ASHS 2024 Conference

Onions are a key crop in the United States. In 2023, 138,000 acres were cultivated in the country with onions. Georgia harvested 11,700 acres in 2023, reaching an average production of 129,000 tons. The onion transplanting process is crucial to the crop cycle and is directly linked to the production potential and quality of the bulbs. Every year, thousands of workers are employed to transplant onion seedlings, which results in a wide variation in operational performance and quality of execution between them. These factors are influenced by the experience and conditions in which the workers operate, which can lead to failures in the process, such as double plants, partially transplanted and plants that have fallen to the ground. Furthermore, manual work is slow and requires many workers, increasing the cost of the operation. Therefore, we aimed with this study to assess the time required to manually transplant onions, the quality of manual transplanting, and the impact of inadequate transplanting on crop development. To assess how much time it takes to transplant an acre of onions, and the quality of transplanting, twenty-five people were observed during their work at a commercial field in Glennville-GA. To assess the impact of poor-quality transplanting, an experiment was carried out in four 10ft replications (10x4ft beds) in Reidsville-GA, simulating four situations observed in the commercial field. Treatments were: T1: 25% of the plants in the plot laying on the ground, T2: 25% partially transplanted, T3: 100% properly transplanted, T4: 25% multiple transplanted, T5: 100% laying on the ground. The difference in operational efficiency between workers exceeded ~20 hours per acre. Results indicated that, in average, one person transplanted 1 acre in approximately 30 hours. The fastest person in the crew transplanted in 22 hours, while the slowest took around 40 hours to transplant 1 acre. Poor-quality transplanting of seedlings exceeded up to 11%. The average number of multiple seedlings was 1%, partially transplanted seedlings was 6%, and laying on the ground was 5.5%. Plant development was assessed based on the number of leaves. Properly transplanted seedlings generated a greater number of leaves compared to the other treatments. Higher leaf number was observed in treatment 3 with an average of 7.33 leaves per plant. All the treatments differed from treatment 5, which had an average of 4.6 leaves per plant. Results indicate that good practices on transplanting can increase onion yield.

The predominant cucurbit vegetable crop during fall in Georgia is summer squash with production value of around $94.08 million on 7,757 acres in 2022 while winter squash acreage was insignificant. Whitefly and whitefly-transmitted viruses (WTV) account for 30-50% summer squash yield losses on average and threaten squash production during fall in the region. Cucurbit leaf crumple virus (CuLCrV), Cucurbit yellow stunting disorder virus (CYSDV) and Cucurbit chlorotic yellows virus (CCYV) are the prominent WTV in southern Georgia. We carried out an experiment during fall 2023 in Tifton, Georgia to evaluate tolerance of winter squash varieties for whitefly and WTV and to study their potentiality for fall production in the region. We compared ten commercial hybrid varieties of which two were acorn types (‘Tay Belle’ and ‘Table Ace’), five were butternut types (‘Waltham’, ‘Ceres’, ‘Atlas’, ‘Ultra HP’ and ‘Genesis’), and one each of a hubbard type (‘Golden Hubbard’), a kabocha type (‘Sweet Mama’) and a calabaza type (‘La Estrella’). We collected data on whitefly number, silver leaf disorder, virus incidence and severity, and fruit yield. In addition, we ran quantitative polymerase chain reaction (qPCR) and quantitative reverse transcription polymerase chain reaction (RT-qPCR) on leaf samples to detect and quantify viruses. There were significant differences between winter squash varieties for whitefly feeding preference, silver leaf disorder, virus severity, virus loads and marketable yield. ‘La Estrella’ had the lowest number of whitefly adults per cm2 leaf area followed by all other butternut types (Genesis, Ultra HP, Waltham, Ceres, Atlas), and highest in ‘Tay Belle’, followed by ‘Table Ace’ and ‘Golden Hubbard’. We found significantly severe leaf silvering in ‘Golden Hubbard’ and ‘Sweet Mama’ followed by acorn types. We observed 100% virus incidence in all the varieties, however severity was lowest for ‘Ceres’, ‘Genesis’, ‘La Estrella’, ‘Sweet Mama’, ‘Ultra HP’ and ‘Waltham’. CCYV loads was found highest in ‘Sweet Mama’ and lowest in ‘Genesis’, ‘La Estrella, ‘Ceres’ and ‘Ultra HP’. CYSDV and CuLCrV loads were highest in ‘Table Ace’ and ‘Tay Belle’ and negligible in other varieties. We observed the highest marketable fruit yield in ‘Ceres’ (7,139 count/acre) and ‘Genesis’ (7,109 count/acre). Although ‘La Estrella’ was less infested with whitefly and WTV, it had poor fruit yields. Overall, we found butternut types mainly ‘Ceres’ and ‘Genesis’ as potential alternative cucurbit vegetable crops for fall production in southern Georgia with lower whitefly and WTV infestation resulting in the highest marketable fruit yields.

Destany Westlake, Paul Fisher, Josh Tebow, and Ryan Dickson Maintaining nutrient balance in hydroponic systems reduces the need to dump nutrient solution, thereby reducing water and fertilizer cost, and the resulting environmental impact. Laboratory testing to monitor nutrient concentrations is reliable, however it typically requires shipment and days to weeks of processing. The objective was to test the accuracy of handheld and inline ion-selective nitrate and potassium sensors compared with laboratory analysis of these nutrients. The methodology consisted of a factorial design with four reservoirs containing two water qualities and two fertilizer recipes with one nutrient film technique (NFT) system per reservoir. Nitrate and potassium concentration was measured twice per week during a 6-week hydroponic trial with basil, using handheld sensors, inline sensors, and Lachat QuickChem 8500 Series 2 analysis by a commercial horticulture laboratory. Based on the laboratory testing, NO3-N ranged from 142 to 272 mg.L-1 and K ranged from 111 to 271 mg.L-1 during the trial. The average error ± one standard deviation for the handheld sensor minus the laboratory concentration was -26.5 ± 18.8 mg.L-1 and -9.4 ± 13.1 mg.L-1 for N and K, and for the inline sensors was 3.5 ± 27.5 mg.L-1 and -15.2 ± 32.1 mg.L-1 for N and K, respectively. Therefore, we conclude that the handheld and inline sensors provided a useful and rapid estimation of N and K levels, but replicated samples should be taken and these levels should be verified by periodic laboratory analysis. Onsite testing could be an important tool for effective nutrient management to reduce nutrient loss and waste.

Grafting is an effective management strategy in watermelon crop against soil borne pathogens. Carolina strongback (SB) rootstock used for grafting, is resistant to both fusarium wilt and root knot nematodes which are devastating soil borne pest of watermelon. In addition, recent studies have shown higher vigour of SB grafted plants than regular nursery plants. However, grafted watermelon nursery is 4-5 times more expensive than regular nursery which leads to reluctance among farmers for adoption of this effective management strategy. Further, recent trials showed that grafted plant bear fruits 7-10 days later than regulate plants leading to farmers losing early profitable watermelon market. To fill these gaps for informed adoption of SB grafted nursery, a field experiment was conducted at Blackville SC with the objective to evaluate the optimum transplanting time and density of SB grafted watermelons nursery to have equivalent fruit yield and harvesting window to that of regular nursery. The experiment comprised of three transplanting times and four transplant densities in a split plot design. We will evaluate the impact of transplanting time and transplanting density on watermelon fruit yield, fruit quality, number of fruits per plant, periodic fruit harvesting yield and plant vigour.

The cultivation of specialty crops in soilless growing systems has emerged as a pivotal practice in modern agriculture. The adoption of container-based production, particularly through soilless culture systems, is witnessing a significant uptrend among specialty crop producers. The challenges associated with cultivating plants in containers are extensively documented, particularly in navigating the delicate balance between insufficient and excess water. Shallow containers often result in excessive water, limiting air availability, while the confined volume of containers imposes restrictions on the water supply for optimal plant growth. Air and water capacity (AWC) model was utilized to determine basic physical properties, such as total porosity (TP), air space (AS), and container capacity (CC), for a substrate in specific-sized and shaped containers. AWC models offer a comprehensive tool for estimating hydrophysical properties across multiple substrate/container combinations simultaneously. The existing literature lacks direct reporting on these specific container types, primarily focusing on modeling the air and water profiles of traditional containers that the floriculture industry utilized, leading to a notable gap in data concerning the dynamic interplay between air and water profiles within these containers and their impact on the rooting environment. 19 substrates and 30 commercially used container selections were modeled to understand their air-water profiles. The results underscore the effect of container geometry on substrate air-water profiles, necessitating different management approaches for the same substrate in different containers. Container height stands out as a critical factor, exerting a substantial influence on substrate characteristics and subsequently affecting air and water values.

Global growing media demand is projected to increase 400% by 2050. Growers are interested in alternative substrates due to the restrictions placed on peat harvesting, as well as transportation and supply chain issues associated with peat. Kenaf (Hibiscus cannabinus), a tropical fibrous plant that was grown and composted in Florida, was evaluated to determine its potential as a horticultural substrate. Research trials were conducted in South Florida to determine effectiveness of kenaf as an alternative substrate for seed germination and plant establishment when compared to a commercially available compost and commonly used growing media. Seed germination trials consisted of planting arugula (Erica sativa) in seed trays filled with either (1) kenaf compost [KC], (2) commercially available compost [CC], or (3) ProMix HP [PM]. Germination was monitored daily, and mean emergence was determined. To evaluate plant establishment, a container trial was conducted using Lantana (Lantana camara) plants that were originally planted in Metro-Mix and transplanted from 1-gallon to 3-gallon plastic containers filled with either KC, CC or PM. Plant visual quality, percent wilt and volumetric water content(VWC) were evaluated weekly and root biomass was determined when plants were deconstructed at the end of the three-month trial. Results show that there were no treatment differences for percent seed emergence of arugula, with all emergence reaching over 80%. Plant establishment in the first field trial found KC and CC treatments increased VWC when compared to PM. Higher visual quality ratings of plants in KC and CC substrates may be explained by the increase in VWC. Lantana plants transplanted and grown in KC were uniform and grew equally as well as CC and better than PM on 13 of 14 rating dates. These data show there is no difference in arugula seed emergence when planted in CC, PM or KC. Lantana establishment in KC was comparable in CC and better than in PM growing media.