Recipient Organization
CLEMSON UNIVERSITY
(N/A)
CLEMSON,SC 29634
Performing Department
(N/A)
Non Technical Summary
Weed and nematode infestation significantly reduces yield in sweetpotato. Minimal economically relevant options are available for use in organic sweetpotato to control weeds and nematodes. The research proposed here focuses onevaluating Anaerobic Soil Disinfestation (ASD) in sweetpotato field trials for crop tolerance and weed and nematode management. ASD is biological fumigation process that utilizes carbon inputs and sealed soil to produce volatile organic compounds that kill soilborne pests. In addition to ASD, we will evaluate the impact of novel UV reactive mulch on controlling weeds and total sweetpotato yield. Finally, we will integrate ASD and UV reactive mulch with Sweetpotato germplasm that have increased tolerance to weeds and/or nematodes. Specifically, we will look at germplasm that exhibits a bunch type growth habit and resistance to root knot nematode species. Economic analysis will be conducted to determine how profitable these treatments will be compared to grower standard practices These experiments willbe conducted at the Clemson vegetable research facility in Charleston, the Edisto Research and Education Center in Blackville, SC and at grower locations along Coastal SC.
Animal Health Component
55%
Research Effort Categories
Basic
15%
Applied
55%
Developmental
30%
Goals / Objectives
Our long-term goal is to develop an integrated management approach in organic sweetpotato production that combines anaerobic soil disinfestation (ASD), novel plastic mulch, and sweetpotato clones with improved resistance to the southern root-knot nematode (SRKN) and weed infestation. Our integrated research, extension, and outreach activities will lead to effective management strategies to increase domestic organic sweetpotato production.Evaluate ASD on sweetpotato germplasmScreen a panel of 20 sweetpotato clones to an ASD environment. Include PlantIntroductions (PIs) and commercial germplasm that have either a bunched type growth habit or resistance to southern root-knot nematode (SRKN) as well as commercial standards.Evaluate the impact of time of transplanting (0, 1, 2, and 3 weeks) after ASD has been terminated with selected clones from objective 1a.Evaluate ASD with different locally sourced carbon sources for the ability to reduce the incidence and population density of SRKN and weeds in sweetpotato fields.Evaluate the impact of novel plasticulture materials to control weeds and grow sweetpotato in the field.Integrate thebest practices of ASD, plasticulture material, and improved sweetpotato lines todetermine impact on weed infestation and nematode suppression.Evaluate combination of plasticulture, sweetpotato germplasm, and ASD at Coastal Research andEducation Center (CREC)/United States Vegetable Lab (USVL) and on farm locations.Evaluate the impact of ASD on soil microbial dynamics in sweetpotato production systems.Conduct a cost-return analysis of ASD in combination with improved plastic mulch and novel sweetpotato germplasm compared to currently used management practices and sweetpotato cultivars.Communicate results and guidelines to stakeholders, scientists, and industry professionals in the Southeast and other regions in the U.S. through an aggressive extension and outreach program.
Project Methods
Objective 1a: Screen a panel of 20 sweetpotato germplasm to an ASD environment. Include PIs and germplasm that have either a bunched type growth habit or resistance to SRKN as well as commercial standards.Objective 1b: Evaluate the impact of time of transplanting 0, 1, and 2 weeks after ASD has been terminated with selected cultivars from objective 1a.Methodology and Data Analysis: For Objective 1a, initial greenhouse trials will be conducted at the CREC/USVL. The experiment will be structured as a randomized complete block design with five replications. The treatments will consist of a factorial of carbon source (cottonseed meal) by 20 sweetpotato PIs and commercial cultivars that include several bunched type growth habit and/or resistance to SRKN as well as commercial standard cultivars such as Beauregard and Covington. The experimental unit will consist of a 5-gallon bucket microcosm filled with native South Carolina soil. For nematode experiment, the soil will be sterilized followed by inoculation of 10,000 eggs of SRKN. Amendments will be added to the buckets at a rate equivalent to seven tons per acre, and half the buckets will be covered with an impermeable film (Tiff) mulch, the units that will undergo ASD. An initial irrigation of 5 cm of water will be applied. Water will be applied based on moisture and redux potential measurements throughout the trial. ASD treatment will be performed for 6 weeks, then plastic will be removed. Percent weed emergence and weed biomass will be recorded 6 weeks after ASD initiation. Nematodes will be extracted from a 100 cm3 subsample using centrifugal-flotation technique (Jenkins, 1964). Nematode enumeration will be conducted enumerated using a dissecting microscope at 40x magnification. Sweetpotato biomass will be harvested at 12 weeks after transplanting. All data will be subjected to analysis of variance using JMP. Means will be separated according to Tukey's (α= 0.05). Contrast statements will be constructed to analyze differences between specific ASD-carbon source-genotype treatments. For Objective 1b, experiments will be conducted as a randomized complete block with four replications. The treatments will be structured as a factorial with three transplant timings, two carbon amendment treatments, and four sweetpotato cultivars. Sweetpotato biomass will be harvested 12 weeks after transplanting.Fields selected for trials have been previously inoculated with SRKN (M. incognita) and have been planted with susceptible host crops in successive years to increase and maintain the nematode populations in the soil. Nematode populations within each ASD treatment block will be assessed at four times during each growing season (Before ASD treatment, planting, mid-season, and final harvest). Replicate soil samples will be taken from each plot during each time point. For each sampling, twenty soil cores will be taken in a zig-zag pattern across the length of each row within the crop root zone (when present) using a 12-inch soil probe. Soil cores will be combined in a clean bucket, and thoroughly mixed to provide a uniform 500 cm3 sample that will be delivered to the Nematode Assay Lab at Clemson University for nematode extraction and counting. Mean counts of RKN juveniles per 100 cm3 of soil within each plot will be generated and used to assess the effect of ASD treatments.The experiment will be conducted as a randomized complete block split-plot design with four replications at locations (Charleston and Edisto REC, Blackville, SC). The treatments will be constructed as a factorial with the main plot factor being carbon source amendment (Chicken Manure + Molasses, cotton seed meal, brassica waste, mixed cover crop material, brewers' yeast, or no carbon amendment). All relevant chemical analyses (particularly, C:N ratio) of the carbon sources will be done. To prepare raised beds, the field will be mechanically disked to breakdown weeds, improve soil granulation, and surface uniformity. Raised beds will be prepared using tractor-mounted bed former. Soil carbon treatments will be added to the plots manually and mixed with tractor-mounted peanut hoe. Then, a tractor mounted plastic bedder and drip tape implement will be used to re-bed the field and cover with plastic mulch. Assigned plots will be covered and completely sealed with an impermeable film (TIF) black polyfilm mulch (1.25 mil). An initial 5 cm irrigation will be applied to facilitate Anaerobic Soil Disinfestation in the soil. ASD performed for six weeks. Oxidation-reduction potential (ORP) sensors (Pt combination electrodes, Ag/AgCl reference; Sensorex, Garden Grove, CA, USA) will be installed in the center of all plots at a 15-cm depth to monitor anaerobic soil conditions. A data logging system (CR-1000X with AM 16/32 multiplexers, Campbell Scientific, Logan, UT, USA) will be used to record the outputs from the sensors which monitor readings every 30 s and are averaged on an hourly basis. Nematode counts, weed counts, and sweetpotato yield (weights as well as sorted graded counts) will be taken at the end of the study. All data will be subjected to analysis of variance using JMP. Means will be separated according to Tukey's (α= 0.05). If appropriate, data will be averaged across years. A Shapiro-Wilk diagnostic will be used to assess normality on multiple dependent variables.Evaluate the impact of novel plasticulture materials to control weeds in sweetpotato fields.Methodology and Data Analysis:The experiment will be conducted as a randomized complete block split plot with four replications. The treatments will be constructed as a factorial with main plot consisting of a plastic mulch treatment (black UV reactive plastic, white UV reactive plastic, black TIF plastic, white TIF plastic, and bare ground). Each main plot treatment will be split into sweetpotato cultivar (Beauregard, Covington, and two bunched type cultivars). Beds will be formed in the same manner as was described in Objective 2. Each main plot will be 60 ft in length while each subplot will be 15 ft in length. Weed species counts will be collected throughout the trial and sweetpotato yield will be collected at the end of the study. The experiment will be repeated in time as well as space (Charleston SC and Blackville SC). PD Cutulle will coordinate purchasing of novel plastic materials and conduct the trial in Charleston while Co-PI Ward in collaboration with project evaluator Miller will implement the trial in Blackville, SC. Similar statistical methodology will be used as was described in Objective 1 and 2.Partial budget analysis and change in production profits: Partial budget analysis is a widely used analytical method by the farm owners and managers to estimate the net economic effects of changes in production systems. It allows business managers to evaluate changes in production profit - not profitability. It is a standard method to compare the financial impacts of changes in various production practices, such as weed management (Meagher et al. 2021), soil anaerobic disinfestation (Donahoo et al. 2021), and planting methods (Mihretie et al. 2021). This analysis will only consider partial factors that would change because of the adoption of alternative practices, since the remaining elements that will not change will not have any impact on profits. Therefore, the analysis would reveal how profits would increase or decrease with the adoption of alternative farming practices. Labor, cost, and time savings will also be included in the partial analysis, as appropriate.