ASHS 2024 Conference

Climate change and global warming are increasing the frequency of drought incidents, which negatively impact crop production. Onion is one of the major vegetable crops produced in Texas, which requires a long growth period and prone to drought stress as it has shallow roots and needs frequent irrigation. Plant biostimulants may offer a potential solution to mitigate drought stress in onion production. This study investigated the effect of different biostimulants (no application as control, Kelpak, Spectrum DS, MycoApply, and Tribus Continuum) on onion seedling growth under well-watered and drought stressed (50-60% field capacity) conditions. Results showed that there was no significant interaction between biostimulants and drought stress on most of the parameters we collected. All biostimulants significantly increased shoot weight, leaf area, plant height, and root weight compared to the control. Notably, Spectrum DS, MycoApply, and Kelpak specifically enhanced root morphology by increasing root length, root area, and root volume compared to the control. But the application of biostimulants didn’t significantly affect average root diameter or the number of root tips. Drought stress significantly reduced the growth of onion seedlings across all measured parameters, except for the number of root tips, compared to the well-watered group. While drought stress caused a 36.9% decrease in shoot fresh weight, application of Kelpak, Spectrum DS, MycoApply, and Tribus Continuum increased shoot fresh weight by 29.8 to 34.9%, partly offsetting the growth reduction and alleviating the stress experienced by the seedlings. In conclusion, the application of the investigated biostimulants shows promise for enhancing drought tolerance in onion seedlings.

Food and farm waste processed by anaerobic digestion (AD) generates a nutrient-rich digestate suitable for use as a biofertilizer. Small-scale AD systems production of biofertilizer offer an on-site solution accessible to individual households and small horticultural producers. Unlike common and more complex AD solutions, small-scale systems do not require extensive management or infrastructure investments. In 2022, we investigated the nutrient content and usability of digestate from two small-scale biodigester models: A commercially built digester with a 1,200 L digester tank, and a prototype we designed with a 114 L capacity. Locally sourced fresh raw cow milk served as inoculum. Over a span of 16 weeks, 12 randomly selected households in Bozeman, Montana, tested the two digester models, feeding them with the food waste they generated. Six of the households received the commercial model, and six tested the prototype. Digestate samples were collected biweekly to analyze their chemical properties and potential as a biofertilizer. After 16 weeks, we blended all digestate, taking equal parts from all household samples, and tested it in a greenhouse study as a fertilizer for red cabbage (Brassica oleracea L. Capitata Group) seedlings. In addition to a control treatment where no biofertilizer was used, we applied 40 ml of biofertilizer per plant in a “high dose treatment” and 20 ml biofertilizer per plant in a “low dose treatment.” Each treatment involved 50 cabbage plants growing individually in trays of 10 cm diameter. On a weekly interval, the biofertilizer was sprayed on the substrate, with amounts varying by treatment. The substrate consisted of loam soil, washed sand, Canadian sphagnum peat moss, perlite, vermiculite, and dolomitic lime. Seedlings were irrigated manually every second day. To ensure sufficient nitrogen supply, all three treatments received an initial application of 40 mL of fish emulsion per cabbage plant. No pest or disease management practices were implemented. After 30 days, all plants were harvested, and their aboveground dry biomass was measured. A trend towards higher aboveground dry biomass in the "high biofertilizer dose" treatment compared to the "low biofertilizer dose" and control treatments was observed. Additionally, the aboveground biomass underwent nutrient content analysis, revealing a tendency towards the highest potassium content in the "high dose treatment." This study showed that household food waste processed through small-scale AD systems generates valuable biofertilizer that can help manage crops’ nutrient needs.

The growth of the U.S. organic vegetable industry is currently limited by the availability of viable and effective solutions for the management of soilborne pests and pathogens. Anaerobic soil disinfestation (ASD) is a pre-planting biological method proposed for the management of a range of soilborne pests and pathogens affecting horticultural crops. As an organic amendment-based approach, ASD is implemented incorporating in the soil an easily degradable carbon (C) source, tarping the soil with plastic mulch, and irrigating the soil to field capacity. The selection of organic amendments suitable as C sources is critical for the efficacy of the treatment and its sustainability. Understanding how the physicochemical properties of alternative amendments may affect the efficacy of the ASD treatment, the soil fertility during and post ASD, and consequently the crop performance is critical. Therefore, a study was conducted on organic-certified land at the Penn State High Tunnel Facility to compare wheat middlings (WM), molasses (M), and soybean meal (SM) and their combination as C sources. Treatments tested included WM, M, SM, WM SM, and M SM applied at the standard rate of 6 Mg/ha of total C, SM0.5 applied to reach the equivalent of 3 Mg/ha of total C, and the untreated controls with (UTC W) and without (UTC) initial irrigation. Three weeks after the ASD treatment, Romaine lettuce was planted as a test crop. Organic amendments tested as C source were characterized by different C:N ratio, ranging between 6.3 (SM) and 57.2 (M). All the amendments tested ensured the achievement of good soil anaerobicity levels. The C:N ratio of the amendments significantly influenced the availability of nitrate-N during and post-ASD, thereby influencing the lettuce crop yield and quality performance. Having the highest C:N ratio, M applied by itself decreased the availability of nitrate-N during and post-ASD. Instead, SM characterized by the lowest C:N ratio, increased the availability of nitrate-N. The availability of N during the growing cycle, determined by the characteristics of the organic amendment and by the ASD treatment influenced the crop yield and nutritional profile. The results of the present study provide new insight for the selection of alternative C sources and the optimization of the ASD treatment in organic protected culture systems.

The utilization of cover crops in vineyards has been promoted for their role in moderating soil climate, thus enhancing vineyard resilience to extreme weather conditions. This study evaluated the effectiveness of three drive-row cover crop treatments in regulating soil moisture and temperature within an irrigated organic vineyard characterized by loamy sand soil, located in the semiarid Okanagan Valley, Canada, over the period from 2021 to 2023. Selection of cover crop species was informed by prior greenhouse and field screening experiments. The implemented treatments, established in May 2021, included a mixture of perennial ryegrass, tillage radish, and white clover (PRTRWC); a fescue mixture with white clover (FWC); cereal rye with hairy vetch (CRHV); and a Control (existing vegetation/weeds). The vineyard was equipped with drip lines and undercanopy sprinklers. Soil moisture and temperature were monitored every four hours using Teros 11 sensors at a 10 cm depth in the drive-row. Seasonal observations revealed the highest soil volumetric water content (Ɵv) from November to April, aligning with cooler temperatures and increased precipitation. The Ɵv ranged from 0.10 to 0.14 and significant differences in average Ɵv were noted among the all treatments over the three growing seasons (May to Oct), with CRHV displaying the highest levels, followed by FWC, Control, and PRTRWC. Notably, substantial differences in Ɵv (

The plant rhizosphere plays a key role in plant function and immunity. Apple Replant Disease (ARD) is a dysbiosis in apple rhizosphere environments that have a history of apple cultivation. Due to increased intensification of apple growing systems and land scarcity, ARD incidence is on the rise and can result in a 50% loss of profitability to growers. Soil fumigation is a common practice for mitigating ARD, but has limited efficacy and is not allowed in some areas because of potential for environmental damage and human harm. Using resistant rootstocks is a key strategy in overcoming ARD. To understand rootstock resistance, it is important to describe and characterize the microbial communities of various rootstocks in an environment conducive to microbial health. We planted an organically managed apple orchard with 5 randomized repetitions of 15 different rootstocks. In both 2022 and 2023, we sampled the soil adhering to the roots of these trees for DNA extraction in order to characterize both bacterial and fungal microorganisms in the rhizosphere of the rootstocks in our research. We also established an aeroponic greenhouse trial (randomized with three repetitions) to sample rhizodeposits from 6 of the rootstocks used in the orchard trial, with the aim of characterizing metabolites with untargeted HPLC/LCMS. Bacterial phyla and genera differed in relative abundance between the rootstocks. A sparse PLS (partial least squares) discriminant analysis of rootstock exudates revealed differential sorting of some rootstocks. Neither study revealed clear biological indicators for ARD resistance, but the results evince that rootstock genotype does influence both microbial community and tree root exudation patterns.

Consumer demand for organic and locally sourced plant-based protein has created an opportunity for farmers in the Northeast and Upper Midwest who are interested in organic dry bean (Phaseolus vulgaris) production. However, standard practices for organic dry bean production can degrade soil health because of the soil tillage and cultivation used for weed management and harvesting. Such soil disturbance is not only labor and fuel intensive, but it also makes soil vulnerable to extreme weather, which is a major concern given the increased frequency of heavy rain events. Building on success with no-till planting soybean into mechanically terminated cereal rye, a team of researchers and stakeholders from Wisconsin, New York, Maine, and Vermont developed a project to assess dry beans for cover crop-based, organic no-till production. In addition to crop yield and profitability, field experiments focused on assessing weed and disease management. Findings from several experiments show that dry beans can successfully emerge through mulch from cover crops and produce yields that are comparable to standard tillage based organic production. In an experiment conducted at two sites in 2020-2021 and 2021-2022, a cover crop mixture of hairy vetch and cereal rye produced relatively high biomass (>7000 kg/ha), which suppressed weeds (< 500 kg/ha) and resulted in relatively high (2500 kg/ha) organic black bean (cv. ‘Zorro’) yield. Results are congruent with previous research showing that mulch from cover crops can suppress weeds, particularly small seeded annual weeds. In an experiment conducted in 2016-2017 and 2017-2018, we showed that mulch from mechanically terminated cereal rye (Secale cereale) can also reduce the incidence of the fungal disease white mold (Sclerotinia sclerotiorum) in organic no-till planted dry bean. Although mulch from cover crops can suppress weeds and soil borne diseases, achieving the high cover crop biomass production that is necessary for suppression can be challenging. A field experiment was conducted in Wisconsin, New York, Vermont, and Maine in 2022-2023 to test the efficacy of interrow mowing weeds that break through the mulch in the space between crop rows. Preliminary results show that interrow mowing has potential to reduce yield loss from weeds and weed seed production in organic no-till planted dry bean production. Additional research is needed to develop management guidelines for no-till planting organic dry beans into rolled-crimped cover crops.