6 CIRCULAR 9 5, U. S. DEPARTMENT OF AGRICULTURE 



Soils of the second class allow much deeper rooting, supply more 

 abundant moisture, and permit of the use of much greater natural 

 food supplies. 



ROOT GROWTH OF FOREST TREES 



Pioneers in this area regarded the native forest trees as indicators 

 of soil conditions. Walnut, red and white oak, large elm, dogwood, 

 and some other trees were recognized as indicators of good soil. 

 Blackjack-oak land was not believed to be so good, and post-oak 

 ridges and prairies were left for open range. Later settlers, in 

 selecting sites for orchards, were less discriminating. The level sur- 

 face of the prairies and of the post-oak ridges seemed to them espe- 

 cially favorable for orchard planting, and such areas were so used 

 to a great extent. 



The root development of the forest trees may be seen in many 

 places in roadside cuts and at the base of upturned stumps, which 

 have been pulled in the building of roads, or of trees uprooted by 

 storms. 



Although the prairies are normally grasslands, in many places 

 around the edge of the prairies low-growing post oak and small 

 black hickory trees have encroached. Where these have been pulled 

 in road building the roots in many places are found to have grown 

 down to the top of the impervious clay layer where they have spread 

 out as a mass of fine rootlets. These grow along the top of the 

 clay but not far into it and form brushlike masses resembling 

 " witches brooms " or rosettes like those frequently seen on the 

 branches of trees in an unhealthy condition. Upturned stumps of 

 trees which have grown on the Lebanon soils show that the roots 

 grow to the top of the hardpan but not far into it. (PL 2, B.) In 

 striking contrast, roots of trees on soils having open subsoils may 

 be found in many places growing to a depth of many feet. Even 

 where the soil is very gravelly but not cemented the roots find their 

 way between and through the gravel. (PI. 3, A.) 



RELATION OF SUBSOIL TO STAND AND SIZE OF TREES 



In order to determine the relation between subsoil and the stand 

 and size of trees, counts to determine the percentage stand and 

 measurement of trunks were made in a large number of orchards 

 distributed through the area. 



To determine the percentage stand orchards were selected in which 

 the original plantings range in age between 15 and 25 years. In 

 these, blocks of from 2 to 5 acres, as nearly as possible representative 

 of the orchard as a whole, were selected and the trees of the original 

 planting in fair or good bearing condition were counted. This num- 

 ber divided by the number originally planted was taken to 

 represent the percentage stand of the orchard. 



Where soil surveys had been made the soil type shown on the map 

 was accepted in determining to which class the soils of the orchard 

 belong. Where no such survey had been made the soil was examined 

 to determine whether it had an open or tight subsoil. 



Orchards were divided into two classes — commercial orchards in 

 which the acreage ranges between 5 and 160 acres and domestic 



