AGRI CULTURAL RESEARCH CENTER, IFAS, UNIVERSITY OF FLORIDA
m \ Dover, Florida
Dover ARC Research reportt SV1974-2 October, 1974
FERT LIZATION, TRANSPLANT CHILLING AND PLANTING DATE OF
THE "TIOGA" STRAWBERRY IN PLANT CITY AREA
E. E. Albregts and C. M. Howard
Many items are considered by growers in managing their strawberries. Among
these are fertilizat' n, irrigation, planting date, and transplant chilling.
Fertilization and irr gation imply a host of other problems, such as, fertilizer
carrier, rates, and p acement, bed height, and irrigation volumes which in turn
affect fertilizer mov ment and availability. Planting date and chilling of trans-
plants before setting in the fruiting field affect earliness of fruiting, plant vigor
and growth, and quite often the total seasonal yield. Trials conducted at ARC,
Dover have attempted t solve some of thes.egroblems for the variety 'Tioga'.
Source, placement, and leaching. Strawberry plants are shallow rooted with most
of the root mass locate in the top 12 inche~E'fgthe~q jp nt bed. Thus, the most
efficient use of the fe tilizer is obtained when it rrefains in the upper portion of
the bed. Generally all the fertilizer is placed in the bed before application of
polyethylene mulch. On purpose of th.A gb ich .o retard leaching. However, to
start the young plant 1 rge volumes ofwaterx-A1.ep 1dd by overhead irrigation
iftar transplanting. Th plant bed may become --'satur ae'dwith water, and then
fertilizer movement occu s. Water and fertilizer move inward as well as upward and
downward during and afte bed saturation. Therefore, the placement and solubility
of the fertilizer along th the moisture content in the plant bed are very
important. The young tr splant with its small root mass needs a ready source of
plant nutrients to begin ts rapid early growth. But if considerable movement of
the fertilizer has occurr d during the 'plant starting' period then none may be
available. In addition, f a soluble fertilizer is applied between the plant and
the side of the bed, it my cause a plant burn if placement is not accurate or as a
result of salt movement t yards plant roots when beds were saturated. If the
fertilizer applied between plant and side of bed is derived from a resin coated or
slowly soluble inorganic s urce then leaching would be reduced, burn should not
occur, and some nutrients should be available to the young plant. Use of an organic
fertilizer (sludge) for th s purpose probably would not suffice since nitrifying
bacteria are needed to dec pose the sludge before it is available to the plant.
Most of the bacteria are ki led during fumigation. These bacteria will increase in
number with time and decomp se the sludge later in the season.
The use of irrigation or cold protection will also result in fertilizer
leaching similar to that occurring at transplanting. The situation is more serious
at this time since the organ c fertilizer (sludge) may be mostly decomposed,
depending on climatic condi ons, and a large part of the fertilizer could be
leached from the root zone. Most growers use organic fertilizer (sludge) for straw-
berries despite University t ial results. Trials at Gainesville and Dover have
shown no response of organic ver inorganic fertilizer. However, cultural practices
employed in Gainesville did n t include the use of large amounts of water to start
plants after transplanting or to irrigate for cold protection. At Dover, beds were
not leached after transplant g since low irrigation rates were used to start the
plants. High rates of fertil zer were applied and this probably tended to offset
any serious fertility losses rough leaching from cold protection irrigation. The
grower undoubtedly losses a la ge portion of his inorganic fertilizer at time of
transplanting but with about 5 % of his nitrogen fertilizer in the organic form he
is usually able to maintain a ertility level sufficient for good yields. Some
cultural. practices can be util zed to reduce leaching from the plant bed. Table 1
shows the effect o inorganic fertilizer placement on concentrations of soluble
salts in various p rts of the plant bed during the growing season. Potassium and
nitrate levels fol wed the trend of soluble salts and are not shown. Fertilizer
was banded in the bed center at depths of one or five inches below the soil surface.
Later in the season the largest amounts of salts, potassium, and nitrates were
present in the plan bed with the upper placement of fertilizer. Preliminary trials
have indicated that increasing the height of the plant bed decreases leaching
because of the long period of irrigation required to saturate the plant bed.
Supplying part of th fertilizer in a slowly soluble form also should reduce leaching.
This is demonstrated in Table 2 where the use of urea, uramite, and sludge resulted
in higher levels of 4 and NO3 in the top six inches of the plant bed. Double
cropping of these sam beds with sweet and field corn, okra, and squash gave greater
growth and production where the original fertilizer was derived from urea, uramite
or sludge. Since str berry fruit production was halted on April 1 in these trials,
the growth of the sec nd crop is indicative of the amount of fertilizer remaining
for the U-Pick strawbe ry crop. Care must be taken not to supply more than 50% of
the nitrogen fertilize from slowly soluble nitrogen sources since nitrogen release
may be too slow for go d production especially during a long cold period.
Soil moisture lev If placement of fertilizer is in the upper portion of the
plant bed, the soil moi ture level in the area surrounding the fertilizer band
should be kept suffice tly high. In addition, high beds require more irrigation to
keep the soil moist tha do low beds. If the moisture around the fertilizer band
falls to a low level, t en the soil nutrients may not be available to the plant.
This will result in redu ed production. The use of seep irrigation in southern
Hillsborough and northern Manatee counties on strawberries permits precise control
of soil moisture except during periods of freezes and after transplanting when
overhead irrigation is r quired. Because of the high rates of overhead irrigation
required at transplanting and for frost protection, these growers must also use
cultural practices which control leaching.
Rates, theoretical. The amount of fertilizer used in producing 2400 flats of
fruit per acre is about 4 Ibs. of nitrogen and 40 lbs. of potassium In addition
a large healthy plant must be grown to produce the fruit. Generally the weight of
all the plant parts exclud g fruit produced in a season is less then one pound per
plant. This would require about 50 to 70 Ibs. of nitrogen and potassium per acre.
Therefore, a theoretical t tal of 90 to 110 lbs/acre of nitrogen and potassium are
required to produce the pl t and 2400 flats of strawberries. Another 1000 flats
could be produced with only 17 additional lbs. of nitrogen and potassium. Rates,
actual. However, it appear that strawberries produce best yields when high levels
of soil nitrogen and potass um are available to the plant. In a two season study at
the Agricultural Research Ce ter, Dover best yields were correlated with 600 ppm
pot:a-sium and 1000 ppm nitra e with a saturated paste extract soil test and based on
a soil moisture content one- alf that of saturation. These levels are fairly high.
Strawberries may yield quite well at considerably lower nutrient levels than this,
but effort should be expende to retain as high a level of fertility in the plant
bed as possible.
planting date and chilling
Planting date. The plan ng date of the strawberry transplant in the fruiting
field can effect the plant siz earliness, and even the total yield. The optimum
planting date needs to be dete ned for each variety since each variety has its own
optimum planting date. Trials over three seasons were conducted at ARC, Dover to
determine the optimum planting date for 'Tioga' transplants from California and
Florida. The results of these trials are summarized in Table 3. The early yields
tare reduced by delaying the pl ting date to November 1, and if transplants were not
et until November 15, the seas nal yields were reduced. There was no difference
between California or Florida p ants in yield. However, California plants produced
ery lor yields when set on Nov mber 15. These plants had 30 days of chilling and
were mainly vegeta ive during the fruiting season.
Plant chilling Chilling of local 'Tioga' plants will effect the growth and
fruiting response. Plants with 0, 15, and 30 days of chilling at 36F were set in
the fruiting field n October 1, October 15, and November 1 during two seasons at
ARC, Dover (Table 4 The setting of plants on November 1 reduced January yield as
it did in the above trials, but planting dates did not effect seasonal yield.
Chilling for 30 days reduced early and seasonal yield. These plants grew very large
and produced many ru ers. Fifteen days of chilling did not reduce early yields
when compared to tho e plants which received no chilling, and seasonal yields were
the highest. Chilli g generally gives vigor to the plant, but if chilling continues
too long the plant w 11 remain vegetative. Vigorous plants are desirable in the
fruiting field but a balance must be maintained between vegetative growth and fruiting
which will give great st fruit production. For 'Tioga' plants in central Florida,
15 days of chilling a pears to be optimum.
Some of the impor ant aspects of managing strawberries at transplanting are
1. Use healthy ematode free transplants.
2. Chill Tioga p ants 15 days and transplant before the last of October.
3. Reduce fertil zer leaching as much as possible in the plant bed by placing
banded fertile zer in the upper portion of the bed. Use fairly high plant
beds and slow y soluble fertilizer (25 to 50% of total) if leaching is a
4. Apply about 20 pounds per acre of nitrogen as N, potassium as K, and
phosphorus as 205. Vary the amount depending on degree of leaching
5. Apply micronut ients if you have had problems in past years or if planting
on new land.
6. Provide fertili er to the small transplant until it is able to feed from
that supplied i bed.
7. Retain the heal hy foliage on the transplant and keep it there by overhead
irrigation afte transplanting until the plant is established. Apply only
sufficient wate to keep foliage in good condition.
Table 1. Effect of fertile zer placement on soil soluble salts, in ppm in 3 areas of
the bed and at 3 soil d pths when sampled at 3 periods during the growing season.
1-4-68 2-29-68 4-15-68
Dep-th Ri M C R C R C
inches -Soluble salts2
i inch placement
0-2 2030 7390 19365 1015 3785 10140 630 7200
2-4 1050 3085 11825 600 1520 4425 480 6975
4-8 495 2035 4700 320 795 1095 310 3590
5 inch placement
0-2 875 2700 4240 745 970 1380 280 1330
2-4 545 2265 3155 680 495 1085 280 1600
4-8 520 2075 3310 870 415 825 255 1440
1Area of bed where soil sample was taken. R-In the plant row, M=One half the distance
between row & center of bed, =Center.
2Soil zests were from saturate extract solutions.
Table 2. Eff ct of fertilizer- source-on retention of ammonia Nl4 and
nitrate NO in the top six inches of soil1.
element SAN2 AN ANN U UN UA TAN SP
NH4 411 307 332 593 673 62 109 10
N03 760 669 588 562 514 278 84 50
N114 10 4 5 7 6 4 25 3
NO3 384 118 283 311 567 358 370 31
NH4 14 1 4 6 8 18 1 3
N03 162 33 46 33 226 187 89 5
-Soil tests were from saturated extract solutions.
2SAN = nitrogen rived equally from sludge and ammonium nitrate.
AN = nitrogen d rived from ammonium nitrate
ANN = nitrogen d rived from ammonium nitrate with nitrification inhibitor
U = nitrogen d rived from urea
UN = nitrogen de ived from urea with nitrification inhibitor added.
UA = nitrogen de ived from uramite
UAN = nitrogen de ived from uranite with nitrification inhibitor added.
SP = Fertilizer .upplied by twice weekly spraying of 'Nutri-leaf' at 10
The nitrification i hibitor was to slow down the conversion of ammonia to
nitrate in the earl part of the season.
Liable 3. Effect of plan ing date and source on yield for three seasons.
Jan. Feb. Mar. April Seasonal
Planting date lbs/acre
Oct. 15 29741 4028a2 5380a 3008a 15390a
Nov. 1 832 4289a 4896a 4688a 14705ab
Nov. 15 190 2886b 4212a 3905a 11193b
Fla. 1106 4528a 5622a 3006b 14262a
Ca. 1606 3526b 4777a 4958a 14867a
January data not analyzed because many plots had no yields.
Numbers in a column within planting date or source and followed by same letter are
not significantly different at 5% level.
Table 4. Effect
yield for two
o planting date
and chilling of transplants prior to setting on
Jan. Feb. Mar. April Seasonal
Planting date lbs/acre
Oct. 1 16171 4003a2 6519a 3822a 15961a
Oct. 15 1581 3548a 7802a 4074a 17005a
Kov. 1 785 4529a 5681a 5756a 16751a
0 1721 5151a 5888a 2777b 15537b
15 1866 5410a 7000a 3946b 18222a
30 396 1519b 7114a 6929a 15958b
1January data not anal zed because many plots had no yields.
2Numbers in a column wl thin planting date or days chilled and
letter are not signifi antly different at 5% level.
followed by same
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