ASHS 2024 Conference

Prohexadione Calcium Does Not Affect Thinning Efficacy of 1-aminocyclopropane-1-carboxylic Acid in ‘Golden Delicious’ - Annie Vogel
Carbohydrate Status of Apple Fruitlets following Chemical Thinner Application Informs Sink Strength and Fruit Set - Laura Hillmann
Performance of a reflectance spectroscopy model to predict apple fruitlet thinning efficacy - James Larson
Overexpression of the Coding Sequence of Ma1 Decreases Fruit Acidity in ‘Royal Gala’ Apple - Lailiang Cheng
Striking the Right Balance: Innovative PGR Strategies for Fruit Drop Mitigation and Color Enhancement in Apples - Sherif Sherif
Rapid Fruit Growth Rates of Honeycrisp Apples Cause Premature Dysfunction of Xylem, Reduced Peel Calcium, and Increased Susceptibility to Bitter Pit - Chayce Griffith
Carbohydrate And Nitrogen Storage Are Inversely Affected By Crop Load For 'Honeycrisp' And 'Gala' Apples - Thiago Campbell
Impacts of Rootstock and Crop Load Adjustment on Fruit Quality and Mineral Nutrients in ‘Honeycrisp’ Apple - Esmaeil Fallahi

Apple’s (Malus × domestica Borkh.) tendency towards biennial bearing necessitates management strategies such as fruit thinning and vigor control. Applications of plant growth regulators to manage crop load and vigor overlap in the spring. A precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC; Accede®) was recently registered as a chemical fruit thinner in the USA. Prohexadione-calcium (P-Ca) is a gibberellin biosynthesis inhibitor widely used to manage vigor. It is suspected that P-Ca may interfere with ACC precursors, decreasing thinning efficacy of ACC. We evaluated the effects and interactions of ACC and P-Ca on shoot growth, ethylene evolution, leaf area, and yield responses of mature ‘Golden Delicious’. The experiment was conducted in 2023, in Mills River, NC, USA. Treatments included ACC (400 mg∙L-1), P-Ca (250 mg∙L-1), ACC P-Ca, and an untreated control. Application of P-Ca occurred on three dates. ACC was applied when average fruit diameter was ~20 mm. Across all measured responses, there were no interactions between ACC and P-Ca. P-Ca had a negative main effect on shoot growth rate (48.7–75.4% reduction). ACC reduced leaf number of spurs 4 and 9 days after treatment (DAT). Ethylene evolution in fruit and spurs was increased by ACC 1, 4, and 9 DAT (spur: 1.1e4%, 5300%, and 515%, respectively; fruit: 9200%, 725%, and 222%, respectively). ACC had a negative effect on fruit number, yield, and crop density (60.1%, 56.5%, and 60.3% reduction, respectively). These results indicate that ACC and P-Ca can be used simultaneously to manage crop load and vigor, respectively

Crop load management of apple (Malus x domestica Borkh.) is one of the most important orchard management practices to ensure adequate fruit size and quality. Fruitlets are most sensitive to thinner applications early in the season, between 6mm and 20mm fruitlet diameter. During this time, abscission is associated with environmental and biological factors that influence fruitlet development, growth and sink strength. The carbohydrate economy of the fruitlet and its position within the cluster (king flower vs. lateral flowers) are primary factors contributing to the sink strength of individual fruitlets. We evaluated the relationship between the non-structural carbohydrate status of apple fruitlets in three different size classes (i.e., 90th, 50th, and 10th percentile of the population) and their respective likelihood to persist throughout the season. Persistence probabilities of these size classes were generated by an empirical fruit set prediction model based on the distribution of fruitlet mass and confirmed by actual measures of fruit set. Soluble carbohydrates and starch were quantified with an enzymatic assay procedure. Following chemical thinner application, the concentration of soluble sugars (glucose, fructose, sucrose, and sorbitol) was significantly reduced on a gram / gram fresh weight basis. Fruitlets in the 10th percentile generally had the lowest concentration of soluble sugars and starch and the slowest recovery rate following chemical thinner application. Fruitlets in the 90th percentile generally had the highest concentrations of soluble sugars and starch. Our data support that differences in the carbohydrate concentration of fruitlets contribute to their sink strength and abscission fate as predicted by a fruit set prediction model.

Post-bloom apple chemical thinning relies on the application of plant bioregulators to induce fruitlet abscission, reducing crop load to improve fruit quality and promote return bloom. Abscission rates following chemical thinner application are influenced by carbohydrate status of the tree and thus widely variable. Multiple applications are often needed for growers to reach a desired crop load. However, trees are only perceptive to chemical thinners for a 3 to 4 week period shortly after bloom. Rapid prediction of chemical thinner efficacy is critical to allow growers to make necessary applications in this narrow period of time without the risk of over-thinning. In 2021 and 2022 a predictive model using reflectance spectroscopy measured with a handheld spectrometer (Felix F-750; Felix Instruments; Camas, WA, USA) was developed to predict chemical thinner efficacy for ‘Honeycrisp’ in North Carolina, USA. This model was found to predict chemical thinner efficacy with greater than 85% accuracy as early 3 days following a chemical thinner application. In 2023 and 2024 validation of this model occurred on multiple cultivars: ‘Red Delicious’, ‘Granny Smith’, ‘Gala’, and ‘Fuji’; and in multiple growing regions: Michigan, New York, and North Carolina, USA. Performance of the developed model to predict chemical thinning efficacy in this wide range of situations will be discussed to determine commercial applicability of the model.

Vacuolar accumulation of malic acid, the predominant organic acid in apple (Malus domestica) and many other fleshy fruits, largely determines fruit acidity, a key trait for fruit taste and flavor. ALUMINUM-ACTIVATED MALATE TRANSPORTER 9 (ALMT9/Ma1) underlies a major genetic locus, Ma, for fruit acidity in apple. A natural mutation at base 1455 leads to a pre-mature stop codon that truncates the Ma1 protein by 84 amino acids to ma1, and this truncation significantly reduces Ma1’s malate transport activity by disrupting a conserved C-terminal domain, leading to low fruit acidity in recessive homozygous ma1ma1 genotypes. However, it remains unclear how Ma1 functions to transport malate across the tonoplast membrane. When the coding sequence of Ma1 was overexpressed in ‘Royal Gala’ apple (Ma1ma1) to determine its in planta function, to our surprise, the transgenic fruit had drastically reduced fruit acidity compared with the wild-type (WT). This led us to uncover that Ma1 undergoes alternative splicing. Two isoform proteins are generated by alternative splicing: Ma1beta being 68 amino acids shorter with much lower expression than the full-length protein Ma1alpha. Ma1beta does not transport malate itself, but interacts with the functional Ma1alpha, creating synergy with Ma1alpha for malate transport in a threshold manner when Ma1beta is equal to or exceeds 1/8 of Ma1alpha. In WT ‘Royal Gala’, Ma1 operates at this threshold. Overexpression of Ma1alpha triggers feedback inhibition on the native Ma1 expression via transcription factor MYB73, decreasing the Ma1beta level well below the threshold that leads to significant reductions in Ma1 function and malic acid accumulation in fruit. Overexpression of Ma1alpha and Ma1beta or genomic Ma1 increases both isoforms proportionally and enhances fruit malic acid accumulation. These findings reveal an essential role of alternative splicing in Ma1-mediated malate transport underpinning apple fruit acidity.

Biennial or alternate bearing is characterized by an abundance of blooming and fruiting in “on” years and a lack of blooming and fruiting in “off” years. Biennial bearing in fruit tree production has been extensively studied. However, it continues to be problematic in certain crops and cultivars. Fundamental physiological mechanisms controlling this behavior are still poorly understood. Along with carbohydrates in plant tissues, reserve nitrogen influences early-season growth in apples, with the percent contribution of reserve nitrogen being dependent on the current nitrogen supply. Because flowering and fruit set occur in spring alongside bud break, reserve nitrogen can significantly affect these processes too. We sought to understand the role carbohydrate and nitrogen storage in various plant tissues has on biennial bearing for ‘Honeycrisp’ apple. Apical buds, terminal shoots, and one-year-old spurs were collected in 2022

In apple orchards, addressing pre-harvest fruit drop in early-maturing, commercially valuable cultivars like ‘Honeycrisp’ and ‘Gala’ is crucial. This issue is largely linked to ethylene, a ripening hormone that, despite its role in enhancing fruit qualities, triggers premature fruit drop. From 2018 to 2021, extensive field trials were conducted across commercial and experimental orchards to refine the application of two ethylene-inhibiting products, ReTain (AVG-15%) and Harvista (1-MCP-1.3%), in mitigating this challenge in ‘Gala’ apples. Our findings confirmed AVG’s effectiveness in reducing fruit drop and stem-end splitting; however, AVG application consistently resulted in diminished fruit coloration. In the subsequent seasons of 2023 and 2024, our research pivoted towards identifying plant growth regulator (PGR) formulations that could balance the dual objectives of minimizing fruit drop and preserving color development in ‘Honeycrisp’ and ‘Gala’ apples. Key findings include: a) the multiple applications of Accede (ACC-10%) and Motivate (Ethephon-21.7%) starting from three weeks before harvest significantly enhanced red color formation in ‘Honeycrisp’ and ‘Gala’ apples, surpassing control and ReTain treatments, though Motivate increased the rate of fruit drop; b) ReTain, both alone and in combination with Accede, notably reduced fruit drop, with the ReTain-Accede mix also enhancing fruit coloration; c) combining ReTain and Motivate neither decreased fruit drop nor enhanced color; d) the positive impact of the ReTain-Accede mix on color was biochemically and molecularly validated; e) Accede's color-enhancing effect appears to be ethylene-independent. This research underscores the potential of specific PGR mixes in achieving a harmonious balance between reducing fruit drop and enhancing fruit coloration.

The influence of rootstock and time of crop load adjustment on ‘Honeycrisp’ apple fruit quality at harvest and after storage was studied over four seasons. Yield per trees varied from year to year because of biennial bearing. Trees on V.1 and G.30 were higher while those on G.969 often had lower yield per tree. Fruit from trees on M.26EMLA and G.30 were larger, while those on G.202 and G.969 were smaller than those on other rootstocks in two of three years. Fruit firmness at harvest and after storge was often inversely proportional to their size, so that fruits from trees on G. 202 often had higher but those on G.30 often had lower firmness at harvest and after storage. Percentages of fruit bitter pit among rootstocks at harvest was different than those after storage. However, fruit from trees on M.26EMLA, V.1, and G.30 generally had higher bitter pit than those on G.969 and G.202 rootstocks. Fruit fresh weight continually grew during growing season. However, the increase in percentage fruit dry weight reached a plateau on August 9, after which it leveled off. Trees receiving an “Early Heavy Thinning” and “Thinned Early to 1 Fruit/bunch” had lower yield but larger fruit with more bitter pit than Un-thinned-Control trees. Trees receiving a thinning on June 11 and June 25 had similar fruit size in the same season. However, bitter pit was increased, while fruit size decreased, as the hand thinning was delayed until July 8. Late hand thinning resulted in smaller fruit size with less bitter pit. Fruit potassium/ calcium (K/Ca) ratio did not change significantly between June 20 and August 8 within the same year. This research unveils importance of rootstock, time, and level of and thinning in the fruit quality of ‘Honeycrisp’ apple.

Insufficient transport of calcium to and throughout the cortex of apple is a primary factor contributing to bitter pit, a disorder characterized by dark lesions on the fruit surface. Calcium transport, in-planta, occurs solely in the xylem. Progressive transport dysfunction of xylem limits calcium concentration in the peel and subtending tissue. Rapid fruit growth may accelerate xylem dysfunction due to the stretching, shearing, or compressing of xylem elements. The relative time course of these events and subsequent effect on calcium concentration of peel tissues is not well understood. Growth rate of fruit was manipulated by manually adjusting the crop load of 6th leaf ‘Honeycrisp' trees to either 4 (low), 8 (moderate), or 16 (high) fruit per cm2 of trunk cross-sectional area via bud extinction. Fruit mass, xylem functionality, and peel calcium content were assessed weekly throughout the season. Fruit tissues were frozen weekly to evaluate the expression of genes related to xylogenesis and calcium transport and for quantification of hormones. At maturity, 25 trees were harvested from each crop load treatment. Fruit were assessed for bitter pit, stored for three months in regular air (3⁰C), then reassessed. Crop load influenced both xylem functionality and bitter pit incidence of fruit. Low crop load fruit lost 80% of xylem functionality by 8 weeks after bloom, which was two weeks earlier than moderate crop. By seven and five weeks before harvest, total xylem dysfunction was observed in fruit of low and moderate crop load, respectively; xylem in high crop load fruit never became fully dysfunctional. Final fruit mass from low crop load trees was only 20 grams larger than fruit from moderate crop load trees, yet, these fruit had a roughly 100% increase in bitter pit incidence at harvest (27.3% vs. 12.6%). Only 4.1% of high crop load fruit were affected by bitter pit. Many previous studies have ascribed the positive relationship between fruit mass and bitter pit incidence to calcium dilution. Our data suggest, however, that the issue is one of transport limits that appear to begin very early in fruit development, exacerbated by the growth rate of fruit, resulting in less peel calcium and higher bitter pit incidence at harvest than fruit of relatively lower growth rates. Future analysis of endogenous hormone concentrations and expression of genes relating to xylogenesis and calcium allocation will facilitate a better understanding of the processes governing xylem dysfunction and its association to bitter pit disorder.

Effect of Biostimulants on Emergence and Growth of Watermelon (Citrullus lanatus) Transplants. - Evan Christensen
Evaluation of Specialty Cucumber Cultivars in a High Tunnel Production System - Jacob Arthur
Are Locally Sourced Biochar and Poultry Litter the Solution to Improving Soil Health and Sustainably Producing Tomatoes? - Emilio Suarez Romero
Is Trellising Beneficial to High Tunnel Melon Yield? - Lewis Jett
Interseeded Clover Does Not Impact Pumpkin Yield - Charlie Rohwer
Protecting New Mexico’s Chile Crops from Curly Top Virus through Agrivoltaics - Mariela Estrada
Integrating High-resolution Satellite Imagery to Monitor Crop Growth and Yield: A Case Study of Japanese Squash and Onion in Hollister, California - Elia Scudiero
A New Tool to Manage Water and Nutrients in High Tunnel Tomato Production - Rebecca Brown
Physiology of Heat Tolerant Tomatoes: Transplanting Through Harvest - Courtney DeKalb-Myers

The impacts of climate change and drought threatens water supplies that are necessary for watermelon production. Most production in the U.S. is seedless watermelon, typically grown in greenhouses and transplanted due to poor seed establishment in the field. Given the significance of high-quality transplants for the industry, we conducted a study to evaluate whether biostimulant products would improve transplant quality. In this study seven biostimulant products were tested on greenhouse-grown watermelon seedlings to measure seedling emergence and growth. Three bacterial (Continuum, Spectrum Ds, and Tribus Original), two mycorrhizal (MycoApply Endo, and Mighty Mycorrhizae), one humic (Huma Pro 16), and one seaweed extract product (Kelpak) were used. All products, except Kelpak, were incorporated into the growing media before sowing. Kelpak was applied at the first true leaf stage as a soil drench. Leaf area and root/shoot fresh and dry weight were measured over a 30-day period after stand establishment and data underwent analysis of variance (ANOVA) using SAS statistical software. Though some biostimulant products tended to have higher shoot and root weight they were not always significantly different, and the results were variable from trial to trial and analysis is ongoing.

Cucumbers are popular and high-value vegetable crops mainly marketed through local food markets for fresh consumption. Vegetable growers in Mississippi mainly operate on small to medium size farms. High value crops including tomatoes, peppers and cucumbers could be grown to increase competitiveness. Specialty cucumber cultivars including the parthenocarpic and mini types are in high demand due to their superior eating quality, these are often produced in protected environments like high tunnels or greenhouses. The objective of this study is to evaluate specialty cucumber cultivars and identify cultivars for superior yield and quality in the local climate under protected culture. This study was conducted in a high tunnel production system located at Mississippi State University through two growing seasons in 2022 and 2023. Twenty cucumber cultivars were evaluated including ten long Dutch/English slicer types: ‘Asteroid Long’, ‘Bologna Long’, ‘Boncanale Long’, ‘Davida Long’, ‘Durance Long’, ‘Georgia’, ‘Kasja Long’, ‘Tyria Long’, ‘Verdon Bio Long’, ‘Verdon Long’; five mini types: ‘Jawell Mini’, ‘Katrina’, ‘Manar Mini’, ‘Picolino’, ‘Socrates’; and four Asian types: ‘Itachi’, ‘Nokya’, ‘Unagi’, ‘Wokue’. The last cultivar ‘Striped Armenian’ is not a true cucumber and is actually part of the melon family. Plants were grown in 6-gallon containers using a modified drop line trellis system. Plant vegetative growth that was measured included plant height, stem diameter as well as soil plant analysis of development (SPAD). Cucumber fruits were harvested twice weekly, weighed for individual fruit weight, counted, and separated into marketable yield and unmarketable yield. Various fruit quality characteristics including: fruit diameter, fruit length, skin color, soluble solids content and fruit firmness were collected twice in each growing season. Cultivars varied in marketable and unmarketable yields in both growing seasons. In 2022, the cultivar ‘Picolino’ produced the highest marketable yield of 4.79 kg per plant with a majority of the other cultivars having statistically similar marketable fruit yields ranging from 2.87 kg in ‘Unagi’ to 4.75 kg in ‘Katrina’. The lowest marketable yield was produced by ‘Striped Armenian’ with 2.05 kg of marketable fruit for the entire growing season. Fruit quality parameters including soluble solids content, firmness, and fruit length had significant differences between cultivars. The cultivar ‘Kasja Long’ produced fruits with the highest soluble solids content of 4.18 °Brix, the other cultivars in this study had values ranging from 2.47 °Brix to 4.12 °Brix. The cultivars ‘Itachi’ and ‘Socrate’ produced the firmest fruit with values of 6.75 N and 6.70 N, respectively.

Agriculture is challenged by nutrient runoff, declining soil health, and high costs of inorganic fertilizers. This study investigates the potential of locally sourced biochar and poultry litter to address these issues by enhancing soil health and tomato production. Conducted in Spring 2023, the field trial assessed biochar application rates of 0, 10, 15, and 20 (tons/acre), combined with either organic (poultry litter) or inorganic fertilizer providing (225 N lbs/acre) for the growing period of the tomatoes. Utilizing a randomized complete block design, the experiment had four replications across ten treatments. The findings from this study revealed no significant differences in tomato yield between plants fertilized organically or inorganically across the various biochar application rates. Notably, the use of poultry litter as an organic fertilizer showcased promising results, particularly evident in the increased production of extra-large tomatoes. However, it also led to a higher count of culls. Biochar application significantly enhanced several key soil chemical properties, including pH levels, cation exchange capacity (CEC), and nutrient retention, especially at higher application rates. The incorporation of biochar was observed to substantially elevate soil pH by the season's end, attributed mainly to its considerable calcium content. A biochar application rate of (20 tons/acre) notably increased the pH to 6.8 in the inorganic treatment and even higher to 7.2 in the organic treatment when combined with calcium-rich poultry litter. In scenarios without biochar, the sandy loam soils exhibited a decrease in pH levels by the end of the season, indicating biochar's crucial role in counteracting soil acidification. The study also highlighted that a high biochar application rate significantly improved CEC in both inorganic and organic production systems by the season's end, facilitating better nutrient retention in sandy loam soils. Furthermore, higher biochar applications were associated with lower nitrate concentrations, while the absence of biochar in both treatments led to increased nitrate levels. This pattern was similarly observed with ammonium levels, where higher biochar applications resulted in reduced concentrations, suggesting that biochar effectively prevents the volatilization of ammonia. The research supports the hypothesis that biochar functions like a sponge, retaining essential nutrients within the soil matrix. This study provides evidence that biochar presents a viable strategy for organic and inorganic farmers to enhance soil chemical properties over the long term, offering a sustainable solution to improve agricultural practices and tomato production.

Cantaloupes (Cucumis melo var. reticulatis) are a fruiting vegetable which grow best in warm environments. Cantaloupes also are infected by many foliar diseases which are triggered or exacerbated by rainfall and high relative humidity which is common during the growing season in Central Appalachia. One potential option for growing cantaloupes in West Virginia is high tunnel production. High tunnels significantly increase the air and soil temperature. In addition, the crop can be drip irrigated so there is no wet foliage for disease infection. Trellising may be necessary to facilitate harvest. Vertical trellising with pruning may be necessary for high tunnel production. Trellising can potentially increase marketable yield. However, trellis and pruning labor can be as high as $150/1000 ft2. Cantaloupes (cv. ‘Sugar Cube’) were transplanted within a high tunnel in 2023 and 2024. Vertical trellising and pruning were compared with non-trellised and non-pruned plants. Inputs such as labor and trellising supplies were recorded. In 2023, trellising did not significantly increase marketable yield of cantaloupes, but did significantly improve harvest efficiency.

Pumpkins are usually grown using wide row spacing, and in Minnesota, the canopy does not close until mid-summer and the canopy senesces in early- to mid-autumn. This provides opportunity for establishing frost-tolerant or winter-hardy cover crops between rows before the canopy closes, which will continue to grow after pumpkin foliage is gone. To understand more about competition between interseeded cover crops and pumpkins, four species of clover (berseem, crimson, Persian, and red) were sown between pumpkin rows (10-ft spacing) in late June, and pumpkin yield and clover growth and N content were measured in the fall. Both ‘Cotton Candy’ and ‘Kratos’ pumpkins were studied. ‘Kratos’ yield (68.4 Mg / ha; 1185 fruit / ha), fruit size (9.7 kg), and fruit size variability (28%) were 1.8 times, 0.55 times, 3.2 times, and 1.1 times as much as ‘Cotton Candy’, but none of these responses were impacted by clover. Above-ground biomass of berseem, Persian, and red clovers averaged 0.41 Mg / ha in late fall (16 kg N / ha), but crimson clover yielded 1.2 Mg / ha (33.3 kg N / ha). Clover grown with ‘Kratos’ yielded 69% of the dry matter and 73% of the aboveground nitrogen (per ha) compared to clover grown with ‘Cotton Candy’. The average C:N ratio of all treatments was 18.3. These results show that clover interseeded into pumpkins, especially crimson clover, can grow successfully without impact on pumpkins. High-vigor pumpkins can reduce clover yield, however.

Chile (Capsicum annuum) consumption and production have been integral to New Mexican culture for over four centuries, and the state is the leading producer of chile (non-bell peppers) in the United States. Chile farmers face adverse conditions due to climate change, water scarcity and disease control. One of the most prevalent chile diseases in NM is Beet Curly Top Virus (BCTV; Curtovirus). BCTV causes chlorotic curled leaves, stunted growth, abnormal or minimal fruit production, and a potentially substantial yield reduction. BCTV is transmitted by beet leafhoppers (Circulifer tenellus), insects that prefer feeding in areas exposed to full sun. Agrivoltaic systems (AVS), the co-location of solar panels in agricultural fields, increases field shade. Advantages of AVS have been examined, but its potential role as a deterrent for pests remains unknown. The aim of this study was to determine the impact of AVS shade on chile yields, beat leafhopper abundance, and BCTV incidence. On 16 May 2023 ‘NuMex Odyssey’, a New Mexico pod-type green chile was transplanted into four solar panel plots and a full sun control at the New Mexico State University Leyendecker Plant Science Research Center, Las Cruces, NM. Plots shaded by solar panels had an average of 15% less light radiation compared to the full sun control. Fruit was harvested on 21 Aug 2023 and sorted into marketable green, blossom end-rot affected, and curly top affected fruit. Preliminary results show that marketable green and blossom end-rot affected fruit yields did not differ between solar panel shaded and the full sun control plots. BCTV affected fruit yield was significantly greater in the full sun control, which also had 55% more trapped beet leafhoppers than the solar panel plots. Initial results show potential for AVS as a method to mitigate the adverse effects on chile yield caused by BCTV. In addition to alleviating crop stress, AVS has the potential to deter beet leaf hoppers while generating electricity, a potential extra revenue for the farmer.

Accurate monitoring of crop growth and estimations of yield are essential for optimizing agricultural practices and ensuring food security. Traditional approaches to monitor crop and map yield in vegetable crops often rely on ground-based observations, which can be time-consuming and labor-intensive. Remote sensing techniques offer a promising alternative by providing frequent and spatially extensive information on crop health and vigor. In this study, we aimed to assess the feasibility of using high-resolution satellite imagery to monitor crop growth and predict yield in Japanese squash (Cucurbita maxima) and onion varieties (Allium cepa) in Hollister, California, over the growing seasons of 2022 and 2023. Daily imagery from PlanetScope with a resolution of 3 m and on-demand 0.5 m imagery from Planet SkySat were utilized. Vegetation indices including the Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI) were calculated at various times during the growing season. Statistical analyses were performed to explore the correlations between these indices and crop yield. The results indicate significant correlations between vegetation indices such as NDVI and SAVI and crop yield in Japanese squash and onion varieties. Higher vegetation index values were associated with increased crop yield, suggesting that these indices can serve as reliable indicators of crop health and vigor. The use of high-resolution satellite imagery allowed for timely and accurate monitoring of crop growth dynamics, facilitating informed decision-making for growers. This study describes the potential of high-resolution satellite imagery and vegetation indices for monitoring crop growth and predicting yield in Japanese squash and onion varieties. The importance of integrating remote sensing techniques into agricultural practices to improve crop management strategies and enhance productivity will be discussed in the presentation.

Much of the tomato production on market farms in the northeastern United States utilizes high tunnels. Tunnels protect soils from rainfall, reducing leaching of nutrients. However, if nutrients are accumulating below the root zone in tunnel soils lateral flow could be moving the nutrients beyond the covered area, resulting in leaching. From July 2020 to October 2022 we monitored soil moisture, soil temperature, and mineralization and movement of nitrate and phosphate in high tunnel tomato production on five commercial market farms (2 in Connecticut and 3 in Rhode Island). We also tracked irrigation water and fertilizer applications. Activated mixed-bed resin capsules were buried at 30 cm depth in transects running across the width of each high tunnel and extending 1 m past the tunnel perimeter on each side. Resin capsules were exchanged in March, July and October of each year and analyzed for captured nitrate, ammonium and phosphate. Soil P in the tunnels ranged from 16 to 363 kg/ha and soil K from 207 to

Consumers are motivated to purchase locally grown tomatoes for a maximum flavor experience. With this demand, tomatoes are highly valuable in the local food system and one of the most profitable crops for small, diversified farms. Tomato production in Oklahoma, and other warm climates, can be difficult with the fruit’s temperature requirements for fruit set. Optimum conditions are available for a short period in Oklahoma. The additional threat of climate change could present even more challenging growing conditions in the future. There are heat tolerant tomatoes available, but these cultivars still have an upper limit for stress exposure. Previous research shows that there are distinct physiological differences between heat tolerant and heat sensitive cultivars, but these evaluations focus primarily on the early stages of the plant’s development. We aim to investigate the differences in cultivars throughout the entire plant life cycle. A field experiment will include six cultivars at different planting dates, showing a range of responses. The three planting dates will impose different temperature regimes throughout plant development. Physiological measurements will be recorded at regular intervals from transplanting through harvest. These parameters will include chlorophyll fluorescence, stomatal conductance, and electrolyte leakage. The results will assist with development of a model that enhances Oklahoma tomato production capacity through optimizing cultivar selection.

Prospects for Grapes in High Tunnels - Paul Read
Growing Grapes on the Texas High Plains: A Review of Grower Concerns and Recent Research - Thayne Montague
Improving the Climate Resilience of Wine Grape Vineyards via Trellis Selection and Applied Water Amounts in Warm/Hot Viticultural Regions - Runze Yu
Heat Stress Effects on South Mississippi Grown Bunch Grapes - Haley Williams
Rethinking Chill Models: The Role of Cold Hardiness, Freezing Temperatures and Daily Fluctuation on Promoting Dormancy Progression and Release - Amaya Atucha

High tunnels have proven to be a suitable alternative for a number of small fruits and vegetables, but potential applications for grapes need to be further explored. We have conducted seven years of research with table grapes in high tunnels and demonstrated that profitable production can be achieved with the concomitant reduction of environmental challenges, including vertebrate pests, hail and extremes of weather. This approach has also resulted in less pesticides required to maintain a quality robust canopy. Furthermore, our research has shown that cold storage retains marketable quality, thus enabling extending the marketing season for the cultivars tested (Thomcord, Everest, Marquis, Mars, Canadice and Somerset). In addition, we have explored the potential of growing Vitis vinifera grapes in a high tunnel in the Midwest with the goals of enabling our commercial wineries to have a local source of grapes that are not adapted to field production in Nebraska but are desired by consumers. Vinifera grapes can thus be produced as a local wine varietal or can be employed to enrich wines made from locally adapted cultivars. Data on survival and productivity of specific cultivars such as Cabernet Sauvignon, Tannat, Petit Verdot, Riesling and other vinifera cultivars will be presented while discussing the productivity of closely related new cultivars.

Within the State of Texas the grape (Vitis vinifera) and wine industry has an economic impact of over $20 billion. Currently there are more than 3,700 ha of vineyards within the state, and greater than 80% of Texas vineyards are within the Texas High Plains American Viticultural Area (AVA). High Plains AVA grape growers are blessed with beneficial soil conditions, low biotic stress factors, and a generally favorable climate. However, geophysical challenges within the AVA include dangerous winter temperature extremes, late spring frosts, high wind speed events, thunderstorms, damaging hail, drought, and herbicide volatility and drift concerns. Despite these challenges, the Texas High Plains AVA has gained a reputation for producing high yields and fruit with exceptional quality. This presentation will focus on recent (past three years) research efforts performed by Texas A&M AgriLife Research and Extension and Texas Tech University personnel: investigating grape grower concerns associated with vine water requirements, avoiding grapevine hail damage, estimating vine cultivar bud dormancy traits, and quantifying herbicide drift and volatilization into vineyards. Presented research results benefit Texas High Plains grape growers and give growers additional insight into production practices and management methods suited for grape production within the unique Texas High Plains AVA environment.

In grape vineyards, trellis systems are used to provide specific canopy microclimate to optimize grapevine production, physiological performance, and berry composition. However, many major wine producing regions are being challenged by the constantly increasing air temperature and decreasing available water allocated for agricultural use. The objective of this study was to understand the impact of trellis system and applied water amount on grapevine productivity and grape quality. This study was conducted to evaluate six trellis systems, including a vertical shoot positioned (VSP), two modified VSP systems (VSP60 and VSP80), a single high wire (SH), a high quadrilateral (HQ), and a cane-pruned VSP-Guyot (GY) and three applied water amounts based on various crop evapotranspiration (ETc), including 25%, 50%, and 100%, in 2020 and 2021. The results showed that SH and HQ systems, once fully established, could have higher efficiency in accumulating total soluble solids (TSS) and total yield. Also, these two systems showed greater flavonol and anthocyanin accumulation in grape berry skins compared to the VSPs, possibly resulted from reduced chemical degradation from the hotter environment Being strongly correlated with canopy architecture, the flavonols and molar percentage of quercetin in berry skins, indicated that the VSP systems were more likely to be prone to overexposure and potential photooxidative stress. The three applied water amounts showed that with less water, grapevines would have lowered yield but increased berry flavonoid accumulation. Overall, this experiment provides information about selecting trellis systems and applied water amounts to optimize vineyard productivity and berry quality in warm/hot viticultural regions.

In the challenging climate of Mississippi, where high heat, rainfall, and humidity pose significant challenges to bunch grape (Vitis spp.) production, identifying resilient cultivars is essential for determining stress adaptation and sustainable agricultural practices. This study assessed the heat tolerance of nine interspecific hybrid bunch grape cultivars/selections (‘Ambulo Blanc’, ‘Black Spanish’, ‘Blanc du Bois’, ‘Lomanto’, ‘MidSouth’, ‘Miss Blanc’, ‘Muench’, OK392, ‘Victoria Red’) grown at the Mississippi Agricultural and Forestry Experiment Station South Mississippi Branch in Poplarville, Mississippi, in 2023. Stomatal density, stomatal conductance, transpiration, vapor pressure deficit, and chlorophyll fluorescence were evaluated both in the field and through leaf disks subjected to a 4-hour heat simulation. ‘Miss Blanc’ and OK392 exhibited the highest stomatal density, while ‘Black Spanish’ had the lowest. Monthly in-field measurements showed no significant differences in physiological measurements. Regarding specific cultivars undergoing the heat simulation, ‘Lomanto’ displayed elevated stomatal conductance and transpiration, contrasting with OK392 with lower values. ‘MidSouth’ showcased high chlorophyll fluorescence, whereas ‘Ambulo Blanc’ consistently displayed lower levels. ‘Miss Blanc’ and OK392 exhibited high vapor pressure deficit, while ‘MidSouth’ showed low values. Further analysis unveiled several correlations: a strong positive correlation between stomatal conductance and transpiration (r=0.9, P

This study addresses fundamental questions in bud dormancy, specifically the impact of temperature on chill accumulation and cold hardiness on dormancy release. We evaluated bud cold hardiness (CH) and time to budbreak responses of grapevines throughout chill accumulation under three treatments: constant (5°C), fluctuating (-3.5 to 6.5 °C daily), and field conditions (Madison, WI, USA), during three dormant seasons. Findings reveal that lower temperatures in chill treatments result in greater cold hardiness gains (CHfield>CHfluctuating>CHconstant). All treatments reduce time to budbreak with increased chill accumulation. However, when time to budbreak was adjusted to remove cold acclimation effects, treatment effectiveness changed. Notably, existing chill models (North Carolina, Utah, and Dynamic) fail to accurately describe adjusted budbreak responses. Our results demonstrate how chill treatment effectiveness changes when adjustments for uneven acclimation are considered. We propose a new model that includes freezing temperatures and enhances chill accumulation under fluctuating conditions.

Irrigation Management With Spreadsheets in Small Farms - Gustavo Haddad Souza Vieira
Assessing Micro-Irrigation Clogging Risk Through Water Quality Classification Systems - Juan Cabrera Garcia
Development of an Open-source, Autonomous Irrigation Controller for Horticultural Applications - Andrew Bierer
Microbial Community Composition and Accumulation Of Biofilms In Irrigation Pipes Using Nutrient Solutions with Different Organic Loads - Juan Cabrera Garcia
ATP vs Petrifilm: Techniques to Quantify Microbial Communities for Water Quality Analysis - Dharti Thakulla
Water use and crop coefficients for outdoor nursery ornamentals in 15-gal containers - Gerry Spinelli
Quantification of irrigation and stormwater runoff volume, sediment load, and nutrient load when producing nursery crops - James Owen
Water Supply Resilience Through Florida-Friendly Landscaping - Michael Dukes

In the Central Serrana region, Espírito Santo state, Brazil, there is a predominance of small farms and the technological level used is still low, especially in terms of water use. Irrigation management can provide greater water use efficiency and promote optimization of crop productivity and conservation of water resources. Thus, this study aimed to implement an irrigation management program, using simplified electronic spreadsheets, for drip irrigation, based on the climatological water balance, for family-based farmers. We selected four spots located in the towns of Barra de Bom Destino; Barra de Jatibocas; Baixo Sossego and headquarters of the Itarana County, state of Espírito Santo, Brazil, with drip irrigation systems, irrigating banana, arabica coffee, guava and conilon coffee crops. Irrigation management was carried out for seven months, using daily temperature and precipitation data, obtained from maximum and minimum thermometers and rain gauges, respectively. The values were collected by farmers, noted in tables and registered in electronic spreadsheets, which provided recommendations for irrigation times. In adjacent areas, irrigation was carried out according to its local traditional rule, in the way that farmers did before the implementation of management, with the purpose of comparing the volume of water used in the two forms of irrigation. The banana irrigator followed the irrigation management guidelines using the spreadsheet and, comparing the two areas, achieved a 7.5% increase in productivity and a 9.34% increase in water use efficiency. Farmers in areas with arabica coffee and guava managed irrigation, but were not organized to collect crop productivity data. For guava cultivation, an increase in fruit load was visible in the area with irrigation management. The Conilon coffee farmer did not follow the irrigation management recommendations, considering the task laborious and complicated. Irrigation management continues to be carried out on farms with banana, guava and arabica coffee. New neighboring producers expressed interest in using electronic spreadsheets. Work has been done on the development of new tools for irrigation management, using smartphones, to facilitate the task of calculating irrigation management. Therefore, it is expected that with the continuity of the work, the practice of irrigation management will be more widespread among farmers and they will decide to use it.

Clogging poses significant economic risks in greenhouse micro-irrigation systems. While water quality classification systems aim to assess the overall risk of clogging in micro-irrigation systems, they haven’t been evaluated for their ability to predict potential clogging based on water quality characteristics, particularly in controlled environment agriculture. Understanding these causes can inform robust thresholds and effective water management strategies to mitigate economic risks associated with clogging. This project aimed to evaluate if the existing classification systems could be used to identify the cause of clogging in micro-irrigation systems in greenhouses. Water from eight commercial greenhouses with reported clogging was analyzed for physical, chemical, and biological properties to rate the risk of clogging according to the classification systems. In general, iron and manganese from the fertilizers and high microbial load resulted in high ratings. However, the ratings lacked insight into the specific causes of clogging, disregarding interactions among chemical and microbial factors and qualitative characteristics of specific microbial phenotypes (e.g., production of polysaccharides or iron oxidation) that lead to clogging. Furthermore, the systems overemphasize nutrient levels typically used in greenhouse fertigation as the cause of clogging—which is not commonly observed in practice. Enhancing these systems requires parameters that reflect interactions among water quality parameters and the influence of microbial traits on clogging. Further research needs to develop these parameters in new systems with robust and precise thresholds in which emitter performance, profitability, and sustainability are affected.

An open-source data-driven irrigation controller, "Open_Irr", was developed by USDA-ARS as a low-cost (≤ $250 USD) entry point to autonomous irrigation installations in horticultural production and research applications. The device is reliant on granular-matrix type Watermark soil tension sensors (n≤16) from which it acts as a datalogger; sensors can be partitioned into 4 groups for water management in which readings can be used to output a logic-level signal for opening valving to initiate irrigation events. Here, we demonstrate the use of the device in research applications for imposing drought stress in containerized plantings of apple (Malus domestica). Our primary objectives were to (i) determine the utility of using granular matrix type soil tension sensors for predicting plant physiologic responses, measured by growth habit, infrared gas exchange, and chlorophyll fluorescence, for improvement of decision support systems; and (ii) determine potential differences in cultivar performance under water deficit conditions. A trial examined performance of ‘B.9’ rootstock grafted to ‘Autumn Gala’, ‘CrimsonCrisp’, and ‘Golden Delicious’ scions at set soil matric potential thresholds for irrigation events (-25, -40, -60, and -80 kPa). A second trial examined five rootstock cultivars (‘B.10’, ‘B.9’, ‘G.11’, ‘G.935’, and ‘G.969’) grafted to a common ‘Honeycrisp’ scion as plant available water contents of the soil were theoretically progressively decreased by 5% each week. Correlation matrices between aspects of physiology and soil matric potential revealed Pearson’s r ≤ |0.43| yet further regression analysis offered potentially useful data shapes warranting further exploration. A piecewise regression suggested soil matric potential could predict, to an extent (r2 = 0.29), the rate of change in leaf water potential upon exposure to water deficit. The break-point of the piecewise regression in leaf and edaphic potentials was respectively -30.6 kPa and -0.73MPa, which may prove useful for incorporation in developing irrigation decision support systems. The pattern of stomatal response to deficit suggested enhanced stomatal regulation capacity of ‘Gala’ relative to other scions in which nonstomatal factors likely contributed to short term maintenance of photosynthetic C assimilation rates. Similarly, the ‘G.935’ rootstock demonstrated superior sensitivity to water deficit through rapid stomatal closure relative to other cultivars. Refinement of the relationships between arduous measures of physiologic function with correlated easy-to-automate proxy measures is advised for potential advancement of irrigation decision support systems.

Biofilms clog irrigation systems, thus affecting water use efficiency, crop yields, and production costs. Microbial attachment and subsequent biofilm accumulation is influenced by the irrigation water quality and materials used in the design of water distribution systems. Therefore, the goal of this research was to evaluate if the pipe material and the load of organic matter in nutrient solutions affected biofilm accumulation, microbial community composition, and emitter performance. Nutrient solutions had 0, 30, 60, and 120 mg·L-1 peat particles under 150 µm in diameter and flowed through pipe loops made of polyvinyl chloride (PVC) and polyethylene (PE). The emitters were pressure compensated drippers with anti-drain mechanism and a nominal discharge of 2 L·h-1. Heterotrophic plate counts and biofilm dry mass were used as indicators of biofilm accumulation. DNA was extracted from the biofilm then sequenced for bacterial community composition analysis. The surface of new and post-biofilm pipes was characterized by measuring hydrophobicity and roughness to evaluate the effects of biofilm on the pipe’s surface. None of the emitters clogged, but there was an increase in discharge with 60 and 120 mg·L-1 peat. This observation suggests that the particles and biofilm accumulation affected the operation of the emitters’ anti-drain mechanism. The pipe material had more influence on the accumulation and bacterial community composition of biofilms than the organic load of the nutrient solution. Overall, biofilm accumulated more on PVC pipes than on PE pipes. The hydrophobicity of PVC pipes decreased, and roughness of PVC and PE pipes increased after biofilm colonization. These results suggest that the characteristics of the pipes can influence and be influenced by biofilms and therefore affect the risk of clogging. Our results also suggest that biofilms establish better on materials that biodegrade easy and that biofilm changes the roughness of PVC pipes which may further affect pipe longevity.

Traditional methods of microbial quantification for irrigation water using colony counts from agar culture require dedicated laboratory space and trained personnel, making them less suitable for on-site application by horticulture growers. Dehydrated Petrifilm™ culture plates are a simpler method than agar, but are still time-consuming and require 2-3 days to culture. Adenosine Triphosphate (ATP) tests may provide an easy and reliable method for quantifying microbes in water that is more rapid than culturing microbes. The objective was to compare ATP measurements against colony counts cultured using Petrifilm™ for assessing microbial water quality. Lake water was recirculated through an ozone system until a target oxidation reduction potential (ORP) of 700 mV was reached. Samples were collected at the following ORP intervals: control, 300 mV, 400 mV, 500 mV, 600 mV, and 700 mV. Samples were plated for aerobic bacterial counts and yeast and mold counts using Petrifilm™ culture plates. Samples were also analyzed for free and total ATP concentration using the Hygiena EnSURE luminometer and its accompanying free and total ATP swabs. Microbial ATP was calculated by subtracting free ATP from total ATP. Results showed a consistent decrease in bacterial and fungal counts with increasing ORP using Petrifilm™ culture plates. At 700 mV ORP, there was 99.5% reduction of bacterial colony counts and 92.8% reduction of fungal colony counts from the initial. Similarly, a decreasing trend was observed for free, total, and microbial ATP concentration with increased ORP levels. There was a 97.5 % reduction of microbial ATP from the initial concentration at 700 mV ORP. A positive correlation was observed between microbial ATP measured with the luminometer and bacterial counts obtained from Petrifilm™. Integrating ATP quantification into routine monitoring practices could provide easy and rapid results and enhance the efficacy of microbial assessments in irrigation water.

Nurseries and greenhouses in California face challenges of limited water supply and increased scrutiny from water quality regulators. Improving irrigation efficiency thus minimizing irrigation runoff are the main strategies to save water and comply with regulations. Evapotranspiration-based (ET) methods that make use of weather station data has the potential to substantially improve efficiency. In California, a statewide network maintained by DWR CIMIS project is widely used. However, crop-specific coefficients to calculate irrigation needs from weather data are not widely available in the nursery industry, particularly for large (15-gal and up) containers. In this project we measured water use and developed crop coefficient for 15-gal trees, one low water user (Olive, Olea europaea) and two high water users (Sycamore, Platanus acerifolia and Ficus microcarpa) with different canopy architectures. Container weight was measured with load cells (Omega LC103B, a weighing device similar to a scale), with values logged every minute by a Campbell Scientific data logger (CR1000X). Daily water use was calculated as the difference in weight from after each irrigation to before the following one. Local CIMIS reference ET was used to calculate crop coefficients. Tree water use yielded crop coefficients averaged 1.19 for Ficus; 0.57 for Olive and 1.21 in Sycamore during fall 2023 before defoliation started to occur for Sycamore in mid-October. Olive and Ficus defoliated through winter reaching the lowest crop coefficient in March 2024 when the coefficient was 0.42 for Ficus; 0.22 in Olive and 0.12 in Sycamore. Crop coefficients were substantially lower than those presented by Burger et al., 1987. for similar woody ornamentals grown in 1-gal containers. The difference is that Burger’s crop coefficients were calculated using the container surface area, while we used the (larger) block area divided by the number of containers. While less meaningful from a plant physiology point of view, a block-based crop coefficient is more useful for irrigation management and more similar to the crop coefficient calculation in field crops, grape vines and fruit trees. Results from our method can be converted to Burger et al. method by dividing by interception efficiency (i.e. cumulative container surface area divided by irrigation block area).

Container nurseries produce a high volume of operational water (OW) during irrigation and storm events. OW is irrigation return flow (IRF) and storm runoff that has traveled through crop production areas and could carry sediment and agrichemicals, making nurseries a potential contributor to nonpoint source pollution. OW is collected in retention reservoirs for treatment and reuse or allowed to leave the site. A monitoring program was conducted on five production areas (study catchments) with two different irrigation systems (i.e., overhead and spray stake) in two container nurseries located in the Midwestern USA (Central Lowland physiographic region). Total suspended solid (TSS), dissolved inorganic nitrogen (DIN) and phosphate (PO4-P) in OW during storm and irrigation events. We found median event mean concentrations (EMCs) during irrigation events for TSS, DIN, and PO4-P were 131 mg∙L-1, 2.9 mg∙ L-1, and 1.2 mg∙ L-1, respectively. During storm events, DIN and PO4-P EMCs were similar to irrigation events; however, TSS EMCs were almost 8 times greater than those of irrigation events. The median daily TSS, DIN and PO4-P load per ha during storm events were 13.3 kg·ha−1·day−1, 82.3 g·ha−1·day−1 and 43.5 g·ha−1·day−1, respectively, which were 20, 3, and 4 times greater than those of irrigation events. The results indicated that the portion contribution of storm and irrigation for producing TSS was 86% and 14%, respectively. The results of this study can facilitate improved irrigation scheduling and help assess potential treatment options.

Traditional irrigated landscapes and in particular turfgrass dominated landscapes are being challenged across the U.S. due in part to the demand on potable water supplies. So called “ornamental” turfgrass will be outlawed in Nevada by 2027 and efforts are underway in other areas of the desert southwestern states to do the same. Meanwhile, in these areas, aggressive turfgrass removal programs utilizing financial incentives are occurring. This dramatic change is due to water supply associated with the Colorado River and western water supply in general. In the eastern U.S. changes are occurring in new development in North Carolina warm season grasses are displacing cool season grasses in new landscapes. Accordingly the new trend is to install bermudagrass without irrigation. In Florida, numerous municipalities have or are adopting codes mandating a maximum of the landscaped area as 60% sprinkler irrigation, which means turfgrass, and in some municipalities as low as 20% of the landscaped area. The remainder of the landscaped area is filled with a mixture of microirrigated ornamentals, mulched area, or unirrigated turfgrass. Some newer developments are eliminating irrigated turfgrass altogether. The Florida-Friendly Landscaping (FFL) program is uniquely positioned to deliver education relevant to the radical change that is occurring in designed and built landscapes. Many local governments are adopting landscape codes that include or mandate FFL principles. This talk will discuss these trends along with the factors driving this cultural change of landscapes and in particular the use of turfgrass in landscapes. Additionally, the talk will focus on the challenges ahead for landscapes under water supply constraints and how they may impact nonpoint source pollution from urban areas.