xt7vhh6c462k https://nyx.uky.edu/dips/xt7vhh6c462k/data/mets.xml   Kentucky Agricultural Experiment Station. 1965 journals 153 English Lexington : Agricultural Experiment Station, University of Kentucky Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Progress report (Kentucky Agricultural Experiment Station) n.153 text Progress report (Kentucky Agricultural Experiment Station) n.153 1965 2014 true xt7vhh6c462k section xt7vhh6c462k A THE INFLUENCE OF
PLASTIC MULCHES AND FERTILIZER RATES
p ON THE PERFORMANCE OF
SWEET POTATO VARIETIES IN KENTILQKY
By Dean E, Knavel and H. C. Mohr
Progress Report 153
UNIVERSITY OF KENTUCKY
AGRICULTURAL EXPERIMENT STATION E
Department of Horticulture
Lexington /

 THE INFLUENCE OF PLASTIC MULCHES AND FERTILIZER RATES
ON PERFORMANCE OF
SWEET POTATO VARIETIES IN KENTUCKY
By Dean E. Knavel and H. C. Mohr
The acreage of sweet potatoes in Kentucky decreased from 14,1`78 acres in 1899
to 2. 3 acres in 1960. However, yields per acre nearly doubled, from approximately
65 bushels in 1899 to 113 in 1960. Average yields per acre reported for the years 1943-
52 were equivalent to those reported during the same period for states with greater
acreage than Kentucky's. .
The decrease in the state's acreage over the last 60 years may be attributed to
several factors, of which the lack of facilities for curing the potatoes properly after
harvest is probably the most important. Uncured potatoes had to be sold quickly on
local markets, resulting in an oversupply and a drop in price.
The loss of land best suited for high quality sweet potato production may have U
influenced production decline also, since much of the sandy—loam soil (thought to be ”
best for producing quality) has been lost to urbanization.
However, with rapid, long-distance shipping, low-cost curing facilities, new
production techniques such as the use of plastic mulches, and improved varieties, Ken-
tucky growers should be able to produce efficiently a high quality sweet potato. ’1`he use
ol` plastic mulches has been shown to increase yields in several vegetable crops. There-
fore, trials were initiated to determine the value of plastic mulches for sweet potato
production and to determine the most beneficial fertilizer practices for use with plastic .
mulches.
CULTURAL PROCEDURES _
Seven varieties, Porto Rico, Copperskin Gold Rush, Centennial, Georgia Red,
Bunch Porto Rico, and Nancy Hall, were compared in 1963 by growing with and without ·
black and clear plastic mulches. Daethall, an herbicide, was used at the recommended
rate under the clear mulch to control weeds. The varieties in the unmulched plots
received regular cultivation for weed control.
A 12-12-12 fertilizer was broadcast at the rate of 1000 pounds per acre and 4
clnskccol into the soil prior to planting. The soil was mounded into rows before the
plastic films were laid. and planting was done through slits made in the plastic after ·
it had been placed over the mulch-treatment rows. The plants were spaced 18 inches _
apart in rows spaced ·l feet apart. Each sub-plot contained 10 plants of each V3I‘i€'£y.
and the treatments were replicated 4 times.
lProduct of Diamond Alkali Company.

 3
In 1964. Allggld and Nancy Hall were grown with and without black plastic mulch
at various fertilizer rates. The fertilized plots received nitrogen from ammonium
nitrate. phosphorus from superphosphate. and potassium from potassium sulfate. The
following combinations of fertilizer treatments. in pounds per acre. were used:
up lMWw`i{il D Aigéog K“gOM S if O   Mm A
O nwliwf 04 4 04 T K0} { (checl<)H A l if
2. 50 0 0
3. 0 50 0
4. 0 0 200
5. 50 0 200
6. 0 50 200
7 50 50 0
it MMEQO 150 .200     _.
The plants were set 15 inches apart in rows spaced 3 feet apart. The rows
were prepared and the plastic laid as described for the 1963 experiment. Other cul-
tural practices were similar to those in 1963
The vines were cut immediately after the first frost each year in October. and
the potatoes were dug and graded as either marketable or non marketable. The non--
marketable consisted of non enlarged roots and excessively large. mis—shapened potatoes
The potatoes were cured at 85OF for 3 weeks and stored at 50 600F.
RESULTS OF EXPERIMENTS
1963
The use of black and clear plastic mulches increased yields of the marketable
grade and resulted in fewer non—marketable potatoes (Table 1).
Centennial. Porto Rico. and Nancy Hall were the highest yielding varieties with
the clear plastic mulch The range from low to high yield was less for varieties grown
with clear plastic mulch than those with the black plastic mulch
1964
Results show that black plastic mulch increased total yields of marketable sweet
potatoes (Table 2) The varieties performed best with plastic mulch when either 50 /
pounds per acre of nitrogen or when nitrogen plus 200 pounds per acre of potassium
({420, was applied
Allgold showed the largest increase in yields of potatoes. with and without plastic
mulch and had the highest percentage of marketable roots at all fertilizer levels with
and without plastic mulch No differences in keeping quality of potatoes could be
observed between varieties after 6 months’ storage for either year. All varieties in
the test. when bedded. proved to be adequate producers of plants.

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CONCLUSIONS
The use of plastic mulches was shown to increase yields of sweet potatoes in U
both years of the trials. Porto Rico, Centennial, and Nancy Hall were the highest
yielding varieties, with and without plastic mulches, in 1963. Allgold out-yielded
Nancy Hall in 1964.
The greatest response from additional amounts of fertilizers was with the use
of plastic mulch. Plants fertilized with 50 pounds per acre of nitrogen and 200 pounds
of potassium (K2O) per acre gave the highest yield of roots under conditions at Lexington,
Ky. The sweet potato varieties tested did not show any response to additional amounts
of phosphorus. Also, high potassium without nitrogen reduced yields and, therefore, .
nitrogen appeared to be essential with potassium. _
2M-9-65