PRESS BULLETIN No. 302
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
FERTILIZERS FOR SWEET POTATOES
JOHN M. SCOTT
The sweet potato is one of the most important crops grown
in Florida. It is a source of food for a large part of the rural
population of the State. It is also used to a large extent for feed-
ing all classes of livestock. Few people realize that the sweet
potato crop in the last few years has been nearly equal in
value to that of the upland cotton crop, and to half of that of the
corn crop of the State.
In the spring of 1915, a fertilizer test for sweet potatoes was
begun, on land that had been used for a fertilizer test on Jap-
anese cane, during the previous seven years. The potatoes were
planted in the same plots and given the same fertilizer treat-
ment as the Japanese cane. The land on which this experiment
was conducted was a fair grade of high pineland. The sweet
potatoes grown in 1915 followed Japanese cane while the 1916,
1917 and 1918 crops followed cotton. Eight plots were used
in this test.
The same amounts and kinds of fertilizer were applied to
each of the sweet potato plots as had been applied to the Jap-
anese cane and cotton in previous years.
The same number of pounds of fertilizer was not applied to
every plot, but each plot received the same number of pounds
of plant food of each element.
The first three plots received incomplete fertilizers, the next
four plots a complete fertilizer, and the eighth plot a complete
fertilizer together with ground limestone. The fertilizer was
given into equal applications. The first application was made
on May 30, and the second on July 19. Triumph sweet potato
draws were planted May 10, in rows 6 feet apart, and were
set 16 inches apart in the row.
February 1, 1919
The yields were determined by weighing the sweet potatoes
from each plot and figuring them 60 pounds to the bushel. The
yields are given in bushels per acre.
Plot I which received no phosphorus produced 245.6; plot
II which received no ammonia produced 221.6; plot III which
received no potash produced 99.6; plots IV, V, VI, and VII
which received complete fertilizers produced 259.6, 252.0, 216.0,
222.0, respectively; and plot VIII which received a complete fer-
tilizer plus ground limestone produced 269.6 bushels an acre.
Plot I which received no phosphorus produced 153.6; plot
II which received no ammonia produced 177.6; plot III which
received no potash, 86.4; plots IV, V, VI, and VII which received
complete fertilizers produced 228.8, 182.6, 128.0, 203.2 respec-
tively; and plot VIII which received a complete fertilizer plus
ground limestone, 110.4 bushels an acre.
Plot I which received no phosphorus produced 222.4; plot II
which received no ammonia produced 240.0; plot III which re-
ceived no potash produced 72.0; plots IV, V, VI, and VII which
received complete fertilizers produced 294.4, 276.8, 320.0 and
251.2; plot VIII which received a complete fertilizer plus ground
limestone gave a yield of 232 bushels.
Plot I which received no phosphorus produced 113.6; plot. II
which received no ammonia produced 161.6; plot III which re-
ceived no potash produced 60.8; plots IV, V, VI, and VII which
received complete fertilizers produced 161.6, 249.6, 163.2 and
153.6. Plot VIII which received complete fertilizer plus ground
limestone produced 153.6 bushels per acre.
An average of the yield in bushels per acre for the four
years is: plot I 183.8; plot II 200.2; plot III 79.7; plot IV 236.1;
plot V 240.2; plot VI 206.8; plot VII 207.5 and plot VIII 191.4.
This shows that plot III which received no potash produced the
smallest yield, while plot V which was fertilized with 112 pounds
dried blood, 84 pounds muriate of potash and 224 pounds acid
phosphate produced the largest yield per acre.
State papers please copy.