ASHS 2024 Conference

Identifying suitable genetics for low-input organic spinach production and ensuring an adequate supply of organic seeds are critical challenges for organic spinach breeders. This study comprehensively assessed 300 spinach accessions sourced from the USDA National Germplasm Repository and commercial checks. The field trials were conducted at Uvalde, TX, during the 2022-23 and 2023-24 growing seasons, focusing on biomass and nitrogen use efficiency. During the 2023-24 field trial, natural variations in leaf photosynthetic performance, including carbon assimilation, stomatal conductance, photosynthetic electron transport rate (ETR), and PSII actual photochemical quantum yield (PhiPS2), were analyzed utilizing an LI-6800 gas analyzer. The seed productivity traits, such as yield per plant and 100-seed weight, were evaluated at the Organic Seed Alliance Washington field site. The processed data were employed for Genome-Wide Association Analysis (GWAS) to identify underlying genetics associated with organic productivity and photosynthetic traits. Over 88k Single Nucleotide Polymorphisms (SNPs) dispersed across six chromosomes were utilized in the GWAS after stringent filtering criteria. Significantly associated SNPs and candidate genes were delineated for the targeted photosynthetic traits and seed productivity, shedding light on potential genetic factors influencing these crucial traits in organic spinach breeding programs.

Cover crops provide numerous ecological benefits to production systems. Maximizing these benefits requires identifying species and varieties that are the best fit both geographically and for the planting/termination time frame dictated by the accompanying cash crop system. In 2019, the University of Tennessee began a cover crop variety trial to help growers make better informed decisions on which of a broad range of cover crop species and varieties worked best in their specific region and production system. In fall 2022, in collaboration with the Southern Cover Crops Council, this trial was expanded to cover a 10-state region of the Southern US (TN, FL, NC, KY, VA, SC, TX, GA, AR, and AL) and became known as the Southern Cover Crop Variety Trial. This trial program is currently in its second year, with each trial year running from fall through the following spring. Trial sites were planted in mid-October each year. Cover crop cover, weed suppression, height, biomass, and estimated nitrogen release were measured in early and late spring. Twenty entries each were evaluated in the 22-23 and 23-24 trial years. However, as a fee-based program, entries were submitted by public and private institutions and varied from year to year. Eleven of the twenty entries were evaluated in both trial years. In year one, top-performers by rank were largely uniform across sites, consisting primarily of cereal rye and hairy vetch varieties. Many clover species, particularly crimson clover, exhibited greater variation in performance ranking among locations. Performance values varied significantly among and within locations, species, and evaluation period. Data collection for year two will be completed in Spring 2023 and will be presented.

When speaking to diversified vegetable crop growers, one of the most often cited challenges is the management of weeds. This issue is even more prevalent for organic growers who lack any effective chemical weed control method and rely on crews to mechanically remove weeds from the fields. One possible alternative is the use of terminated cover crops as mulch on the soil surface to act as a physical barrier to prevent weed emergence. This cover crop mulch can be advantageous for a grower in addition to cover crops improving soil health and providing a habitat for beneficial insects. This experiment compared vegetable beds with cover crops terminated with a roller crimper to bare soil beds on short (squash), intermediate (pepper), and long (eggplant) growing vegetable crops and assessed crop performance. In both 2023 and 2024 a cover crop mix of rye and field peas was successfully terminated and provided ample biomass on the soil surface at the time of vegetable transplanting and throughout their grower and harvest. We found that cover cropped treatments led to improvements in soil fertility, higher numbers of soil-dwelling beneficial insects, and lower weed pressure that led to significantly higher yields. These results demonstrate a potential system for organic growers to integrate into their operation as a practice that can reduce time and labor costs for weed management along with improving the soil fertility and creating a system requiring fewer inputs.

While organic production of specialty crops has been highly successful in southern California, it relies heavily on the use of plastic mulch and intensive tillage for weed management. A two-year study conducted from 2022 to 2023 aimed to evaluate the impact of plastic mulch and a cover crop based reduced tillage system using a -roller crimper to terminate cover crops on weed pressure and yield in organic strawberry production. Bare root strawberry crowns of the Albion variety were transplanted into four treatments: 1) Sorghum-sudangrass (S. bicolor x S. sudanense) seeded at 100 kg/ha (Sorghum 1), 2) Sorghum-sudangrass seeded at 200 kg/ha (Sorghum 2), 3) buckwheat seeded at 67 kg/ha, or 4) plastic mulch as standard practice. Cover crops were broadcasted on 1.5 m wide raised beds in May and terminated with a roller crimper in August. Both seeding rates of Sorghum-sudangrass effectively suppressed weed growth before and after termination compared to buckwheat. The significantly lower biomass of buckwheat after termination, relative to the Sorghum-sudangrass treatments, indicates variations in weed suppression efficacy among cover crops. Total differences in soil moisture, calculated based on data collected weekly from after cover crop termination to end of harvest, indicate that all treatments resulted in lower soil moisture levels compared to the plastic control, with the buckwheat treatment showing the most significant decrease. At harvest there were no significant differences between plastic mulch and Sorghum-sudangrass 1 and 2 treatments, indicating comparable yields. Buckwheat resulted in the lowest yield, experiencing a 50% reduction compared to plastic mulch. Based on the findings, plastic mulch and Sorghum-sudangrass planted at different seeding rates can be considered effective alternatives for weed suppression and maintaining yields comparable to conventional plastic mulching. The choice between Sorghum-sudangrass seeding rates may depend on factors such as cost, availability, and specific field conditions. The reduced biomass production of buckwheat compared to Sorghum-sudangrass, coupled with its rapid decomposition rate, resulted in diminished efficacy of buckwheat in weed suppression. Consequently, reduced weed control was observed, leading to significantly lower yields in buckwheat-treated plots compared to Sorghum-sudangrass and control treatments. These findings suggest that buckwheat may not be a viable option for organic strawberry production under comparable conditions, emphasizing the importance of selecting cover crops with longer-lasting weed-suppressive qualities.

Hemp (Cannabis sativa L.) is a highly versatile crop that has attracted considerable attention among farmers due to its diverse applications. Recent studies have sought to establish a fundamental understanding and baseline of the nutritional requirements of hemp, opening up possibilities for organic hemp production. Our research focuses specifically on evaluating the productivity of a floral hemp variety using different regenerative practices, with a particular emphasis on organic soil amendments that promote soil health in Piedmont area of North Carolina. The field experiment was conducted at North Carolina A

The evolving effects of climate change and intensive agricultural practices have adversely affected soil health and crop yields. This necessitates the need to maintain and improve soil health for sustainable food production. Biochar, a carbon-rich material produced from pyrolysis of biomass is being considered as a novel soil amendment that can potentially restore soil health and improve crop yields. Several studies have reported both positive and negative effects of biochar on crop yields while focusing mainly on one type of biochar and a single plant cultivar. However, the effects of different types of biochar and its interaction with plants with different genetic backgrounds has remained unexplored. In this study, we evaluated the impact of six different biochars on the growth performance and fruit quality of three tomato (Solanum lycopersicum) cultivars. The hypotheses that (1) biochars derived from different feedstock sources would produce unique phenotypes in a single cultivar of tomato, and (2) single feedstock-derived biochar would produce different phenotypes in each of the three tomato cultivars were supported by obtained results. This study demonstrated that plant genetic background and biomass source are important variables to consider for using biochar as a soil amendment.

Strawberries are typically grown in high tunnels in the Intermountain West region to protect the flowers and buds from early and late-season frosts and extend the growing season. Organic farmers rely on N mineralization from organic sources to supply plant-available N which can be inadequate for plant needs, especially when temperatures are low. To support cultivar selection for organic strawberry production in high tunnels, greenhouse cultivar trials were conducted to determine if some strawberries grow better on compost than others. Plants were grown for six weeks in a mixture of turface and peat moss with and without compost. A complete liquid fertilizer with and without added N was supplied daily. Leaf, crown, and root dry weights, tissue, and compost N at the beginning and end of each trial were measured and leachate was collected daily and analyzed for nitrate and ammonium. Plant chlorophyll was determined at the end of the experiment. Plants that received liquid N fertilizer grew more, absorbed more N, and had a higher chlorophyll reading compared to plants that received the compost and N-free fertilizer treatment. Ammonium was leached out of the compost-treated pots in the first two weeks while little nitrate was lost. Some cultivars performed better than others on the compost treatment. This suggests that some strawberry cultivars are better able to grow on organic nitrogen sources than others but, additional N fertilization may be needed.

Brassica crops are susceptible to a variety of insect pests of particular significance in organic production systems, including flea beetles, aphids, and lepidopteran caterpillar pests. These pests are abundant on brassicaceous vegetable crops throughout the U.S. and populations frequently are high enough to significantly reduce crop quality. There is an increased interest among small and mid-size vegetable growers to adopt poly-covered tunnels to protect high value horticultural crops. Tunnel production allows for season extension, can protect crops from adverse weather conditions, improve the quality of horticultural crops, and may also influence plant-insect dynamics. Photoselective poly coverings influence light wavelength and transmission in tunnel environments and may affect plant physiological responses as well as incidence of disease and herbivory by insect pests. Here, we explored the impact of UV light blocking and UV light transmitting poly coverings on Lacinato kale (Brassica oleracea var. acephala) production and the effects on pest and beneficial insect populations in a tunnel environment compared to an open field system on certified organic land in Morris, MN. Our results showed that total kale harvestable yield was similar between the poly covered tunnels and open field plot treatments. No differences in yield or insect pest pressure were observed between UV light blocking or transmitting poly covered tunnels but were observed between tunnels and the open field environment. Imported cabbageworm populations were 75% higher in tunnels versus open field plots (P=.0023), however the inverse was observed for cabbage loopers, which were 60% higher in open field plots (P=.0072). No flea beetles were found in tunnels, and an average of 1 beetle/plant was observed in open field plots. Diamond back moth and aphid populations were not different between the tunnel and the open field plots. Overall, insect pest populations did not reach economically damaging thresholds during the study period, likely due to the field plot location which did not have a history of brassica production. Our results showed that light transmission and ambient air temperatures were similar under the photoselective poly coverings. We observed that pest pressure increases rapidly in tunnel environments as the season progressed regardless of poly covering. Although our study did not observe differences in the yield or quality of kale across production systems, there were differences in insect pest populations across systems, indicating a different management approach may be needed to prevent crop damage in tunnel environments.

Anaerobic soil disinfestation (ASD) is a promising organic pest management strategy and is an alternative to chemical-led approaches that has shown potential to manage weeds and soil-borne pathogens in organic vegetable production systems. ASD is facilitated by incorporating carbon sources into the soil, tarping the soil with plastic mulch, and irrigating to the soil saturation point. To evaluate the impact of ASD on weed and nematode management in organic-grown sweetpotato, greenhouse studies were conducted at Clemson University, Clemson, South Carolina. Experiments were laid out in a randomized complete block design in 2-gallon microcosms with two carbon sources [ASD (soil amended with chicken manure molasses as carbon source) and non-ASD (non-amended control)] in the main plot and twenty sweetpotato genotypes in subplots. Three-week-old seedlings of tomato (cv. Rutgers) were planted in each microcosm followed by inoculation with 10,000 eggs of the southern root-knot nematode (Meloidogyne incognita). ASD was initiated one month post inoculation to allow nematodes to complete one life cycle. At the time of the ASD initiation, each microcosm was also inoculated with weed seeds [yellow nutsedge (10 tubers) and carpet weed (100 seeds)]. ASD was conducted for three weeks, followed by the transplantation of sweetpotato slips after one week of ASD termination. Weed counts, abundance of nematode second stage juveniles (J2) in soil, and sweetpotato above ground biomass data were collected. Our results suggested that the microcosms receiving the carbon amendment spent the most time under anaerobic conditions (

Entomopathogenic fungi offer an alternative strategy for citrus growers seeking environmentally friendly pest management solutions. This study aimed to assess the ability of a commercial strain of the fungus Beauveria bassiana to become endophytic in citrus plants after a single foliar application. A completely randomized block design, consisting of ‘Valencia’ sweet orange trees (Citrus × sinensis) grafted on ‘US-942’ (Citrus reticulata × Poncirus trifoliata) rootstock, was established under greenhouse conditions. Treatments comprised 6 replications of treated plants in two separate greenhouses (n = 16 per greenhouse), along with one control (water only). Treated plants were foliar sprayed asynchronously with the fungus at the beginning of each experimental trial per treatment. To assess endophytism over time, a series of cohorts were destructively sampled every two months. Spore deposition was assessed using cover slips post-spray application of all treatments. Additionally, detached leaves collected post-spray were imprinted on potato dextrose agar (PDA), amended with dodine and bactericides, to determine spore coverage of the leaf surface by counting colony forming units. To assess endophytism, sterile samples of plant organs (i.e., leaves, stems, and roots) were placed onto PDA-dodine plates to allow detection of phenotypic mycelia. Results from the first cohorts indicated successful application of the fungi on the citrus leaves, and endophytism was assessed after two months. Additionally, no statistically significant changes were recorded in terms of plant height, root, stem, and leaf biomass, as well as stem girth. This project contributed to a clearer understanding of the long-term endophytic persistence of commercially available entomopathogenic fungi and their effect on plant growth in citrus trees. The trial will continue in the field for additional screening.