38 SUCCESSFUL FARMING 



a granular structure is found in what is known as buckshot land. Such 

 a soil when plowed breaks up into small cubical fragments an eighth of 

 an inch to a quarter of an inch in size. The granular structure facilitates 

 the circulation of the air and soil moisture, permits easier penetration by 

 plant roots and lessens the difficulty of cultivation. 



Granular Structure. The granular structure may be improved by 

 tillage. Every time the soil is plowed, cultivated, disked or harrowed, 

 it is pulverized and broken up into particles, each formed of a larger or 

 smaller number of grains. Granular structure is also improved by good 

 drainage. When the body of the soil is saturated or completely filled with 

 water the soil particles move with little resistance and tend to arrange 

 themselves into a compact mass. This fact is taken advantage of in 

 filling excavations, and when the soil is returned to the excavation water 

 is turned into it in order that it may settle compactly, so that when once 

 filled no depression will occur at the surface. Soils that are thoroughly 

 underdrained seldom, if ever, become saturated, so that there is no 

 opportunity for the soil particles to arrange themselves in this ccmpact 

 mass. Consequently, a soil of this character when once drained gradually 

 assumes the granular structure through plowing and cultivation, together 

 with the penetration of the roots of the plants and the work of insects and 

 worms. This is further facilitated by the thorough drying of the soil in 

 periods of prolonged drought. 



The process of alternate freezing and thawing also has an influence 

 on structure. As the water in the soil solidifies it expands and causes 

 an elevation of the soil, making it more porous. As it thaws and the water 

 again becomes liquid the soil does not fully return to its original position, 

 and consequently its tilth is improved. 



Granulation Improved by Organic Matter. Granular structure is 

 also improved by the addition of organic matter to the soil either as barn- 

 yard manure or the residues of crops turned under. The organic matter 

 incorporated with the soil occupies spaces that would otherwise be occupied 

 by soil particles, and upon its gradual decay it leaves small cavities which 

 separate small groups of soil particles. Plant roots are also influential 

 in improving the structure of the soil, first, by an actual moving of the 

 soil particles due to the enlargement of the roots as they grow; and, 

 second, by the gradual decay of these roots, which leaves minute channels 

 in the soil through which air and water find free passage. Earthworms 

 open channels of considerable depth, and also incorporate in the soil the 

 organic matter upon which they live. 



Good Tilth Important. It is common to speak of the soil as having 

 a good or poor tilth. A soil in good tilth means that it is in good physical 

 condition, or that it has a granular structure that makes it the best pos- 

 sible home for the plants to which it is adapted. The degree of granu- 

 lation desired will be determined to considerable extent by the character 

 of crop that is planted. Corn and potatoes, demanding a rather open 



