Spike-toothed harrows (Fig. 56).  The teeth of these harrows are round, square or diamond-shaped spikes fastened into a wood or iron frame.  The teeth are set in a vertical position or are inclined to the rear.  These harrows are shallow in their action; they run easily but tend to compact the soil more than the other types and are therefore better adapted to loose soils and to finishing off after the work of the deep cutting harrows.  They are also used for covering seeds.

[Illustration:  FIG. 56.—­SPIKE-TOOTHED HARROWS.]

[Illustration:  FIG. 57.—­A COULTER-TOOTHED HARROW.]

[Illustration:  FIG. 58.—­A PLANK HARROW.]

Coulter-toothed harrows. The coulter-toothed harrows (Fig. 57) have teeth resembling the coulter of a plow twisted or bent into various shapes.  The Acme is a good example of this class of harrow.  It cuts, turns and pulverizes the surface soil somewhat after the manner of the plow.  It prepares a fine mulch and leaves an excellent seed bed.  It is an excellent harrow to finish off with after using a rolling cutter.

Chain harrows. The chain harrow consists of a web of chains linked together.  They have a wonderful power for breaking clods and are useful for collecting weeds.  They shake the dirt from the weeds and roll them into heaps.  Chain harrows tend to compact the soil.

Brush harrows. The brush harrow is a primitive form made by fastening brush to a long pole.  Brush harrows are quite useful for brushing in seed and for pulverizing manure broadcasted on grass lands.

Plank harrows. The plank harrow (see Fig. 58) is made of several planks fastened together so that each plank overlaps the next one to it, like the clapboards of a house.  This harrow is as good as a roller in fining and smoothing the surface soil.  It is an excellent tool to use alternately with a spike or coulter-toothed harrow on lumpy soil.  This tool rasps or grinds many of the lumps or clods which slip by the harrow teeth and presses others into the ground so that the harrow following can get a grip on them.  It is a harrow that can be made on any farm.  This planker is an excellent tool to smooth the surface, for broadcasting small seeds and for planting truck crops.

ROLLING

The objects of rolling are: 

To compress the surface soil so that the harrow will do its work more efficiently, also to break clods or lumps that may have resisted the action of the harrow.

To smooth the surface of the soil for an even distribution of small seeds, and to firm the soil around such seeds after they are planted so that they will keep moist and sprout readily.

To give compactness to soils that are light and loose and thus enable them to hold moisture and plant food better.

To press into the ground the roots of plants partly dislodged by the frost.