerated subsoils above im- 

 pervious layers, many small dead roots were found. Numerous other 

 roots were in an unhealthy condition, having enlargements from 

 which grew masses of short fine rootlets. 



In excavations made in soils having tight subsoils practically all 

 roots were found within a soil layer extending from the surface 

 to a depth of about 30 inches. In soils having open subsoils this 

 layer, penetrated by the roots, was found to be more than twice as 

 deep. 



At a conservative estimate, each tree 20 or 25 years old planted on 

 soil with open subsoil is able to draw on the moisture and plant-food 

 resources of 5,000 cubic feet of soil. Trees of the same age planted 

 on land with a tight subsoil are able to draw moisture and food from 

 less than half that volume. In the area studied, an abundance of 

 both the Baxter and Newtonia soils is available for orchard planting, 

 but plantings are still being made on the less desirable soils. 



The following tabulations give the weight of dry roots taken from 

 excavations 30 by 48 inches in size, beneath the outer limb spread 

 of trees. Each is fairly representative of all trees on similar soils 

 where excavations were made. 



