THE POTATO 361 



systematic rotation of crops. Potatoes following clover 

 is usually considered an advantageous rotation, because, 

 with this practice, the soil not only has a good supply of 

 humus but an additional supply of nitrogen which can be 

 utilized. An old sod turned under may cause consider- 

 able trouble from white grubs, which sometimes practically 

 destroy a potato crop ; but when a short rotation is prac- 

 ticed, this trouble is not so likely to become serious. Pota- 

 toes, wheat, and clover; or potatoes, strawberries, and 

 clover will make a good three or four year rotation. When 

 planted on sod land, the plowing should be done in the 

 fall and the land well worked down in the spring with a 

 disk and smoothing harrow before planting. 



382. Planting the seed. The time of planting varies 

 in different sections of the country. Generally the seed 

 should be planted by May 20 for best results ; however, 

 in some sections it is June 20 before the late potatoes 

 are planted. 



383. Sun sprouting. It is often difficult to keep pota- 

 toes from sprouting badly and shrinking in early spring 

 before time for planting. This problem can often be 

 solved by rubbing off all white sprouts and placing the 

 potatoes in the sunlight for two or three weeks before 

 planting. They can be spread out on the barn floor, or 

 shelves can be built upon the south side of the barn or other 

 building for containing them, and they may then be 

 spread out in a single layer and left exposed to the light 

 until they are wanted for planting. A short green sprout 

 will develop in place of the long white ones usually seen in 

 the cellar. The potato thus treated can be planted as 

 late as the first of July and yet a good crop may be secured. 

 It is desirable to select the seed stock for the following 

 season from this late planted crop, which, however, would 



