PREPARATION OF SOILS FOR POTATOES 133 



Fertilizers for Potatoes. — In the most intensive potato growing 

 districts, commercial fertilizers are used in growing the crop. A mix- 

 ture containing four per cent of nitrogen, six per cent of phosphate 

 and eight per cent of potash will suit the average Irish potato soils. 



Much can be saved by "growing" nitrogen instead of buying it. 

 If an annual crop of green manure is plowed under each year, 

 the nitrogen supply will be abundant. This is particularly true if 

 the green manure is composed of clover, vetch, or some other 

 legume. Barn yard manure will help also to take the place of the 

 nitrogen. Heavy soils are likely not to need as much phosphoric 

 acid. It is also true that application of potash is more important 

 on sandy soils than on heavy soils. Where early potatoes are 

 grown for market, commercial fertilizer will aid materially in 

 producing the crop quickly. The amount saved in getting the 

 crop in to market at a high price will probably pay for the fertilizer 

 used. Growers often use as much as five hundred to one thousand 

 pounds per acre, or more. 



The use of lime on potatoes is apt to cause scab disease but if it is 

 applied on the crop preceding the potatoes in the rotation, the 

 residue in the soil will help the potato crop. If this plan is followed, 

 the best form of lime is ground limestone. 



Preparation of Soils for Potatoes. — Plowing should be very deep. 

 The crop should have a loose open soil. For this reason it is not 

 necessary to have the plowing done long before planting time. It 

 does not need to be repacked as it would be for corn, wheat and 

 other small grain. The so-called deep tillage machines where one 

 disk follows behind the other in the same furrow are best for the 

 preparation of heavy soils for potato growing. Judgment should 

 be exercised so that too much of the subsoil will not be turned to the 

 surface at any one time. If, however, it is done with the disk plow, 

 the subsoil brought up will be so very thoroughly incorporated 

 with the other soil that little or no damage will be done in deepen- 

 ing the soil considerably at one season. 



If a plow is run rather shallow, a subsoil plow which stirs the 

 the bottom of the furrow but does not bring the loose soil to the 

 top will deepen the root bed for the potato crop. If the ground is 

 plowed in the fall as in the northern states, deep disking before 

 planting is very desirable. This is also true if the sod has been 

 turned under in the spring. The disk harrow will cut the sod to 

 pieces and mix the organic matter with the soil. The smoothing 

 harrow used after the disk harrow will prepare the ground well for 



