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?5/-00 UNIVERSITY OF
Institute of Food and Agricultural Sciences
Gulf Coast Research and Education Center
5007 60th St. E., Bradenton, FL 34203
Bradenton GCREC Research Report
BRA-1995-10 (March 1995)
YIELD RESPONSE OF 'SENATOR' ZUCCHINI TO
SEAWEED SPRAY, MICRONUTRIENT AND
APR 20 19
Bradenton GCREC Research Report BRA1995-10
YIELD RESPONSE OF 'SENATOR' ZUCCHINI TO SEAWEED SPRAY,
MICRONUTRIENT AND POTASSIUM RATES
A. A. Csizinszky'
Gulf Coast Research and Education Center
University of Florida, IFAS
5007 60th Street East
Bradenton, FL 34203
A study was conducted at the Gulf Coast Research and Education Center, Bradenton
in the spring 1993 to evaluate the yield of 'Senator' zucchini squash at three
foliar-applied seaweed spray rates and two micronutrient and two N and K rates.
Materials and Methods
The experiment was conducted on an Eau Gallie fine sand. Soil samples taken
prior to land preparation, were analyzed at the University of Florida's
Analytical Research Laboratory at Gainesville and had a pH of 6.73 and 64.0 P,
8.4 K, 773 Ca, 111 Mg, 2.2 Cu, 7.2 Fe, 3.5 Mn, 5.1 Zn, 1.0 NH4, and 0.25 NO3 (in
Experimental design was a split-split plot arranged in a randomized complete
block and replicated four times. Main plots, 84-ft long and 5-ft wide, were
three seaweed foliar spray rates; sub-plots, each 42-ft-long and 5-ft wide, were
two micronutrient rates, and sub-sub plots, each 21-ft long and 5-ft wide, were
two N and K rates. In two of the main plots, plants were sprayed with seaweed
sprays at 112 fl oz (Sl) or at 168 fl oz per acre (S2). In the Sl plots, sprays
were applied four times during the season: 12 and 26 Apr., and 10 and 17 May at
28 fl oz per application. In the S2 plots, plants were sprayed seven times: on
12 and 26 Apr., 10, 17, and 24 May and 1 and 8 June, at 24 fl oz per acre per
application. In the third main plot, plants were sprayed with water only which
served as a control (SO). The seaweed concentrate from Acadian Seaplants, Ltd.,
Canada (Table 1) was diluted in 88 gallons of H,0. Sprays were applied by a
portable backpack sprayer at 40 psi. A biodegradable sticker/spreader was added
to the spray to facilitate better spray cover and retention.
In the sub-plots, plants were grown with residual (Mo) or with added
micronutrients (Ml). Micronutrient source was an F503 oxide at 21 lb per acre
that provided (in lb per acre) 0.63 B, 0.63 Cu, 3.76 Fe, 1.57 Mn, 0.04 Mo, and
1.46 Zn. The two sub-sub plots, from a 15-0-20.8 (N-P-K) source, received either
174 N and 200 K (Fl) or 261 N and 300 K lb per acre (F2).
Phosphorous from a 0-8.7-0 (N-P-K) superphosphate was applied at 46 P per acre
for all treatments. The superphosphate and the micronutrients were applied in
a 6-inch wide band on the false bed and the N and K were placed in a 2-inch deep
narrow furrow in the bed center of the 32-inch wide and 8 inch high beds that
were formed on 5-ft centers. Soil was fumigated with 66.6% methylbromide and
33.3% chloropicrin at 213 lb per acre, then covered with 1.25 mil thick
polyethylene. Two weeks later, on 29 March, seeds of 'Seneca' zucchini were sown
in holes punched through the mulch in double rows on the bed at 24-inch within
and 12-inch between row spacing. Land was irrigated by the seepage irrigation
system. Pesticides, labeled for use on zucchini squash, were applied weekly.
Soil samples for macro and micro-element analyses were taken from each sub-sub
plot immediately after sowing and after last harvest. Petiole samples for macro
and microelemental analyses were collected on 19 May and 8 June, and fruit
samples on 19 May. Chemical analyses were carried out at the Analytical Research
Laboratory, University of Florida, at Gainesville. Fruits were harvested three
times per week for 6 weeks beginning on 6 May and ending on 16 June. During the
first week the average weight of 150 marketable fruits were measured from each
treatment. In subsequent harvests, weight of marketable fruits were calculated
by multiplying the number of marketable fruits harvested by the average fruit
weights. Marketable yields in this report are tabulated as weekly totals for the
6 weeks of the harvest season and yields of the first 2 weeks are considered as
early yield. All data were analyzed by analysis of variance (ANOVA).
Results and Discussion
Due to the dry weather during May and June, fungus damage was not observed on the
plants and on the fruits. As a result of the favorable weather, the harvest
season was approximately 2 weeks longer than in previous years. Phytotoxicity
was not apparent on seaweed treated or on control plants.
Seaweed spray rates had little or no effect on zucchini yields (Table 2). In the
first weekly harvest, with the 112 fl oz/acre seaweed spray (Sl) yields were
lower (127 ctn/A) than with 116 fl oz/acre seaweed spray (S2) (143 ctn/A) or with
water control (SO) (141 ctn/A). Plants with the S1 spray treatment tended to
have lower yields throughout the season than with the S2 or SO treatment, but
yield differences were non-significant.
Zucchini yields with the two micronutrient and N and K rates were similar at all
harvest dates (Table 2). Among the interactions, seaweed spray and micronutrient
(SxM) and seaweed spray and N and K rates (SxF) had significant effects on
zucchini yields (Tables 2 and 3). Yields with the S2 Mo treatment were higher
(720 ctn/A) than with the SIM1 (666 ctn/A), SOM1 (628 ctn/A) and SIMo (565 ctn/A)
treatments, but similar to the SOMO (683 ctn/A) and S2M1 (677 ctn/A) treatments
The combination of 168 fl oz/acre seaweed spray (S2) with the higher N and K rate
(F2) resulted in a higher seasonal total fruit yield (734 ctn/A) than any other
spray and N and K rate combination (Table 3).
In the soil, macro and microelement concentrations at the end of the season (71
DAP) were similar with all treatments (data not presented).
In the petioles, macro and microelement concentrations were similar with the
three spray rates (data not presented). Micronutrient rates at 71 days after
planting affected tissue B concentrations only. Boron concentration in the
petioles was 43.4 ppm with added (Ml) micronutrients and 40.9 pm with residual
(M2) micronutrients (P<0.05). Nitrogen and K rates affected only dry matter, N,
K, and Mn concentrations in the petioles. Dry matter was lower while N, K, and
Mn concentrations were higher with the higher N and K rate. Dry matter content
was 7.49% and 6.86%, N concentration was 0.78% and 0.95%, K was 1.73% and 2.43%
and Mn 43.7 ppm and 50.5 ppm, respectively, for F1 and F2 N and K rates (P
In fruits, dry matter and macro- and micronutrient concentrations were similar
with all treatments.
Zucchini yields in this study were much higher than the average squash yields of
276 bu per acre yields for Florida (Florida Agric. Statistics, 1993). The reason
for the higher yields may be the long harvest season, cultivars, and production
system and market conditions.
In summary, plants treated seven times during the season at a rate of 24 fl oz
per acre seaweed concentrate in 88 gallons of water for a total of 168 fl oz per
acre seaweed concentrate for the season, in combination with 261N and 300 K lb
per acre gave higher seasonal marketable yield than seaweed sprayed or water
treated control treatments with 176N and 200 K lb per acre. All other seaweed
spray treatments with or without added micronutrients had similar or lower yields
than water control.
Note: The use of trade names in this publication does not imply either
endorsement or criticism of these products by the author or the University of
Florida Agricultural Statistics, Vegetable Summary 1992-1993. Fla. Agric.
Statistics Service, Orlando, FL.
Hanlon, E. A., and J. M. deVore. 1989. Chemical procedures and training
material. Fla. Coop. Ext. Ser. Circ. 812. Gainesville, FL.
Hanlon, E. A., G. Kidder, and B. L. McNeal. 1990. Soil, container, and water
testing. Fla. Coop. Ext. Circ. 817. Gainesville, FL.
United States Department of Agriculture. 1984. United States Standards for
Grades of Summer Squash. USDA Agric. Marketing Service, Washington, D.C.
Table 1. Composition of liquid Acadian
% (weight per volume)
zIn addition, the concentrate also contained undetermined amounts of plant
hormones (auxins, cytokinins, gibberellins), amino acids and carbo-
Table 2. Main effects and interactions of seaweed spray, micronutrient and N
and K rates on the cumulative yields of zucchini.
Treatment 1 1-2 1-3 1-4 1-5 1-6
Spray rate (S)z
So 141 275 420 585 606 655
S, 127 256 386 554 567 615
S2 143 276 431 607 645 699
LSDo.os0 13.5* ns ns ns ns ns
Mo 138 271 415 585 604 656
MI 136 267 410 579 608 657
LSDo.05 ns ns ns ns ns ns
N and K rate (F)W
F, 141 269 417 581 601 650
F 151 269 409 582 611 663
LDo.os5 ns ns ns ns ns ns
S xM ns *
S x F ns *
M x F ns ns ns ns ns ns
S x M x F ns ns ns ns ns ns
ZSo = water control; S, = 112 fl oz/A; S2 = 168 fl oz/A seaweed concentrate
YLSD is significant at the 5% (*) level or non-significant (ns).
XM = residual micronutrients only; Mi = 21 Ib/A F503.
WF = 174 N and 200 K; F = 261 N and 300 K Ib/A.
VInteraction of treatments is significant at the 5% level (*) level or non-
Table 3. Effect of two-way interactions on zucchini fruit yields (ctn/A).
Treatment S S' S2
Mo 683 abx 565 c 720 a
Mi 628 bc 666 b 677 ab
N and K rate
F. 641 bcx 644 bc 644 b
F2 670 b 586 c 734 a
zSpray rate: SO = water control;, S, = 112 fl oz/A; S2 = 168 fl oz/A seaweed
concentrate per season.
YMicronutrient rate: Mo = residual micronutrients only; M = 21 lb/A F503.
XMean separation by Duncan's Multiple Range Test, P 0.0.
WN and K rate: F, = 174N and 200 K; F2 = 261 N and 300 K Ib/A.
The Gulf Coast Research and Education Center
The Gulf Coast Research and Education Center is
a unit of the Institute of Food and Agricultural Sci-
ences, University of Florida. The Research Center
originated in the fall of 1925 as the Tomato
Disease Laboratory with the primary objective of
developing control procedures for an epidemic out-
break of nailhead spot of tomato. Research was ex-
panded in subsequent years to include study of sev-
eral other tomato diseases.
In 1937, new research facilities were established
in the town of Manatee, and the Center scope was
enlarged to include horticultural, entomological, and
soil science studies of several vegetable crops. The
ornamental program was a natural addition to the
Center's responsibilities because of the emerging in-
dustry in the area in the early 1940's.
The Center's current location was established in
1965 where a comprehensive research and extension
program on vegetable crops and ornamental plants is
conducted. Three state extension specialists posi-
tions, 16 state research scientists, and two grant
supported scientists from various disciplines of
training participate in all phases of vegetable and
ornamental horticultural programs. This interdisci-
plinary team approach, combining several research
disciplines and a wide range of industry and faculty
contacts, often is more productive than could be ac-
complished with limited investments in independent
The Center's primary mission is to develop new
and expand existing knowledge and technology, and
to disseminate new scientific knowledge in Florida, so
that agriculture remains efficient and economically
The secondary mission of the Center is to assist
the Cooperative Extension Service, IFAS campus
departments, in which Center faculty hold appropri-
ate liaison appointments, and other research centers
in extension, educational training, and cooperative
research programs for the benefit of Florida's pro-
ducers, students, and citizens.
Program areas of emphasis include: (1) genetics,
breeding, and variety development and evaluation;
(2) biological, chemical, and mechanical pest manage-
ment in entomology, plant pathology, nematology,
bacteriology, virology, and weed science; (3) produc-
tion efficiency, culture, management, and counteract-
ing environmental stress; (4) water management and
natural resource protection; (5) post-harvest physiol-
ogy, harvesting, handling and food quality of horti-
cultural crops; (6) technical support and assistance to
the Florida Cooperative Extension Service; and (7)
advancement of fundamental knowledge of disciplines
represented by faculty and (8) directing graduate
student training and teaching special undergraduate
" The Institute of Food and Agricultural Sciences,
University of Florida.
" A statewide organization dedicated to teaching,
research and extension.
" Faculty located in Gainesville and at 13 research
and education centers, 67 county extension
offices and four demonstration units throughout
D A partnership in food and agriculture, and natural
and renewable resource research and education,
funded by state, federal and local government,
and by gifts and grants from individuals, founda-
tions, government and industry.
" An organization whose mission is:
Educating students in the food, agricultural,
and related sciences and natural resources.
Strengthening Florida's diverse food and
agricultural industry and its environment
Enhancing for all Floridians, the application
of research and knowledge to improve the
quality of life statewide through IFAS exten-