12 THE HANDBOOK FOR PRACTICAL FARMERS 



which will help to prevent the soil from running together during 

 the spring thaws. 



6. Penetration of roots, and the burrowing of earthworms, 

 ants and other animals are important agencies in soil improve- 

 ment. The roots of plants make their way through the soil in 

 every direction, the crops having fine fibrous roots like the buck- 

 wheat, being especially noted for their beneficial effect on heavy 

 soil. It is generally conceded that the best way to bring a poor 

 clay soil into condition is to put it down to grass for a few years, 

 after which it turns up loose and friable. The mat of vegetation 

 formed by plants, especially grasses, protects the soil from beat- 

 ing rains, the puddling action of melting snow, and from washing 

 or erosion. Plants grown for the purpose of protecting the 

 surface of the soil are known as cover crops. 



In order to accomplish good plowing the furrow slice must 

 be turned to the proper angle and should be straight and uni- 

 form. To set the furrow slice at the proper angle it is necessary 

 that the depth of the plowing should be about one-half the width 

 of the furrow. If the plowing is too shallow the furrow slice 

 is inverted. Wlien the furrow slice is completely inverted, 

 stubble and sod or rubbish are thrown to the bottom of the 

 furrow where they tend to prevent the proper contact of the 

 furrow slice with the subsoil. If, on the other hand, the furrow 

 slice is set well on edge, there is a good chance for the capillary 

 rise of moisture, rainfall is more readily absorbed, and the sod 

 and rubbish are more evenly distributed throughout the depth of 

 the f urroAV. ^Yhen the soil 1)ears a heavy sod so that the furrow 

 holds its form, packing by heavy rolling is desirable, so as to 

 bring the sod in closer contact with the subsoil and to eliminate 

 intersoil spaces that are too large. The diagrams of Fig. 3 

 show the proper position of the furrow slice after it has been 

 turned by the plow. 



The average depth of plowing in the United States is probably 

 not over five inches. For most soils, especially those having a 

 compact subsoil, deeper plowing is highly beneficial since by this 

 means their moisture capacity may be greatly increased and 

 deeper root penetration secured. On light, sandy soils deep 

 plomng should be accompanied by generous applications of 

 manure or other organic matter. 



Several attachments are used on the plow for special condi- 

 tions of the soil. On sod land the jointer much improves the 

 result. This is a miniature plow which cuts the surface roots 

 and turns under the edge of the furrow, giving a smoother 



