Poster presentation for 2016 NACAA meeting, Little Rock, Arkansas.

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Numberoffruits(lbs)
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Weightoffruits(lbs)
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Bitter melon 1430 1610 1900
Luffa 430 795 810
Long bean 477.5 520 537.5
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NitrateContent(ppm)
Rates of Nitrogen Applied (lb/ac)
Bitter melon Luffa Long bean
Graph 1. Petiole nitrate levels at flowering.
Graph 2. Number of luffa fruits per N rate.
Graph 3. Yardlong bean fruit weight per N rate.
Asian vegetable acreage is increasing in Florida as growers seek
alternative crops to stay competitive. However, optimal fertilizer
applications to increase grower returns and minimize
environmental impacts have not been established for these crops.
This project aims to determine optimal nitrogen (N) rates for
selected Asian vegetables by evaluating the effect of N rates on crop
yield and petiole nitrate levels. Field trials were established in
Hastings, Florida on July 29, 2015, using bitter melon (Momordica
charantia L.), yardlong bean, (Vigna unguiculata subs.
sesquipedalis), and luffa (Luffa cylindrica (L.) Roem). Fertigation
through drip irrigation was used to apply N rates of 50, 100, and
150 lbs per acre using an 8-0-8 liquid fertilizer to the plantings that
were randomly assigned with 4 replications. Petiole nitrate levels
were determined using a HORIBA LAQUA Twin nitrate meter
(Model: B-741), with sap measured at flowering, early fruiting, and
late fruiting. Fruit number and weight were measured at 50-89 days
after planting. Petiole nitrate levels and yields were highest with
150 lb/ac N and lowest with 50 lb/ac N; however, significant yield
increases were only seen with bitter melon. Luffa had a similar yield
tendency but with more mixed results. Yardlong bean is an effective
nitrogen fixer and did not have much difference in yields. Field
evaluations will be repeated with improvements in 2016.
Abstract Experimental Methods
Treatments were three nitrogen rates of 50, 100,
and 150 lbs per acre, applied via drip irrigation
using International Liquid Mix (8-0-8).
On-farm field trials were planted in Hastings,
Florida on July 29th, 2015, using the following
crops: Bitter melon, F1 Hybrid Green Skin Bitter
Melon (Fig. 1), Luffa, Angle Type Jiao Gua (Fig. 2),
and Yardlong bean, White Skin Bai-Long (Fig. 3).
Plantings were in 30 ft beds with 6 feet spacing for
each treatment. Twelve randomly assigned plots
were established per bed with four replications.
Site Preparation:
Petiole nitrate levels and yield were highest with 150
lb/ac nitrogen and lowest with 50 lb/ac nitrogen, which
was expected (Graph 1). The three main findings of this
study were that (1) bitter melon had significant yield
increases with N rates: 150 lb/A N had the greatest yield
and 50 lb/A the lowest, (2) luffa had a similar yield but
only significant in fruit number (Graph 2), and (3) yardlong
bean is an effective N fixer and didn’t have much
difference in yields with N rates (Graph 3). Data warrants
further investigations. Improved field trials will be
evaluated in 2016.
Results and Discussion
Acknowledgements:
Thank you to Dr. David Liu, Plant Nutrition Extension Specialist
at UF/IFAS, for providing leadership during this project.
Introduction
Asian vegetables are emerging
crops in Florida with a high
potential to benefit both growers
and consumers. More than 3,000
acres are grown in the Hastings
area of St. Johns County, Florida.
However, research based
recommendations for the best
management practices (BMPs) of
these crops have not yet been
established.
Figure 3. Yardlong bean plantings Figure 2. Luffa fruit
Figure 1. Bitter melon fruit
Harvest /Yields
Data Collection:
Petiole Nitrate Levels
Nitrate content in the sap was measured using LAQUA Twin
nitrate meter (Fig. 4). The petiole sap nitrate was measured
three times: flowering, early fruiting and late fruiting which
were approximately 35, 55, and 70 days after planting,
respectively.
Fruit number and weight were recorded for each plot
separately at harvesting. Harvesting occurred first at 50
days after planting (dap) and continued after 54, 67, 75, 82
and 89 dap.
Data Analysis:
The PROC GLM command in SAS was used to conduct
the analysis of variance for fixed effect of treatment
rates i.e. nitrogen application rates on petiole nitrate
level and yield.
Figure 4. LAQUA Twin Nitrate Meter for measuring plant nitrate levels
Development of Optimal Nitrogen Applications for Selected Asian Vegetables
Bonnie C. Wells, DPM, Extension Agent II, UF/IFAS Extension St. Johns County, St. Augustine, Florida, 32092