SUBSOIL A FACTOR IN GROWTH OF APPLE TREES 3 



are embedded. These chert fragments constitute the gravel that is 

 present in the soils over the area. Some of this gravel is red or red- 

 dish brown, rather porous, and not extremely hard, and some is 

 nearly white and very hard and breaks into sharp, flinty fragments. 

 The thickness of this mantle of soil material varies widely, ranging 

 from a few inches to several feet in extreme cases. This red clay 



Figure 1. — Sketch map showing area studied in southwestern Missouri and north- 

 western Arkansas, indicated by dotted lines 



material is not everywhere exposed at the surface, but it lies only a 

 few feet beneath it and is seen in wells and other excavations. 



Further weathering of the red soil material under varying condi- 

 tions has resulted in the formation of soils which vary rather widely 

 in their main characteristics. In general, soils of a region developed 

 from similar parent material and under practically uniform general 

 climatic conditions, as were the soils of this area, vary according to 

 the character of the land surface and of the natural vegetation. 



