136 The Potato 



disk and its variation, the cutaway, are used most in 

 soils nearly or quite free from stone. With these the 

 soil can be thoroughly fined nearly to the depth of the 

 plowed furrow. The disk will cut up sods or straw and 

 will work in soils so full of weed-roots that other types 

 of harrow^s will be clogged. The spring-tooth harrow is 

 used more than the disk in sections wdth stony soils. It 

 pays to keep the cutting edges of the disk or the points 

 of the teeth sharp. The spike-tooth smoothing harrow 

 should follow the disk to level the surface before plant- 

 ing. It is also valuable to keep a surface mulch before 

 planting and to kill w^eed seeds that have sprouted. 



The roller is a tool of great value, but is often used 

 with poor judgment in potato-growing, because it has 

 considerable weight for the small surface. Its action, 

 resting on the soil, is to firm the earth to a considerable 

 depth, something seldom necessary with potatoes unless 

 on very light soil, and is often harmful. Used to follow 

 the plow after plowing in the spring, it may help to pre- 

 vent sods on edge from making open spaces in the soil. 

 Too often it is used with the idea that it is necessary, 

 as with the grains and grass seeds, to firm soil around 

 the seeds to furnish moisture for germination. The 

 roller is used to assist the germination of grain and grass 

 by packing the soil around them, causing it to become 

 damp by the capillary rise of water. Such seeds are 

 dry and need water to start, and their small size demands 

 closely packed soil for the benefit of the roots. Unlike 

 the dry grain seeds, the large potato seed-pieces have all 

 the water they need, 80 per cent, and can grow for weeks 

 without any from the soil. This fact is familiar to those 

 who have seen potatoes in cellars send shoots to the 

 length of several feet. Soils are seldom too loose for the 



