ASHS 2024 Conference

Standard organic farming production practices for specialty crops frequently involve the use of polyethylene plastic mulch or mechanical soil disturbance to reduce weed competition and enhance crop yields. Although successful, these practices come with environmental consequences, including soil pollution and loss of soil organic matter. As such, alternative methods that prioritize the long-term health of the soil and minimize environmental impact are needed. We performed a field experiment to assess and compare the influence of five soil management systems on soil characteristics, weed pressure and yield in globe artichokes production. Artichoke (Cynara scolymus L.) seedling cvs. Tavor were established on raised beds as: A) intercropped with white clover (Trifolium repens L.) as living mulch, or B) intercropped with crimson clover (Trifolium incarnatum L.) as living mulch, or C) transplanted into mixture of buckwheat (Fagopyrum esculentum M.) and pea (Pisum sativum L.) cover crop residue or D) intercropped with Kurapia (Lippia Nodifera L.) as living mulch, or E) transplanted in PE plastic mulch. Results show that white clover increased soil organic matter (SOM), soil potassium and manganese content, water extractable carbon, soil respiration (CO2), soil nitrate, ammonium and total soil nitrogen compared to plastic mulch at 360 DAS (Days After Seeding). White clover weed suppression ability did not differ from crimson clover and buckwheat/pea mixture. Crimson clover increased SOM at preharvest sampling. Both clovers decreased artichokes yield per plant when compared to plastic mulch. Kurapia increased soil sodium content compared to plastic. Cover crop/reduce tillage system increased SOM at 120 DAS compared to plastic. Due to biomass decomposition, the suppression ability of this mixture decreased over time. Plastic mulch increased copper and iron soil concentration. Artichoke yield from plants grown on plastic mulch had comparable bud weight and yield to buckwheat/pea mixture and Kurapia. The potential to enhance soil nitrogen and carbon levels over a longer period of white clover makes it a valuable choice in systems aiming to improve soil fertility. Crimson clover emerges as the most promising among the clovers, exhibiting less competition compared to white clover, effective weed control, and, although the yield is lower than that achieved with plastic mulch, it maintains a well-balanced crop load. The reduced tillage system has shown promising results, successfully managing weeds adequately and allowing for a satisfactory level of production. No detrimental impact on yield were found intercropping artichokes with Kurapia and, but its effect on soil health was limited.

In the Southeast United States, control of parasitic nematodes in vegetable growing systems has traditionally relied on soil fumigation before planting vegetables. However, new regulations on the application of fumigant pesticides and concerns about their toxicity to non-target organisms are compelling growers to adopt sustainable alternatives. This study examined the effects of winter cover crops and subsequent production of cabbage treated with a non-fumigant nematicide on root-knot (Meloiodgyne incognita) and stubby-root (Nanidorus minor) nematodes. Off-season treatments consisted of oilseed radish cvs. “Control” and “Image”, cereal rye cv. “Wrerens Abrussi”, oat cv. “Tachiibuki”, black oat cv. “Protex” and mustard cv. “Caliente”. In-season treatments consisted of an untreated check and the nematicide fluensulfone, applied through the drip irrigation system one week before transplanting cabbage into raised beds covered with plastic mulch. A weedy fallow treatment was also included for comparison. After growing cover crops and incorporating plant residues into the soil, M. incognita population density was significantly reduced only in plots where Tachiibuki oat was grown. None of the cover crops reduced the population density of N. minor. Nematicide application on cabbage significantly reduced M. incognita populations in plots previously grown with Tachiibuki and Pratex oats, and mustard compared to the untreated check. Similarly, the nematicide reduced the N. minor population density in plots previously grown with oats, mustard, and rye. The efficacy of fluensulfone on root gall severity of cabbage was significant only in the untreated check, with plots previously grown with Image radish having a significantly lower root galling than the mustard, rye, and weedy fallow. Nematicide application reduced root gall severity of cabbage in plots previously grown with radish, Tachiibuki oat, and rye compared to the untreated check. Growing cabbage after cover crops and using the nematicide did not impact cabbage yield compared to the untreated check. These results indicate that cover cropping with Tachiibuki oat and the use of non-fumigant nematicides appear to be effective for managing these nematode species.

In the Great Plains region of the United States, perennial clover living mulch is being explored for the potential benefits of reducing tillage, suppressing weeds, and supplementing soil. Perennial living mulch systems also have the potential to reduce the use of single-use plastic. Research on the use of perennial living mulch in vegetable systems has been limited in the Great Plans, and farmers have expressed interest in trialing this system to improve soil health and reduce erosion by wind and rain. Two vegetable farms, Haroldson Farms in Bruce, SD and Blue Sky Vegetable Company in Worthing, SD, have participated in the on-farm trials since 2023. In collaboration with South Dakota State University, the on-farm trial collaborators were interested in using living mulch to control weeds and reduce the need for plastic. ‘Domino’ white clover (WC) (Trifolium repens), and ‘Dynamite’ red clover (RC) (Trifolium pratense) are the clovers that were selected for the on-farm trials. The clover struggled to grow with the lack of rainfall and was soon overtaken by weeds. Results quickly showed that the lack of moisture had a detrimental effect on the clover’s ability to compete and establish in walkways. A mixture of grasses and broadleaf were observed as the clover declined. Early moisture is essential for the establishment of clover living mulch and be used to its full potential. The planting method of frost seeding would be recommended for future trials to encourage clover germination and establishment before weeds get large enough to compete.

This study aims to evaluate the efficacy of roller crimper technology in tandem with various cover crop mixtures for weed management in coastal California's vegetable systems. The experiment was conducted at the Rodale Institute California Organic Center (34.220453, -199.108214) in Camarillo, CA. Twenty randomized plots 46 x 12 m were measured and assigned to either to a bare soil treatment or one of two cover crop mixes: oat (Avena sativa) hairy vetch (Vicia villosa), or oat pea (Pisum sativum), with cover crops terminated via conventional tillage using a disk (T) or using a roller crimper for no-till system (NT). Pumpkins (Howden variety) were direct seeded, and data on cover crop growth and weed pressure were collected at three time points: before cover crop termination, after cover crop termination and after harvest. At harvest, a subset of each plot was sampled to count and weigh pumpkins for crop yield assessment. Before termination, the total dry matter of cover crop biomass showed no significant differences between oat/peas and oat/vetch mixes. Oat/vetch exhibited lower weed biomass at 0.74 t/ha compared to oat/peas at 1.98 t/ha (0.8 t/a); bare soil plots had the greatest biomass at 21.35 t/ha. After termination (30 DAT), NT plots showed similar biomass production between oat/peas and oat/vetch. T plots displayed residues on the soil surface, with higher amounts in oat/vetch at 8.7 t/ha compared to oat/peas at 8.4 t/ha. Weed emergence after cover crop termination was comparable across all plots with cover crops, ranging from 1.24 t/ha to 2.22 t/ha, while bare soil exhibited higher weed biomass at 10 t/ha compared to plots with cover crops. After harvest (120 DAT), oat/vetch in NT plots showed greater biomass retention compared to T plots, as did oat/peas in NT plots. All plots experienced biomass reductions, with oat/peas T plots experiencing the most significant decrease at 61.5%. Oat/vetch mixture plots (T and NT) and bare soil had similar pumpkins production per hectare, outperforming oat/pea T plots in terms of fruit number and production per hectare. Oat/pea T plots exhibited decreased fruit weight compared to bare soil.

The high organic matter (muck) soils in the Holland Marsh, Ontario, Canada, are prone to wind erosion, especially in the fall and winter months. Good canopy coverage of ideally 30%, is important for protecting the soil and reducing soil erosion. Carrots are usually harvested in October. Cool temperatures at this time result in slow germination and growth of cover crop species. Field trials were conducted to assess the efficacy of various cover crops and methods for rapid establishment after carrot harvest. One approach to increasing germination and emergence is seed priming. Seeds of barley, oats, and triticale were primed by soaking for 24 hr in water (hydro-priming) or potassium nitrate at 5 mg L-1 (osmo-priming). Seed was dried for 24 hours and then seeded into pots placed in controlled environments at 5, 10 or 21°C. Priming generally resulted in faster germination and higher biomass especially at lower temperatures of 5 and 10°C. Primed and non-primed seed was seeded into high organic matter soil (50% organic matter, pH 6.9) on 17 Oct. and crop growth was assessed on 13 Nov. There were no advantages of priming in the field trials. Non-primed barley had high or higher canopy coverage (13%), plant counts and dry weight, compared to other species and primed seed. Barely was also grown as transplants with 2 seeds/plug and transplanted in the trial on 17 Oct. This treatment had higher canopy coverage (25%) and dry weight than seeded treatments. However, using barley transplants is not a cost effective option at this time. In a separate trial on an adjacent site, barley was over-seeded into standing carrots on 27 Sept. at 200 kg ha-1, and the carrots were harvested on 17 Oct. Barley and fall rye were direct seeded on 17 Oct. Pre-harvest seeding of barley resulted in significantly better establishment, canopy coverage and biomass, although all were low, maximum 12% coverage. There was a strong positive correlation between canopy coverage and biomass production across all trials. More research is needed on cover crops species and establishment methods.

On research farms on which vegetable crops are studied, there is often a need to aggressively maintain and improve soil health, while also keeping fields ready to be assigned to research projects. We tested a protocol for keeping a Northeast farm in an appropriate condition by alternating a winter cover crop of cereal rye and a summer cover crop of forage sorghum-sudangrass with no tillage. The alternating cycle was flexible for entry points when vegetable researchers finished with an experiment, as well as for exit points to make the ground ready for an experiment. Rye was sown in late September in Geneva, NY with a no-till drill and allowed to grow to anthesis in May. Sorghum-sudangrass was sown in mid-June with the no-till drill. We tested how much nitrogen fertilizer was needed to obtain a desirable amount of growth (3 tons/acre dry mater) in the sorghum- sudangrass. The trial was done in four fields using 0, 20, 40 and 60 lb N broadcast on the rye residue at planting. The highest rate is as much as our farm would agree to invest in a cover crop, but also below forage-crop recommendations. The biomass when growth stopped due to cold (Sept 18) responded strongly to nitrogen. Without nitrogen, the biomass was only 0.5 T/ac. At 60 lb/ac, the biomass ranged among fields from 2 to 4 T/ac. Nitrogen limitation was also assessed using a SPAD chlorophyll meter. The leaves in the 0, 20 and 40 lb/ac were yellow (SPAD 22-28), with the top N rate notably greener (SPAD 30-35). The fully green control had a SPAD value of 40. The cover crop rotation kept the field in a condition where is could be prepared to being a research project with about a month’s advance notice. However, to get sufficient growth of the summer cover crop, additional nitrogen is needed. This farm is on a high-fertility silt loam, but with low organic matter from repeated research trials. In that situation, at least 60 lb/ac of actual N is needed for the cover crops to meet biomass expectations.

Sweet corn is an important processing crop in the upper Midwestern United States. It can be insured for hail losses, but actuarial tables are based on field corn. The first step in developing accurate yield loss assessments is determining yield loss due to complete plant loss. To that end, we compared ear yield of sweet corn thinned to 75, 50, or 25% of a full population at three times throughout the growing season to control plots that were not thinned. We repeated this in three consecutive years at two locations, without irrigation or supplemental fertilizer. Average yield for control plots was 16.4–20.3 Mg•ha-1. Average yield losses due to thinning were generally less than currently-used actuarial estimates. For example, average yield of sweet corn when thinned to 50% of a full population at growth stage V3–V5 was 88–96% (95%CI) of full yield. The actuarial estimate is 78% of full yield, indicating greater resilience than expected. The number of tillers per plant was greater in all thinned plots, especially those thinned early in the season. Kernel recovery was unaffected by thinning treatment in one location and declined slightly at heavy thinning in the other location. Sweet corn actuarial tables should be different from actuarial tables based on field corn.

Red-winged blackbirds (Agelaius phoeniceus) and European starlings (Sturnus vulgaris) cause significant damage to sweet corn (Zea mays). Even minor damage can render ears unmarketable and the need to sort out damaged ears during packing increases costs for growers. Propane cannons and pyrotechnics have long been the preferred methods for preventing birds from damaging corn, but both methods create noise pollution and conflicts with farm neighbors. Automated laser scarecrows and automated recordings of bird distress and predator calls are two newer technologies for deterring birds from crops. We tested both technologies on a research farm in Kingston, Rhode Island and in commercial processing sweet corn fields in western New York in 2022 and 2023. All experiments used naturally occurring flocks of wild birds; flock size and species makeup varied between fields and over time. The automated laser scarecrows (LS) were designed and built by the URI Laser Scarecrow Project; they utilized a 50 mW 532 nm green laser with a beam diameter of 14 mm at the aperture and a dispersion of 4 mrad. Vertical and horizontal movement of the beam was randomized by a microcontroller. Bird Gard Super Pro units (BG) randomly played digital recordings of distress and alarm calls of red-winged blackbirds and European starlings and hunting calls of hawks and falcons. Data were collected as counts of damaged ears and converted to percentage of total ears for analysis. In Rhode Island the effect of laser scarecrow alone was compared to the effect of the laser scarecrow combined with the bird distress calls. In New York the two deterrent treatments were also compared to an unprotected control. In Rhode Island in 2022 bird damage averaged 20.7% with just LS and 7.1% with LS BG; the difference was significant at P

Cover crop biomass can provide nitrogen (N) to a sequential cash crop as a ‘green manure’, whether the N is sourced from the atmosphere or from the soil. For short-season vegetable crops in Minnesota, like transplanted broccoli, there is time for a cover crop to be grown before or after the main crop. Growing a pea-oat cover crop early in the spring, before broccoli, may increase the N available to the broccoli. However, immobilization of green manure N may reduce N availability at a time of high N demand in broccoli. In order to study N availability to broccoli provided by a spring-planted pea-oat cover crop mix, four reduced-rate nitrogen treatments were applied to two broccoli hybrids (‘Green Magic’ or ‘Gypsy’) after a spring-planted pea-oat cover crop was incorporated. Yield and maturity of broccoli were compared to broccoli grown without green manure and given a full nitrogen rate (170 kg N / ha). The fertilizer treatments included slow-release urea (139 or 110 kg N / ha), composted poultry litter with blood meal at ~110 kg N available / ha, and turkey manure applied with blood meal in the autumn before growing green manure and broccoli (~110 kg N available / ha). There was no reduction in total yield (7900 kg / ha) or marketability (>95%), but maturity was delayed by ~2 days for most treatments. A microbial inoculant (Nature’s Source®) applied to the soil at planting did not have a measurable impact on any response.

One of the most effective management strategies for controlling black rot (Xanthomonas campestris pv. Campestris (Xcc)) in cabbage (Brassica oleracea var. capitata) is resistant cultivars. The objectives of this research were to evaluate commercial and experimental cabbage cultivars for black rot resistance and determine yield potential, harvest maturity, and head quality. A field experiment with nine cultivars (1488, Capture, Celebrate, Cheers, Expat, Melissa, TCA-576, TCA-606, and TCA-607) was carried out during the fall season of 2023 at Hort Hill research farm on the University of Georgia, Tifton campus. ‘Cheers’ (commonly grown high-yielding cultivar), ‘Capture’, and ‘Expat’ (claims high resistance to black rot), and ‘Melissa’ (black rot susceptible Savoy cabbage) were used as checks for comparison with other F1 cabbages. Plants were spray-inoculated with Xcc (250 ml of 10^6 CFU/ml) at 5 and 7 weeks after transplanting. Treatments were arranged in a randomized complete block design with four replications. Relevant agronomic practices, such as irrigation, fertilization, and insect management, were implemented uniformly across all plots. Black rot severity was rated using a 1-9 scale, where 1 indicates the most resistant and 9 represents the least resistant (most susceptible) cultivar. The trial was harvested four times on the following dates:11/30/2023, 12/12/2023, 12/20/2023, and 01/03/2023. Black rot severity, total head counts and weights; and average head weight and height: and average core height, and width were statistically significant between treatments. ‘TCA-607’ and ‘Capture’ had the highest resistance to black rot disease, while ‘1488’ was the most susceptible. All other cultivars expressed moderate levels of resistance. In the first harvest ‘Cheers’ and ‘TCA-607’ had the highest total marketable head counts and weights, indicating early maturity. In addition, ‘Cheers’ and ‘TCA-607’ cabbage had the highest total marketable head counts and weight, followed closely by ‘TCA-606, ‘Celebrate’, and ‘1488’. ‘Cheers’ and ‘TCA-607’ had the highest average head height. Furthermore ‘TCA-607’ outperformed all the cultivars for the average head weight. Among all the cultivars ‘Melissa’ and ‘Expat’ performed the worst for total marketable counts and weights. Overall based on our trial, the experimental cultivar ‘TCA-607’ has the best combination of traits: best black rot resistance, highest yields, and biggest heads.

Plant growth performance of 35 different broccoli cultivars was assessed during the Fall season 2023 in terms of plant growth and head development in SW Florida. In particular, seeds of Brassica oleracea var. italica genotypes that were obtained from USDA, ARS, Plant Genetic Resources Unit (PGRU)