146 MISSOURI AGRICULTURAL REPORT. 



of soil management to transform into available condition with sufficient 

 rapidity to meet the need of heavy yields. 



3. The necessity for an ample crumb-structure of the soil through- 

 out the effective root z®ne which bad management breaks down and 

 which good management builds up and renders more stable. 



The urgency of an abundance of room deep in the soil is very 

 great. In the first place, we do not sufficiently appreciate that the soil 

 of a field is in reality a pasture upon the internal surface of which 

 available plant food materials grow, through the mutual interaction of 

 a multitude of soil organisms, organic matter, moisture, air and the 

 roots of crops, living and decaying, all of them operating together to 

 bring into solution the more insoluble forms of potash, lime, magnesia 

 and phosphoric acid, so that when the roots of crops spread themselves 

 out over the extensive internal surface, carrying a rich growth of soluble 

 plant food materials, they find themselves in an ample pasture of nutri- 

 tious feed, and growth is rapi^i. But tlie first great requisite of this pas- 

 ture is room ; broad surfaces upon which large amounts of water may be 

 stored to become charged with dissolved plant food materials ; over which 

 organic matter may widely spread to constitute the feeding ground 

 of those miscroscopic forms of life which turn its nitrogen and other 

 plant food elements into forms available to crops ; and these internal 

 surfaces far enough apart to give strong and deep ventilation and ample 

 space into which the roots may spread and find abundant opportunity 

 to set the soil grains aside to make room for due enlargement. 



Upon this chart there has been represented, by drawing to proper 

 scale, the volume of the component portions of the surfase foot of a soil 

 possessing about the medium amount of room which is found in a soil 

 of average productive capacity. The bottom cube in the diagram 

 stands for a cubic foot of undisturbed surface soil, in its normal field 

 condition when well settled toward the end of the growing season 

 after having been plowed 6 to 7 inches deep in the spring of the same 

 season. The second cube represents the volume the dry soil would 

 occupy with the moisture and the air removed and with the soil so con- 

 solidated that all open spaces are obliterated. In this condition its 

 volume would be 764.5 cubic inches or 44.24 per cent of the whole 

 cubic foot. The dry weight of this soil is 73.176 pounds, while the 

 dimension gives a cube a little more than 9 inches on each edge. 

 The third cube on the chart represents the volume of the space in the foot 

 of surface soil which is occupied by air when the amount of moisture 

 present is very near the best amount for good crop conditions. In it 

 there are 581. i cubic inches of space occupied by air, comprising 33.63 

 per cent. That is, the surface foot of soil in good moisture condition 



