72 PRODUCTIVE FARMING 



time (Fig. 43). The two-plow gang is usually drawn by 

 horse power, but larger gangs are frequently drawn by steam 

 or gasohne traction engines. 



Forms of Mouldboards. — Plows have three main forms 

 of mouldboards, suited to the different purposes of the farm. 



The mouldboard for turning over sod is long from the 

 front point to the rear, is very oblique, and has a very slight 

 curve. The rear of the mouldboard turns the slice more 

 nearly upside down than the other forms. . 



The mouldboard for stubble ground is extremely different 

 from that of the sod plow, being very short, steep, and much 

 curved. It bends the furrow shce abruptly and causes it 

 to crumble, leaving it somewhat on edge. 



Fig. 43. — Modern gang plow, turning two furrows at a time. 



The general purpose mouldboard is medium in form 

 between the other two extremes, and is useful where much 

 litter and manure are to be plowed under. 



Fall Plowing. — ^When a field is plowed in the fall it gives 

 more time for the rotting of barnyard manure and other 

 forms of vegetable matter turned under by the plow. The 

 farmer usually has more time in the fall, and the plows may 

 be kept going until the soil is frozen. Heavy soils plowed in 

 the fall are greatly improved and made mellow by alternate 

 freezing and thawing during winter. Many forms of inju- 

 rious insects are destroyed in the upturned soil during the 

 winter. The moisture conditions are bettel* and the crops 



