ONION-IQ (IMPROVE QUALITY): IMPROVING QUALITY, RESILIENCE, SOIL HEALTH AND FOOD SAFETY IN ORGANIC ONION IN THE SOUTHEASTERN AND SOUTHWESTERN U.S.

<b>Project Methods</b><br> Objective 1. Evaluate cultural practices that reduce soil-borne bacterial pathogens and weeds (digital scouting for weeds and diseases) and increase/sustain growth of beneficial microflora, and predators and natural enemies (20% effort).(i) Assessing robustness of a qPCR assay that differentiate onion-disease-associated vs. saprophytic Burkholderia spp.in soil:(ii) Evaluate cultural practices. We propose to monitor the effects of cultural practices in separate field trials in GA and TX (solarization duration treatments and biofumigant-crop treatments) on the populations of onion-disease-associated Burkholderia spp. in soil. (ii a) Soil-solarization: We will work with organic onion producers from GA and TX to assess if soil solarization can effectively reduce populations of onion-disease-associated Burkholderia spp. in soil. A total of four field trials in organic certified fields (two in each state) over a period of two years (Y1 and Y2) in GA and TX will be conducted.Experimental design: We will evaluate the effectiveness of a 60-day duration of solarization in reducing both bacterial pathogens in soil, thereby reducing sour skin and slippery skin incidence/severity in onion bulbs (pre- and post-harvest).(ii b) Biofumigation: We will assess if biofumigation with two known biofumigant Brassica species, namely Sinapis alba (white mustard) and Brassica juncea (brown mustard) can effectively reduce B. cepacia and B. gladioli pv. alliicola in soil.Experimental design: We will evaluate three cultivars that will include a cultivar each from B. juncea (cv. Kodiak) and S. alba (cv. Ida Gold) and a blend of S.albaandB. juncea (cv. Caliente 199) for their biofumigation abilities to reduce both bacterial pathogens in soil compared with a no treatment control plot and thereby reducing sour skin and slippery skin incidence/severity in onion bulbs (pre- and post-harvest). Hence, we will utilize a randomized complete block design with four replicates/plots. Each field trial will consist of plots with dimension (50 ft × 6 ft) with 6 ft to 10 ft borders on all sides. Each brassica cover crop for biofumigation purposes will be grown and maintained according to the UGA and TAMU Cooperative Extension Recommendations. At flower initiation, these crops will be flail mowed and immediately rototilled in the soil. Prior to mowing, brief over-head irrigation will be employed. Immediately after incorporation, a transparent 30µM-thick, low density polyethylene mulch will be laid in strips using a tractor.Objective 2: We will focus on evaluating and optimizing N-fertilization programs in organic onion that increase productivity, improve soil health, and improve food safety (20% effort). Evaluation of two organic fertilizer sources (PL, and COF) and assessment of cool season N-release patterns.Field sites: There will be four organic certified field sites two will be in GA: Tifton, Athens and two will be in TX (TAMU): Overton, College Station. The project will conduct studies over two consecutive years (Y1 and Y2), providing a total of 4 sites for each year under varied conditions of climate and soil in the southeastern and southwestern US. The field study will evaluate N release from two organic fertilizer sources (PL, and COF) as a function of temporal application patterns. The PL will be locally available broiler litter and the COF will be a Nature Safe 10-2-8.factorial design and 4 replications of each combination plus a non-amended control (36 plots total) (Right). Plots will be 20-ft long (on-raised beds), containing 4 rows each of onions, separated by 10-ft alleys for adjacent plots within the same row.(i) Nutrient assessments: Preplant and at-harvest samples will be collected for routine and micronutrient soil tests for all 4 sites each year (2 TX and 2 GA). Soil samples will be collected at the 0-15 cm and 15-30 cm depths by hand sample probe. Routine soil analyses will be conducted on all samples as well as, SOM (loss on ignition) total C and N (combustion), active C as PMO×C (49), NO3-N and NH4-N (50). Organic fertilizers will be analyzed for total nutrient content (acid digestion and ICP-AES), total C and N, NO3-N and NH4-N soluble carbohydrates, cellulose/hemicellulose, and lignin to provide supporting data for prediction of N mineralization.Influence of organic N-fertilizer sources on food safety; Salmonella Newport survival in soils. BSL2 level-growth -chamber assessment: Food safety aspect in this proposal will be conducted only in GA under controlled BSL2 facility at the Center for Food Safety, UGA, Griffin. This aspect will be led by Co-PIs Dunn and Kumar. The survival of Salmonella enterica serovar Newport (onion outbreak isolate) will be evaluated in soil obtained from organic onion cultivation fields. The soil (100g portions) will be seeded with Salmonella Newport (approx. 2 and 5 log CFU/g). Soil will be amended with raw and treated amendments of poultry origin (used by organic growers). Traceability of the Salmonella strains will be facilitated by developing resistance to ampicillin and streptomycin (100 µg/ml) as described earlier (53). Survival will be evaluated over a duration of 120 days (10-day intervals) using culture-based enumeration on selective media and enrichment-based presence/or absence tests to assess if population declined below the limit of detection. Non-amended soils will be used as a comparative control. Objective 3: Integration of organic production practices (organic N sources, biofumigation, and solarization) on onion-disease-associated Burkholderia spp., crop quality, food safety, nutrient cycling, and the soil microbiome (30% effort).Experimental design: In Y3 and Y4, integrated field trials will be conducted, one in each of the two locations (GA and TX). Three main treatments will be used: biofumigation, solarization, and non-treated control. Within each main treatment, four fertility sub-treatments will be applied: F1). poultry litter (PL) applied at the beginning of the disease-reducing techniques (at planting of mustard for biofumigation, at tarping for the solarization, and to the soil in the non-treated control); F2). PL applied at onion planting, F3) commercial organic fertilizer (COF; Nature Safe 10-2-8 organic mix) applied at onion planting; and F4). non-fertilized control. PL and COF will be applied at a rate equivalent to 200 lbs N/acre.Objective 4: Analyze the economic feasibility of the proposed integrated production approaches for organic onion in Southern U.S. (10% effort) (Greg Colson; Economist).In Y1, a survey will evaluate economic losses due to sour skin and slippery skin in organic onion growers and packers across the southeastern and southwestern U.S. The survey will also gather information on management, variety selection, fertility and irrigation regimes, and organic pest and disease programs in their region. Project team members and stakeholder advisory panel (SAP) will analyze the results. Economic analysis will be calculated annually (Y1 and Y2 assessments of individual components, and Y3 and Y4 assessments of integrated components).Objective 5: Extension, outreach and education (20%): We will extend our information at local and regional meetings focusing on organic onion production, and disease management after the first year of trials in GA and TX. Based on our experience with Extension and outreach (seven Extension specialists on the team, including PD and several Co-PIs), we are confident of identifying numerous opportunities to present information in a face-to-face format and also reach a large contingent of vegetable growers. The event that will capture a large cohort of vegetable growers is the SE Regional Fruit and Vegetable Conference (annually in Savannah, GA) and the GA Organics Conference (annually in Georgia).