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Bitter melon Luffa Long bean

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Nitr

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)

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.

IntroductionAsian 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