Final report for LS22-369
Project Information
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.
- 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.
- 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.
- 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.
- 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.
- 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)
Cooperators
- - Producer
- - Producer
- - Producer
- - Producer
Research
ASD High Tunnel Sceening Studies
Initial studies were conducted to evaluate the response of watermelon germplasm to ASD. See table below that shows the impact of ASD on different watermelon cultivars. Plant vigar estimates are on a 1-10 scale with 10 being the highest.
|
Treatment |
Cultivar |
Plant vigor estimate (1-10) |
|||||
|
7 DAT |
14 DAT |
28 DAT |
|||||
|
Trial 1 |
Trial 2 |
Trial 1 |
Trial 2 |
Trial 1 |
Trial 2 |
||
|
ASD |
Powerhouse |
6.2 |
6.3 A-D |
6.8 AB |
6.8 A-C |
8.7 AB |
8.2 AB |
|
Non-ASD |
6.3 |
5.8 A-E |
6.2 A-D |
6.5 A-D |
5.7 D-J |
5.8 C-G |
|
|
ASD |
Extazy |
6.2 |
6.7 AB |
6.7 A-C |
6.8 A-C |
9.0 A |
8.0 A-C |
|
Non-ASD |
6.0 |
6.0 A-E |
5.8 A-E |
5.7 B-G |
5.8 D-I |
5.5 D-G |
|
|
ASD |
Exclamation |
6.3 |
6.5 A-C |
7.0 A |
7.2 AB |
8.5 A-C |
8.0 A-C |
|
Non-ASD |
5.7 |
6.0 A-E |
5.5 B-F |
5.8 A-F |
5.5 E-J |
5.8 C-G |
|
|
ASD |
Sangria |
6.2 |
7.0 A |
7.0 A |
7.3 A |
7.0 A-D |
8.8 A |
|
Non-ASD |
5.7 |
5.8 A-E |
5.8 A-E |
6.0 A-E |
5.3 E-J |
5.5 D-G |
|
|
ASD |
USVL-482 |
5.2 |
5.8 A-E |
5.3 C-G |
5.7 B-G |
7.5 A-E |
6.2 B-G |
|
Non-ASD |
5.5 |
5.7 B-E |
5.3 C-G |
4.7 E-H |
4.7 F-L |
4.8 D-G |
|
|
ASD |
Tri-X-313 |
4.8 |
5.2 B-E |
5.2 D-G |
5.3 C-G |
6.3 B-G |
7.3 A-D |
|
Non-ASD |
5.2 |
5.2 B-E |
4.5 E-G |
4.7 E-H |
5.0 F-K |
5.2 D-G |
|
|
ASD |
Dark Knight |
5.2 |
5.0 C-E |
5.0 D-G |
4.8 E-H |
4.7 F-L |
4.8 D-G |
|
Non-ASD |
4.7 |
4.7 DE |
4.5 E-G |
4.8 E-H |
4.0 G-L |
5.0 D-G |
|
|
ASD |
Sugar Baby |
4.8 |
5.5 B-E |
5.2 D-G |
4.8 E-H |
5.3 E-J |
5.2 D-G |
|
Non-ASD |
4.3 |
4.7 DE |
4.3 E-G |
4.2 GH |
4.3 F-L |
4.0 E-G |
|
|
ASD |
Fascination |
4.8 |
4.8 DE |
4.8 D-G |
4.7 E-H |
5.7 D-J |
5.0 D-G |
|
Non-ASD |
4.2 |
4.8 DE |
4.3 E-G |
4.5 E-H |
3.7 H-L |
5.5 D-G |
|
|
ASD |
USVL-351 |
4.5 |
4.8 DE |
5.2 D-G |
5.3 C-G |
6.5 B-F |
6.5 B-E |
|
Non-ASD |
4.3 |
4.8 DE |
4.5 E-G |
5.0 D-G |
4.7 F-L |
5.7 D-G |
|
|
ASD |
Calhoun Grey |
4.3 |
4.8 DE |
4.7 D-G |
4.8 E-H |
6.2 C-G |
5.7 D-G |
|
Non-ASD |
4.5 |
4.8 DE |
4.7 D-G |
4.7 E-H |
4.0 G-L |
4.0 E-G |
|
|
ASD |
Crimson Sweet |
4.3 |
4.8 DE |
4.8 D-G |
5.0 D-G |
5.8 D-I |
5.2 D-G |
|
Non-ASD |
4.5 |
5.0 C-E |
4.7 D-G |
4.8 E-H |
4.0 G-L |
4.0 E-G |
|
|
ASD |
Excursion |
4.0 |
4.5 E |
4.3 E-G |
4.3 F-H |
6.0 D-H |
5.5 D-G |
|
Non-ASD |
4.5 |
5.5 B-E |
4.7 D-G |
4.8 E-H |
3.7 H-L |
3.8 E-G |
|
|
ASD |
Melody |
4.2 |
4.3 E |
5.2 D-G |
5.0 D-G |
5.5 E-J |
6.5 B-E |
|
Non-ASD |
4.3 |
5.2 B-E |
4.5 E-G |
4.7 E-H |
4.3 F-L |
4.5 E-G |
|
|
ASD |
Black Diamond |
4.0 |
4.0 E |
4.5 E-G |
4.5 E-H |
5.2 E-J |
6.3 B-F |
|
Non-ASD |
4.3 |
5.0 C-E |
4.5 E-G |
4.7 E-H |
2.7 KL |
4.8 D-G |
|
|
ASD |
Top Guns |
3.7 |
4.0 E |
4.3 EG |
4.5 E-H |
5.0 F-K |
5.5 D-G |
|
Non-ASD |
4.5 |
4.8 DE |
4.5 E-G |
4.7 E-H |
3.5 I-L |
4.5 E-G |
|
|
ASD |
Ojjkayyo |
3.5 |
4.0 E |
3.7 G |
3.3 H |
4.8 F-K |
4.5 E-G |
|
Non-ASD |
4.5 |
5.0 C-E |
4.3 E-G |
4.5 E-H |
2.3 L |
3.0 G |
|
|
ASD |
Charleston Grey |
3.8 |
4.5 DE |
4.3 E-G |
4.5 E-H |
5.3 E-J |
5.8 C-G |
|
Non-ASD |
4.0 |
4.2 E |
4.0 F-G |
4.2 GH |
4.7 F-L |
3.8 E-G |
|
|
ASD |
Captivation |
3.5 |
4.7 DE |
3.8 F-G |
4.2 GH |
5.2 E-J |
5.2 D-G |
|
Non-ASD |
3.7 |
4.3 E |
3.8 F-G |
4.2 GH |
4.2 F-L |
4.0 E-G |
|
|
ASD |
Estrella |
3.3 |
4.3 E |
3.8 F-G |
4.2 GH |
3.7 H-L |
5.2 D-G |
|
Non-ASD |
3.8 |
4.8 DE |
4.0 F-G |
4.3 F-H |
3.3 J-L |
3.2 F-G |
|
|
p value |
|||||||
|
Treatment |
0.4890 |
0.4177 |
<0.0001* |
0.0009* |
<0.0001* |
<0.0001* |
|
|
Cultivar |
<0.0001* |
<0.0001* |
<0.0001* |
<0.0001* |
<0.0001* |
<0.0001* |
|
|
Treatment*Cultivar |
0.7247 |
0.0293* |
0.01* |
0.0011* |
0.0055* |
0.0014* |
|
Treatment and cultivar interaction were present in the trials so data for trial 1 and trail 2 presented separately (Table). Plants responded to ASD treatment at 7 DAT and phytotoxic symptoms were observed such as yellowing of leaves and stunted growth. No significant difference in treatments was present at 7 DAT in both trials. However, significant differences were detected in cultivars in
trial 1 and 2 at 7 DAT (p <0.0001). At 14 DAT, treatment, cultivation, and their interaction were statistically significant. Exclamation and Sangria had more plant vigor in both trials at 14 DAT compared to other cultivars. At 28 DAT, plants vigor was more evident in ASD treatment compared to Non-ASD treatment. Extazy had the highest plant vigor in trial 1 followed by Powerhouse, Exclamation, and Sangria. In trial 2, highest plant vigor was recorded in cultivar Sangria followed by Powerhouse, Extazy, and Exclamation. Treatment, cultivar, and their interaction were statistically significant at 28 DAT (Table). Overall, ASD improved the watermelon plant vigor significantly compared to Non-ASD treatment.
Description of Field Studies
ASD Work
A field study was conducted at the Clemson University Coastal Research and Education Center in Charleston, SC to specifically look at the impact of chicken manure + molasses (CM+M), and cotton seed meal (CSM) on grafted vs non-grafted watermelon yield. The study was designed in a randomized complete block design. The treatments were assigned as ASD with powerhouse non-grafted and Carolina strongback rootstock grafted to powerhouse. All treatments that went anaerobic removed the iron oxide paint from indicator of reduction in soils (IRIS) tubes and reduced yellow nutsedge counts when compared to the treatments that did not go anaerobic. At the time of watermelon harvesting, total number of yellow nutsedge counts were recorded as 65, 25, and 22 in control, CSM, and CM+M, respectively. Based on weed control and yield assessments, using CM+M to facilitate ASD is an ideal practice for growing organic watermelon in South Carolina.
Salinity Work
The issue of soil salinity as a major cause of poor soil health and crop yield loss has been of growing concern as climate change contributes to its effects. The objective of this research was to study the impact of increasingly saline soils on the relationship between grafted watermelons and yellow nutsedge, one of the major weeds in watermelon plasticulture. The seedless watermelon cultivar Melody was grown in a field after being grafted onto the C. maxima hybrid Carnivor and the C. amarus cultivar Carolina Strongback in addition to both a self-grafted and ungrafted control. The field was divided into four rows, which were irrigated with 0, 10%, 20%, and 30% dilutions of sea water for the duration of the experiment. A weed count was performed after one month and three months of irrigation. This demonstrated that salt had a significant effect on the total weed count at high concentrations, however the weeds demonstrated a much greater resistance to salt treatment than the watermelons in this trial. Based on this data, it is possible that salt intrusion events can contribute to increased weed related yield loss in watermelon crops.
Methods and Results for objectives 1-4 are listed in the powerpoints below.
For objective 5 we integrated the best treatments from the ASD objectives with best cultivar from the saltwater screening objective. The experiment was setup as a factorial with two carbon sources (best one from objectives 1-3 or no carbon source) x two irrigation sources (fresh water or 8mS salt water) for a total of 4 treatments replicated 4 times. We selected cotton seed meal as the carbon source at a rate of 6785 lbs per acre. The cultivar we selected was Melody non grafted as we determine that interestingly was no benefit with respect to salt tolerance or yield was observed when using a grafted rootstock, thus it makes sense economically based on our results to just use non-grafted Melody. The plot size was 30 feet in length on a three foot raised bed. 1500 lbs per acre of 10-2-8 nature safe fertilizer was applied pre-plant. ASD was initiated on July 30th 2025 and terminated on August 29th. Watermelon was transplanted one week after ASD termination. Watermelons were harvested in the end of November. The combination of saltwater treatment and ASD resulted in the best weed control program. In the bucket study thh combination of grafting, ASD and fresh water irrigation resulted in the most robust watermelon However, saltwater reduced waterleon vigor and there was minimal yield from this field due to Fall storms. ASD_bucket_Saltwater_summary ASD_field_Salwater study
ASD was successfully implemented at: (1) Ford Standing Farm in Brunson, SC. (2) Kindlewood Farms in Walterboro, SC (3) Rosebank Farms in Johns Island SC and (4) at Rollen Chalmers in Hardeville, SC. ASD was also attempted at Harleston Towles farm in Edisto Island SC. Flooding impacted that grower trial at Edisto Island.
High Tunnel Study ASD (Results)
Links Below contain the final results of objectives 1-4. On farm trials are also highlighted in the exit seminar given by Sohaib Chattha
The methods section includes results as well as the power points embeded within the methods section. The most comprehensive results are covered in the Exit Seminar for Sohaib Chattha (Exit seminar_Sohaib) as well as Josep Bazzle's exit seminar. seminar_bazzle_August
Education
Two graduate students conducted research in organic watermelon production in the state. One Master's student (Joseph Bazzle) worked on competition with watermelon and weeds in partial saltwater agricultural ecosystems. Another student's PhD (Sohain Chattha) work focused on the ASD component of the trial. Both successfully defended their thesis in July and graduate in August
Educational & Outreach Activities
Participation summary:
Graduate students Joseph Bazzle, Sohaib Chattha and myself have given research and extension presentations at field days, Southern SARE tours and at research conferences.
We have published 1 peer reviewed journal article, submitted 1 more and have 4 more in preparation.agronomy-15-00705-v2 (1)
We annually presented ASD at the Clemson watermelon field day and other fall field days https://news.clemson.edu/clemson-extension-announces-2025-peanut-cotton-vegetable-and-fruit-field-day/.
Research presentations were given on experiments related to the grant annually at meetings inclusive on Weed Science Society of America, Southern Weed Science Society and the American Society of Horticultural Scientists.
Typically we would present research from this grant at a Vegetable Field Day in June in Charleston, a watermelon field day at the Edisto Rec in July and a fall vegetable field day in September or October athe the Edisto Rec.
https://news.clemson.edu/clemson-leads-study-to-improve-organic-vegetable-production-using-carbon-waste/
Learning Outcomes
Standing Ford Farm in 2024 became the fist SC farm in close to a decade to grow USDA certified organic watermelon
Project Outcomes
Due to the interest in ASD and curiosity in exploring other carbon sources the Cutulle lab became a Co-PI on a USDA organic transitions grant focused on organic watermelon production using animal/agricultural waste products " Leveraging Concentrated Organic Biproduct Materials for Higher Nutrient Use Efficiency and Anaerobic Soil Disinfestation in Organic Vegetable Production" The data from this SARE project was used in the synthesis of the USDA-ORG grant.
LaTrobe University in Australia also became aware of our research and sought me (Dr. Cutulle) out to be adjunct professor and assist with a grant targeting ASD in watermelon in Australia.
As mentioned previously the biggest success from this grant was the prodcution of watermelon on an organic certifed farm in South Carolina (Angela Rainwater's), which had not been done in a decade or so. What made this more impressive is that it was done with a fall watermelon crop, which are tougher to grow when comapred to spring watermelons.
We were able to identify a carbon that worked well in South Carolina (Cotton seed meal).
Though the saltwater study provided negatvie results it does help provide a strategy to improve watermelon production in coastal area. (1) The lands that have been inundated with saltwater have to be remediated (brassica cover crop rotations) and (2) Stale seed techniques need to be implemented to control weeds in partial saltwater agroecosytems before planting a "salt tolerant crop". Weeds such as nutsedge simply have the competitive advanatge in salien conditions.
Project evaluator Cory Tanner (Lead of the Horticulture team) provided his evaluation below
Tanner_Project Evaluator Summary Next Steps in South Carolina_Southern_SARE
I think the biggest output with respect to collaborations is that we were able to work with farmers and successfully grow organic watermelon, which had not been done in the state in close to a decade. We also collaborated with the lead of Clemson Hort Extension (He was project evaluator). Extension agents were briefed on ASD at agent trainings, growers hosted on farm trials with our suggested ASD treatments, state department of agriculture official were present at many of the field days in addition to growers and extension agents.
Tanner_Project Evaluator Summary Next Steps in South Carolina_Southern_SARE
Cory Tanner, the project evaluator had some take home points from this study and what to do moving forward.