Tilth and Tillage of the Soil 1765 



tally; the result of this process, when properly done, is a complete pul- 

 verization of the soil. Of course the soil must be in the right moisture 

 condition for the best result, as has already been noted (page 1761). 



Types of moldboard. — The efficiency of the plow depends much on its 

 type and on the manner in which it is used. (Fig. 94.) As a wedge it 

 may have different slopes, or curvatures. For sod land a long, sloping 

 moldboard with a good overhanging is desirable, so that the furrow will 

 be gradually lifted and turned to its new position in one continuous thread. 

 Breaks and ragged edges of the furrow permit it to be torn up by subse- 

 quent preparation. On the other hand, for fallow land (bare soil) a mold- 

 board with much greater curvature is used. This accomplishes more 

 thorough pulverization than would the sod plow. Its draft is correspond- 

 ingly greater. Special types of plow are designed for work on particular 

 kinds of soil. On both sod and fallow land, a moldboard of intermediate 

 curvature is employed. The hillside plow has a peculiar shape of mold- 

 board, hinged so that it can be turned to permit continuous plowing on 

 one side of the land, thus avoiding so much uphill pulling by working 

 across the slope. There is also a considerable variety in the construction 

 of these implements, and different materials are used in the soil-friction 

 parts. For example, on gumbo clay a moldboard of special composition 

 is required. Various modes of construction are designed for supposed 

 mechanical superiority and convenience. 



Right position of furrow. — In order to accomplish good plowing, the 

 furrow should be turned to the proper angle and should be reasonably 

 straight. This requires a particular proportion or relation between the 

 depth and the width of the furrow. (Fig. 95.) The best angle with the 

 surface of the subsoil at which to lay the furrow is thirty to forty-five 

 degrees. In order to obtain this angle it is necessary that the depth of 

 plowing be about one half the width of the furrow. When the plowing 

 is too shallow (one third or less of the width) the furrow slice is inverted. 

 Stubble and rubbish are thereby thrown in the bottom of the furrow, 

 where they tend to break contact with the subsoil and are poorly mixed 

 with the soil. On the other hand, when the furrow slice is set well en 

 edge there is fair chance for capillary rise of water, rainfall readily sinks 

 into the soil along the face of the furrow, and sod and rubbish are more 

 thoroughly distributed from the top to the bottom of the cultivated soil. 

 There is also better ventilation where decay should be most active. At 

 the same time the upper angle of the inverted furrow slice may be easily 

 pulverized and worked into a good seed bed. When the soil bears a 

 heavy scd so that the furrow slice holds its form, heavy rolling and packing 

 are desirable so as to bring it in closer contact with the subsoil and to 

 avcid intersoil spaces that are too large. 

 121 



