Establishing an Organic Watermelon Industry in South Carolina

View the project report

Commodities

• Fruits: melons

Practices

• Crop Production: crop improvement and selection, plant breeding and genetics
• Pest Management: integrated pest management
• Soil Management: soil quality/health

Controlling weeds and diseases in organic watermelon production is difficult. Certain varieties of watermelon have been bred for resistance to key pathogens and insects, yet no type of inherent resistance mechanisms exists in crops that will directly resist weed infestation. Furthermore, there is no substantial resistance in watermelon to certain races of Fusarium wilt a devastating disease in watermelon production.

(ASD) has been shown to suppress certain weed species and soil-borne pathogens. Furthermore, preliminary data taken from the USDA-ARS, United States Vegetable Laboratory (USVL) in Charleston, SC by Dr. Cutulle and USVL scientists indicate that carbon source influences weed and soil borne plant pathogen (or disease) suppression. ASD works by driving the soil into an anaerobic state for several weeks, thus reducing or eliminating the aerobic microorganisms. ASD is facilitated by amending the soil with a high carbon source, followed by sealing the soil in an impermeable plastic mulch and driving the soil into an anaerobic state by saturating the soil under the mulch with water. However, a limiting factor for facilitating ASD is the cost of the carbon source.  There is a need to evaluate several carbon sources from on farm waste streams or other waste on their ability to facilitate ASD.

In addition to the large volumes of viable carbon sources generated through agro-industrial waste streams, a second issue significantly burdening watermelon growers is the ever-increasing cull pile correlational to consumer-based demands (and thus retail and wholesale demand) for flawless perfection and shelf life demands in perishables. Only a percentage of a grower’s conventional and organic crop – especially in specialty crop markets – is flawless enough to meet the industry’s highly rigid retail and consumer-driven specifications. This pushback of product, back into agricultural systems before ever leaving the farm or packinghouse is costly to all of us when considering that global food production contributes an estimated 19 – 29% of greenhouse gas (GHG) emissions worldwide and accounts for 70% of global fresh water use. A grower’s best  innovative crop inputs and valuable resource allocation, can quickly and arbitrarily pile into unsustainable losses of floating catastrophic whims due to the highly perishable nature of most specialty crops mounded onto a volleying availability of buyers, fluctuating market demand, the onset of an insufficient price to justify harvest, and/or unmarketable aesthetic attributes.

Finally, an obstacle with producing more watermelon in the coastal regions of South Carolina is saltwater inundation on farmland. Preliminary saltwater screening greenhouse studies with watermelon cultivars, experimental PIs, and breeding stock identified germplasm that had increased saltwater tolerance relative to leading commercially available watermelon cultivars. These germplasm accessions have the potential to be grown on land where the salinity of the irrigation sources make it difficult to grow most crops.

This proposal will integrate ASD treatments using carbon waste streams with salt tolerant germplasm grown in partial salt-water agro-ecosystems. Ideally, this will provide a foundation for increasing organic watermelon production in South Carolina.  

1. Determine if there is a differential response of the USDA watermelon germplasm panel and commercially available cultivars to soil that has underwent ASD. This objective will involve screening 20 watermelon PIs and 10 root stocks for reactivity to ASD at multiple transplant timings. The initial screening will use a standard carbon source that has been shown to facilitate ASD. However, a follow up experiment will explore the use of local carbon sources that have been identified in objective 2. A bucket ASD trial with selected PIs and root stocks from the first study will be conducted with carbon sources identified by agents, evaluators and growers in objective 2. The application of rhizobacteria to colonize ASD treated soil will be explored in this objective as well.
2. Quantify Carbon and Nitrogen in carbon waste streams to include brassica waste, sweetpotato waste from processing facilities, brewer’s yeast waste, potentially others local carbon sources. We will sample local carbon waste streams and other local carbon sources and send away for analysis. We will follow the suggestions of the project evaluator, extension agents and local growers if alternate or more carbon sources should be evaluated.
3. Conduct field trials in partial saltwater agro-ecosystems with watermelon germplasm that have exhibited tolerance to saltwater irrigation in preliminary greenhouse studies. Evaluate weeds, disease, yield, and soil health. Since the germplasm collection has increased since we screened for salt tolerance in Charleston multiple years ago, we will also conduct a preliminary germplasm germination screening with different saltwater concentrations on newly acquired/developed watermelon PIs. This screening will include 10 new PIs as well as salt tolerant and sensitive PIs from the initial screening.
4. Conduct field trials using ASD standard carbon sources as well as carbon waste streams side by side. Evaluate weeds, disease, yield, and soil health. This study will include combinations of different Plasticulture materials, carbon sources, and watermelon germplasm. This will determine the functionality of these carbon waste streams for facilitating ASD in field scenarios.
5. Integrate ASD treatments into partial saltwater agro-ecosystems in on farm trials and at station trials. This will combine plasticulture, carbon source, and germplasm treatments. This objective is to determine the impact of integrating all concepts in this grant on weed ecology, soil health, and productivity of partial saltwater agroecosystems that have undergone ASD.

          All Objectives will be done in collaboration with the USDA-USVL Dr. Kousik and Dr. Levi (Letter of Commitment-Matt-AL)