178 IRISH POTATO ENTERPRISE
Pern
108 pounds of high-grade acid phosphate and about 110 pounds
muriate of potash. These data may serve as a general guide if we
remember that smaller yields remove less plant food, but the same
relative amounts. If we supply most of this nitrogen by plowing
under barnyard manure or legume crops, we may avoid much of
the expense of purchasing nitrogen.
The chief chemical needs of any soil in which the plant food
is not well balanced for the growth of potatoes is indicated by the
character of growth. These characters have been indicated in the
soils chapter. A heavy legume growth used as green manure should
supply to each acre seventy-five to eighty pounds of nitrogen. It
would also return nineteen or twenty pounds of phosphoric acid
and about fifty pounds of pot-
ash. The use of green manure
is, therefore, to be highly
recommended.
Applying Commercial
Fertilizers.—When commer-
cial fertilizers are used the
planters are equipped with fer-
tilizer attachments by which
the fertilizer is applied at
planting time. A complete
fertilizer of the formula 4-6-8 Fic. 110.—Applying fertilizer with a 3-row dis-
or 2-6-10 may be mixed at tributor for potatoes. (Stuart’s The Potato.)
home for potato growing. Apply four to six hundred pounds of
this mixture per acre. (Fig. 110.)
Preparation for Planting.—Choose fields for potatoes on which
a green crop or sod has been grown to turn under. If an early
spring crop is to be planted plow the land the preceding fall. In
the spring as early as conditions will permit disk the soil well
and harrow the surface to produce a mellow seed bed. If late or
main crop potatoes are to be grown an early planting is not so
essential. Spring plowing is often practised. If a green cover crop
has been growing the preceding fall and winter, it would be better
to plow that under in the spring early enough to allow it to become
well incorporated with the soil before planting time. The seed bed
for planting potatoes should be deep and mellow and not so com-
pact as for small grains. In preparing a seed bed a level surface
is left in nine-tenths of the potato fields of the country. But in
a few sections where natural drainage is poor or when water might
stand if the season should prove to be wet, slight ridging or bed-
