Tillage to Modify Soil Texture. 239 



have tended to cut the pins into as many pieces as there 

 were leaves, just as seen in Fig. 76. 



Now the plow has exactly this kind of effect upon the 

 furrow slice; it tends to make it divide into thin layers 

 which slide over one another just as the leaves of the book 

 did, and it is because of this sort of action that a plow pul- 

 verizes a soil as no other tool can. 



295. How Plowing May Puddle Soils. When a soil is too 

 wet its granules are so easily broken .that the plow is liable 

 to shear all the coarser ones into two, three, or more slices 

 just as the pin has been sliced in Fig. 76, thus destroying 

 its tilth by puddling it. 



296. How Plowing May Correct Texture and Improve 

 Tilth. If a soil has gotten out of tilth, has become cloddy 

 or has been partly puddled there is a shape of mold board, 

 a stage of soil moisture, and a depth of furrow slice which 

 will help to restore the tilth best and quickest. When such 

 a soil is the least amount too dry to puddle the plow will 

 shear it into the thinnest slices ; if still drier the layers will 

 be thicker and will form coarser granules. 



When much too dry no shearing can take place at all, and 

 the furrow slice is simply broken into coarse lumps. 



If you bend but a few leaves of the book at a time there 

 is but little slipping, but the thicker the pile of leaves the 

 greater is the sliding and the greater is the tendency to 

 shear. So it is in plowing, the deep furrow pulverizes bet- 

 ter and puddles worse than the thin slice or shallow furrow. 



Again if you bend the leaves gently there is little shear- 

 ing, but if abruptly the sliding is great So if you plow 

 with the low mold board of Fig. 77 you disturb the tilth 

 least, puddled the soil least, and leave the texture coarsest ; 

 but if the steep mold board of Fig. 78 is used there is the 

 greatest danger of puddling if the soil is too wet and the 

 greatest opportunity to pulverize the soil and improve the 

 tilth if the moisture is right. 



297. Forms of Plows. Plows are made with two funda- 



