156 FARM MECHANICS 



ground packs into lumps that an ordinary harrow will 

 not break to pieces. Such lumps roll out between the 

 harrow teeth and remain on top of the ground to inter- 

 fere with cultivation. The clod crusher then rides 

 over the lumps and grinds them into powder. Unfor- 

 tunately, clod crushers often are depended on to rem- 

 edy faulty work on ordinary land that should receive 

 better treatment. Many times the clod crusher is a 

 poor remedy for poor tillage on naturally good land 

 that lacks humus. 



Figure 140. Land Float. Clod crushers and land floats belong 

 to the same tribe. Theoretically they are all outlaws, but some 

 practical farmers harbor one or more of them. Wet land, contain- 

 ing considerable clay, sometimes forms into lumps which should be 

 crushed. 



As ordinarily made, the land float or clod crusher 

 consists of from five to eight planks, two inches thick 

 and ten or twelve inches wide, spiked together in saw- 

 tooth position, the edges of the planks being lapped 

 over each other like clapboards in house siding. The 

 planks are held in place with spikes driven through 

 into the crosspieces. 



FARM ROLLER 



Farm rollers are used to firm the soil. Sometimes 

 a seed-bed is worked up so thoroughly that the ground 

 is made too loose so the soil is too open and porous. 

 Seeds to germinate require that the soil grains shall fit 

 up closely against them. Good soil is impregnated 

 with soil moisture, or film moisture as it is often called, 

 because the moisture forms in a film around each little 



