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sizes have to be arranged to fill a given space, and there is almost 

 no limit to the number of combinations that could be made if we 

 did not assort and pack according to standard grades. 



Now soil particles vary as much in size, relatively, as do ap- 

 ples, and hence the soil mixture is exceedingly uneven. All sorts 

 of combination packs have been made and in some of them the 

 particles fit together so snugly that they do not readily crowd apart 

 when a little rootlet tries to find its way down among them. And 

 remember that in plant and tree growth a tiny rootlet always has 

 to blaze the path downward into the soil, the big strong root being 

 a later development. Stiffness, or its opposite mellowness, depends 

 upon the arraiigoucut of the soil grains and not upon their si^e; 

 upon the structure, not upon the texture of the soil. 



Contrary to common opinion the most clayey soils are not the 

 stift'est soils. Bricks are not made of clay alone, but of a rather 

 definite mixture of clay and particular grades of sand. Sometimes 

 we find subsoils that approach in varying degree a bricklike com- 

 position. If brought to the surface by the plow, exposed to the 

 air and left undisturbed for a short time the clods bake, and then 

 are reduced with much difficulty. This could be prevented at the 

 surface if the harrow had followed the plow closely, and if stable 

 manure or other organic matter had been mixed with the soil, but 

 a deep subsoil of this sort is not so easily improved nor is it in- 

 viting to a well-branched fibrous root system. The root systems 

 of some varieties of apples, furthermore, overcome a stiff structured 

 subsoil much more successfully than others. In one of the large 

 orchards of the southern Ozark country Ben Davis trees failed in 

 certain spots. They were very unthrifty and not infrequently 

 died. Yet elsewhere in the same row, with identical slope, exposure 

 and treatment the trees were in excellent condition, and bore heav- 

 ily. The owner believed, too, that there could have been no varia- 

 tion in the stock. An examination of the subsoil showed it to be 

 exceedingly stiff wherever the trees were effected. Following this 

 cue throughout the orchard it was found that another variety 

 (Mammoth Black Twig) was not effected at all by the stiff sub- 

 soil as the roots forced their way down through it, and the trees 

 showed excellent growth. Not satisfied that the chemical condi- 

 tion of the soil in this case might not have some influence upon 

 the unthrifty trees I had made chemical analyses of these soils, 

 but the results showed that there were no chemical differences worth 

 noting. In this particular case it was anoarent that the Ben Davis 

 would not thrive on so stiff a subsoil, whereas the Mammoth 

 Black Twig could successfully overcome it. 



I do not need to call vour attention to the self-evident fact 

 that the condition of this subsoil was not amenable to practicable 

 improvement by the addition of humus, notwithstanding the fact 

 that by this means surface soils may to some extent be changed. 

 In a less pronounced case the growth of deep-rooted crops such as 

 the legumes would have sreatlv improved the phvsical condition 

 of the upper subsoil, but once the orchard is planted, or at least 

 after it has reached bearine aee, the practical orchardist will hardlv 

 try to leave cover crops under his trees so many months of the 



