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Gcs Central Science
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GULF COAST RESEARCH & EDUCATION CENTER OCT 25 1989
IFAS, UNIVERSITY OF FLORIDA
5007 60th Street East U y of
Bradenton, FL 34203 university of Florida
Bradenton GCREC Research Report BRA1989-19 September 1989
BED WIDTH EFFECTS ON PERFORMANCE OF MICRO IRRIGATED VEGETABLES
D. N. Maynard and G. A. Clark1
Vegetables in West Central Florida are typically grown on raised beds that
are 30 to 36 in. wide. A wide bed is required for utilization of the
nutrient gradient production system. Concentrated bands of fertilizer are
placed in shallow grooves near both shoulders of the bed, and the wide bed
is necessary to insure appropriate soluble salts concentrations in the bed
center where the crop is planted.
When liquid fertilizer is injected into the micro irrigation system, the
need for a wide bed for fertilizer management is circumvented. In
addition, we have noted that in sandy soils, only the center portion of a
well-managed, micro-irrigated wide bed is wetted. Accordingly, growth is
restricted to the wetted zone of the bed.
With this background, this experiment was planned with the objective of
determining the response of several vegetable crops grown on 16, 24, and
32-in. wide beds with micro irrigation and N and K fertigation.
Materials and Methods
Soil in the experimental area was sampled before fertilization and
analyzed by the IFAS Extension Soil Testing Laboratory: pH = 7.3 and
Mehlich I extractable, P = 26, K = 16, Mg = 112, Ca = 592, Zn = 9.06, Cu =
2.26, Mn = 2.72 ppm.
The soil at the experimental site was an Eau Gallie fine sand (sandy,
silicaceous, hypothermic Alfic haplaquod) with a spodic horizon at 3 ft
and was prepared in late January 1989. Beds were formed, 0-1-0 lb N-P205-
K20 per 100 linear bed feet (Ibf) was incorporated, and the soil fumigated
with methylbromide:chloropicrin (67:33) at 2.1, 1.6, and 1.0 lb/100 Ibf
for the 32, 24, and 16-in. beds, respectively. The beds were pressed and
micro-irrigation tube [(Turbulent Twin Wall, Chapin Watermatics, Inc.) 8
mil thick, with a delivery rate of 0.5 gpm/100 ft at 10 psi] was
positioned 3-inches deep and 4-inches off the bed center before the black
polyethylene mulch was applied. Plots that were to be planted with pepper
had the tube positioned at the center of the bed. The final beds were 32,
24, or 16-in. wide and 8-in. high, and were spaced on 5-ft centers with
drainage ditches every 40.5 ft with six beds between ditches.
1Professor of Vegetable Crops and Assistant Professor of Agricultural
Vegetables (Table 1) were direct-seeded or transplanted on March 2 in
holes punched in the polyethylene. Each plot was replicated four times in
a randomized, complete block design. Analysis of variance was done on the
resulting data and regression analysis was made on statistically
significant data. Weed control in row middles was by cultivation.
Pesticides were applied as needed for control of worms (Bacillis
thuringiensis), sweetpotato whiteflies and aphids (insecticidal soap), and
foliar diseases (mancozeb).
Tensiometers were placed 6-in. deep between the irrigation tube and plant
row in the tomato plots and irrigation was scheduled to maintain soil
water potential levels at or above -lOkPa (Fig. 1) resulting in the
cumulative volumes of irrigation applied during the experimental period
(Fig. 2). Daily irrigations were divided into multiple cycles so that
each application was maintained within the top 10 in. of soil. Total
water application for each vegetable is shown in Table 2.
Fertilization with N and K was by daily injection of a 4-0-8 N-P205-K20
solution through the micro-irrigation tube. N and K fertilization for
each vegetable are shown in Table 2.
Vegetables were harvested at appropriate market maturity for each crop.
Where available, U.S. Grade Standards were used to separate marketable and
cull fruit. Marketable cucumber and squash fruit were counted and the
number of fruit multiplied by a previously determined factor to obtain
weight. For all of the other vegetables, marketable fruit were counted
and weighed. Soluble solids determinations were made on muskmelon and
Results and Discussion
Temperature and rainfall during the experimental period deviated somewhat
from the 33-year averages (2) at the Gulf Coast Research & Education
Center (Table 3). March temperatures were considerably higher than normal
and the entire period was drier than normal.
Although there was a tendency for yields to be highest from vegetables
grown on the 32-in. wide beds, the only significantly higher yield on the
widest beds was in summer squash (Table 4). For the most part, yields
considerably exceeded state average yields (1). For example, watermelon
yield was almost four times, and cucumber yield was more than twice the
reported state average yield. Eggplant was the only crop where data is
available that had a lower yield than the state average. This may have
been due to a severe infestation of sweetpotato whitefly that could not be
adequately managed with the general-purpose pesticides available for use
in multi-crop areas.
Fruit size provides a good measure of stress since fruit size is a very
responsive parameter. Average fruit weight was not affected by bed width
(Table 5) suggesting that plants growing on narrow beds are not stressed.
Another indication of stress would be lowered soluble solids concentration
in melon fruit, and that did not occur on narrow beds (Table 6). Soluble
solids were lower than in other field plots in the same season where
sweetpotato whitefly control was better.
From the results of this study, it appears that yields and quality of
vegetables would not be compromised by reducing the bed width of micro-
irrigated crops, however, additional experiments must be conducted before
final conclusions can be made. Associated benefits of narrower beds are
use of less polyethylene mulch and reduced disposal requirements at the
end of the cropping cycle, and energy requirements for bed preparation and
fumigant requirements are lower with narrow beds. If field drainage
conditions permit, beds can be spaced closer, thereby increasing bed feet
per acre. A potential disadvantage if bed spacing is unchanged is that
there is more row middle area that requires weed management. In addition,
equipment modifications would be required. There were some crop
management problems; e.g. staking, crops falling over, and lack of space
for melon fruit on the 16-in. wide bed. It appears that the 24-in. wide
bed provides a good alternative for growers interested in testing narrower
beds for micro-irrigated vegetables.
The information contained in this report is a summary of experimental
results and should not be used as recommendations for crop production.
Where trade names are used, no discrimination is intended and no
endorsement is implied.
1. Anonymous. 1989. Florida agricultural statistics. Vegetable
summary 1987-1988. Florida Agricultural Statistics Service, Orlando.
2. Stanley, C. D. 1988. Temperature and rainfall report for 1987.
GCREC Res. Rept. BRA1988-11.
Table 1. Varieties, establishment, plants per plot, in-row spacing, harvest period, and number of
harvests of vegetables grown on beds of various widths with micro-irrigation,
Plants/ Spacing Harvests
Vegetable Variety Establishmentz plot (ft.) Harvest Period (No.)
April 20-May 12
May 1-June 8
May 21-May 26
May 15-June 8
April 10-May 5
May 9-June 7
May 5-June 7
May 31-June 9
May 24-May 31
ZS = direct seeded, T = transplanted.
YTwo rows per bed.
Table 2. Nitrogen, potassium, and water application rates for vegetables
grown on beds of various widths with micro-irrigation.
N K20 Water
Vegetable (lb/A)z- (gal/1000 Ibf)
Cucumber 148 296 21,750
Eggplant 200 400 38,700
Muskmelon 181 362 29,925
Pepper 200 400 38,700
Squash, summer 127 254 17,850
Tomato 200 400 38,025
Tomato, cherry 200 400 38,025
Watermelon 200 400 39,375
Watermelon, icebox 194 388 33,300
ZAcre = 7260 linear bed feet.
Table 3. Mean temperature and rainfall at the Gulf Coast Research &
Education Center from March 1, 1989 to June 9, 1989 and 33-year
Average Daily Temperature (OF)
1989 33-year average Rainfall (in.)
Month (date) Max. Min. Max. Min. 1989 33-year average
March 80 59 76 54 2.97 3.39
April 83 60 82 60 1.38 1.59
May 88 64 88 66 2.44 3.14
June (1-9) 92 72 91 71 0.94
Table 4. Marketable yields of vegetables grown on beds of various widths with micro-irrigation.
Bed Width (in.)
16 24 32
Vegetable Unit Marketable yield (units/A) Significancez
Cucumber 55-lb 1 1/9 bu. 949 888 1018 NS
Eggplant 33-lb bu. 532 547 568 NS
Muskmelon cwt. 238 248 277 NS
Pepper 28-lb bu. 687 897 853 NS
Squash, summer 42-lb bu. 346 367 417
Tomato 25-lb carton 1516 1878 1606 NS
Tomato, cherry 15-lb flat 2845 2935 3032 NS
Watermelon cwt. 576 693 715 NS
Watermelon, icebox cwt. 526 526 600 NS
zNS = not significant, = significant at the 5% level.
Table 5. Average fruit weight of vegetables grown on beds of various
widths with micro-irrigation.
Bed Width (in.)
16 24 32
Vegetable Average fruit wt (lb.) Significancez
Eggplant 0.6 0.7 0.6 NS
Muskmelon 2.4 2.5 2.7 NS
Pepper 0.3 0.4 0.4 NS
Tomato 0.5 0.4 0.4 NS
Tomato, cherryY 5.6 6.3 5.8 NS
Watermelon 21.8 25.1 23.5 NS
Watermelon, icebox 8.5 7.5 8.1 NS
zNS = not significant.
YWeight of 100 cherry tomato fruit.
Table 6. Soluble solids of melon fruit grown on beds of various widths
Bed Width (in.)
16 24 32
Vegetable Soluble solids (%) Significancez
Muskmelon 10.5 9.9 10.4 NS
Watermelon 10.1 10.6 10.6 NS
Watermelon, icebox 11.2 11.3 11.5 NS
zNS = not significant.
80 100 120 140 160
Day of Year
Irrigation schedule for micro irrigated vegetables
grown on 16, 24, or 32-inch wide beds. Spring 1989.
80 100 120 140 160
Day of Year
Figure 2. Cumulative irrigation of micro irrigated vegetables grown
on 16, 24, or 32-inch wide beds. Spring 1989.