164 PRODUCTIVE FARMING 



of water taken from the soil during the growing season. The 

 grower therefore finds it necessary to conserve the soil moisture 

 by thorough tillage at the proper times, and by the mainten- 

 ance of dust mulch or straw mulch. The soil should be deep, 

 black, and full of vegetable matter to aid in holding moisture. 



Green Manure. A green manure to plow under in the 

 early spring may be started in the field of corn or other crop 

 the preceding summer. Sow the seed in July or early August, 

 using a mixture of rye, winter vetch and crimson clover. 

 These plants will serve as a winter cover crop and when 

 plowed under will quickly decay and form humus. 



Fertilizers for Potatoes. In States east of the Missis- 

 sippi Valley it is usually found advisable to fertilize the 

 soil for potatoes when grown for market. Barnyard manure is 

 usually applied to the field a year before the potatoes are to be 

 grown there. Green manure or grass sod may be turned under 

 the spring that the potatoes are to be planted; but it should 

 be worked well by disking after the plowing. Fresh manure 

 from horse stables applied the same year that the crop is 

 planted tends to cause the scab disease to develop badly. 



Commercial fertilizers for potatoes are usually applied at 

 planting time and are drilled in the rows after part of the 

 soil has been drawn over the seed potatoes. The fertilizer 

 should not actually touch them. A fertilizer that is rich in 

 potash is desirable for potatoes. A complete mixture may 

 contain these percentages : 2 to 3 of nitrogen, 4 to 6 of phos- 

 phate, 8 to 10 of potash. See Appendix Table VII for in- 

 gredients to use for these mixtures. 



Plowing should be done in the spring not long before the 

 potatoes are to be planted. It must be deep and thorough 

 as the potatoes require a loose bed for growth. The newly 

 plowed ground must not be packed with a roller, but should 

 be smoothed with a common harrow. 



Cutting Seed. The seed pieces are cut in many different 

 ways, with one or two eyes to a piece being the most common. 



