892 IOWA DEPARTMENT OF AGRICULTURE. 



The success of the potato is largely dependent on the crops preceding 

 it in rotation. If clover or other leguminous plants are grown just pre- 

 ceding potatoes the straw or stubble furnishes organic matter and to 

 the store of .... available nitrogen in the soil. Corn after sod fre- 

 quently precedes potatoes. I find this generally a good rotation. Two 

 years, or three at most, is as long as a field should be devoted to con- 

 tinuous potato culture, though this crop is frequently grown longer on 

 the same land, which naturally taxes heavily the fertility of the soil, 

 and necessitates liberal manuring, as well as involving considerable risk 

 of injury from funges diseases, and especially from the potato scab. 



A clean crop of potatoes can not, as a rule, be grown in land which 

 the preceding year produced scaby tubers. The germs of the diseases 

 once in the soil must be starved out by growing on the infected field 

 other crops, such as grass or grain, for several years. Three or four 

 years rotation gives very satisfactory results. Land seeded to clover in 

 spring and the second year clover plowed under in the fall and third 

 year potatoes, has proved successful. 



To give detailed directions for the preparation of one kind of soil 

 would not apply to others. 



Hence it can only be said that preparation should be deep and thor- 

 ough. Plowing can scarcey be too deep, provided that much of the sub- 

 soil is not brought to the surface. When practicable, the depth should 

 be gradually increased from year to year. Though the tubers are usually 

 cultivated from three to five inches of the surface, the roots feed much 

 deeper, penetrating the soil from twelve to twenty-four inches, or more. 

 Expreience teaches as to extent of the distribution of potato roots in the 

 soil and we desire to emphasize the importance of deep and thorough 

 preparation of the soil for this crop. 



MANUEIA^G. 



The potato requires a liberal manuring, barn yard manure usually 

 alYording a large increase in the crop, for not only does it supply nitro- 

 gen, phosphoric acid and potash, but it improves the conditions of the 

 soil. However its direct application to the potato affords conditions 

 favorable to potato diseases, and an injury to their quality. 



For this reason it is best to apply barn yard manure to corn or grass 

 the year before potatoes are grown. If it is considered necessary to 

 apply it airectly to the potato ground, it should first be well rotted. 



/ 

 VARIETIES. 



The farmer should be his own judge as to varieties, aiming to plant 

 only those that do the best on the kind of soil in which they are to be- 

 planted. Some varieties do well on one kind of soil and are almost 

 worthless on other kinds. 



TIME FOR PLANTING. 



Each community is the best judge of the time for planting. The 

 aim should be to plow the soil as soon as it will crumble nicely, but 

 you should by no means ploy it when it is wet, for if you do you may 



