ASHS 2025 Conference

The development of genotypes resilient to abiotic stresses like drought has a pivotal role over the impacts of climate extremes on global food security. Recent studies suggest that modulating the activity of polyamine oxidases (PAOs) in crop species could enhance stress tolerance. Given the limited data on how altered PAOs expression (either overexpression or silencing) affects physiological and anatomical traits that may contribute to plant resilience, the aim of the present study is to investigate phenotypic variability - focusing on leaf structure and function - in tomato genotypes with modified polyamine metabolism under deficient irrigation. Three tomato genotypes were cultivated in a greenhouse, one reference (cv. Moneymaker) and two transgenic lines of the reference genotype with silenced expression of the genes encoding the homologous enzymes SlPAO3 and SlPAO4 of PAO. Two irrigation regimes were applied: Control (100% field capacity, FC) and Drought (20% FC). Following the development of new leaves under drought conditions (long-term acclimation), anatomical features of the leaves and petioles, as well as gas exchange parameters, were assessed. Results showed that, regardless of genotype, water deficit led to a reduction in leaf area, reflecting a decrease in transpiring surface, an adaptation of leaf function under limited water availability. The slpao3 plants, regardless of the irrigation regime, exhibited a smaller total vascular tissue area per petiole cross-section compared to both the reference genotype and the slpao4 plants. However, during acclimation to drought stress, an increase in vascular tissue area was observed only in the slpao3 plants. These findings align with previous studies highlighting the involvement of polyamines in xylem differentiation processes. Long-term acclimation resulted in a reduction in xylem vessel size and an increase in vessel density, irrespective of genotype, indicating an adjustment of hydraulic traits to meet the water demands of acclimated leaves. Petiole vascular characteristics, leaf area, and gas exchange parameters, independent of genotype and treatment, showed strong correlations among them. These results confirm a coordination presence between hydraulic function and photosynthetic response. Further research is needed to clarify how this coordination influences water transport and use efficiency, and to explore whether modulation of PAOs activity could serve as an effective strategy to enhance plant resilience to environmental stresses.

Short-day onions are grown for fresh market in the southern region of the US, and they require around 10 to 12 hours of photoperiod or 12 to 14 hours of nighttime to thrive. These onions tend to produce fewer, thinner layers and have higher moisture contents, making them susceptible to bruising. When short-day onions are harvested by machines, a small percentage of them are damaged and the rest experience bruising during the harvesting process. This leads to a focus on bulb firmness and how it can affect the reduction of bruise damage. The current study seeks to identify bulb characteristics that affect bulb firmness and their relation to the overall bruise damage in short-day onions. For this, early and main season maturity varieties were used and several bulb characteristics including bulb weight (gm), height (cm), width (cm), number of rings, firmness, growing point (single versus multiple centers), and total soluble solids (°Brix) were measured. Correlation among bulb traits was analyzed using correlation in R corrr package. In the early season, there was correlation between bulb weight and bulb width (r=0.920343), firmness and single center (r=0.504853), and single center and ring number (r=0.609349). There was no significant correlation between bulb firmness and the remaining bulb traits. A negative correlation was observed between firmness and moisture content (r=- 0.412323) and firmness and ring number (r=- 0.5084) in the main maturity season trial, but not enough to significantly impact the bulb firmness. The results suggested that in early maturity bulbs, a single center directly correlated with firmer bulbs, but in the main maturity season, firmness had a negative correlation with moisture content and ring number. Results will be validated with the second season trial during the 2024-2025 season.

Orange-fleshed sweetpotato (Ipomoea batatas) cultivars with moist, sweet texture are the most popular type of sweetpotatoes grown in the United States, while elsewhere in the world, white, yellow, and purple-fleshed types with firm, dry texture are more popular. There is a market opportunity in the United States for diverse sweetpotato cultivars, however, their yield tends to be low as they have not received the same breeding attention as orange-fleshed cultivars. In this experiment, six advanced breeding lines from the USDA, representing a diversity of flesh colors, textures, sweetness, and firmness, were compared to cvs. Covington (standard) and Cascade (new release). The experiment was carried out in a certified organic field in Mount Vernon, WA in 2024 and is being repeated in 2025. Each plot included 15 plants with 4 replicate blocks. In 2024, sweetpotatoes were planted on 4 June in raised beds covered with black polyethylene mulch and with drip irrigation. Harvest was by hand on 7 Oct., roots were sorted by size, and damage by wireworms (Agriotes lineatus, A. obscurus, Limonius canus), the most significant insect pest impacting sweetpotatoes in this region, was assessed using the WDS severity index ( 0 = no scars, 1 = 1-5 scars, 2 = 6-10 scars, 4 = >10 scars). Without accounting for wireworm damage, yield (US No. 1 and US No. 2) of ‘Covington’ (orange, soft flesh) was highest (18.2 t/ha) followed by USDA-22-009 (13.8 t/ha, yellow flesh), and ‘Cascade’ (white, firm flesh) had low yield (6.7 t/ha) followed by purple-fleshed breeding lines USDA-17-090 (4.1 t/ha) and USDA-16-051 (3.1 t/ha). Orange-fleshed breeding lines USDA-16-031 (3.8 t/ha) and USDA-19-036 (1.7 t/ha) and yellow-fleshed USDA-23-039 (0.5 t/ha) all had low yield. ‘Cascade’ was the most wireworm resistant (WDS severity index 1.61) followed by USDA-16-051 (2.33), while ‘Covington’ and USDA-22-009 were the most susceptible (3.67 and 3.54, respectively). The breeding lines USDA-16-031, USDA-17-090, USDA-19-036, and USDA-23-039 had similar ratings, ranging from 2.83 to 3.39. While yields of ‘Cascade’ (white, firm flesh) and USDA-16-051 (purple flesh) were less than ‘Covington’, farmers may be interested in growing these niche cultivars for their wireworm resistance and to cater to consumer interests.

Garlic (Allium sativum) is a cool season and flavorful vegetable crop that has a long history in culinary, horticultural, medicinal uses. Oklahoma is a state characterized by diverse weather and soil types, but there is an economic opportunity for garlic production with optimal planting techniques and planting recommended cultivars. The number of farmers producing garlic increased from 28 to 44 between 2017 and 2022. This trial was conducted at the Cimarron Valley Research Station with Oklahoma State University in Perkins, Oklahoma and evaluated ten cultivars grown using drip tape irrigation, no mulch, and a no-spray approach to weed and pest control. Total graded marketable yield and allicin content were recorded during the 2023-2024 and 2024-2025 growing season for softneck and hardneck cultivars including: ‘California Early’, ‘Chesnock Red’, ‘Duganski’, ‘German Extra Hardy’, ‘German White Stiffneck’, ‘Inchellium Red’, ‘Music’, ‘Purple Glazer’, ‘Romanian Red’, and ’Sicilian Artichoke.’ In 2024, the top performing cultivars were ‘German Extra Hardy’ and ‘Inchellium Red’. These were significantly higher yields that ‘Duganski’. No other statistical differences were observed. Their respective marketable yields were 2,704 and 2,538 pounds per acre. In addition, we recorded allicin content for each cultivar using a spectrophometric assay. Allicin is one of the most important thiosulfates in garlic and its presence adds market value for those interested in the nutritional and health benefits of garlic. We observed statistically significant differences among the cultivar entries. ‘California Early’ and ‘Duganski’ had a significantly higher allicin content at .66 grams and .59 grams per 100 g sample than ‘German White Stiffneck’ at .49 grams per 100 g sample. Additional research of allicin content among different cultivars of garlic is needed to guide consumers and healthcare professionals in selecting the best cultivar for fresh market consumption.

Broccoli, scientifically known as Brassica oleracea var. italica, was first cultivated in the 17th century. Based on 2022 USDA Ag census, in the United States, broccoli is grown on 96,600 acreage. Broccoli is damaged by more than 25 insect pests. Some pests are region/place specific and some are common across the world like aphids, mites, etc., Pests like imported cabbage worms, cabbage loopers, and diamondback moths have a destructive effect on the crop in different growth stages of the crop. Organic pesticides to manage these pests have mixed results and account for increased labor and costs. Mesotunnels could serve as a viable pest management approach within organic production systems. “Meso” means “middle,” so mesotunnels are medium-size tunnels – taller than low tunnels and shorter than high tunnels. A breathable nylonmesh fabric (brand names include ProtekNet and ExcludeNet) that resembles window screen are placed over the mesotunnel. The fabric acts as a barrier for insect pests and prevents their entry and disease-carrying pathogens. These nylon nets are breathable, durable, and light permissible which can also protect from extreme weather conditions like hail damage. This study includes the following three treatments: 1) Mesotunnel with proteknet, 2) Organic insecticides, and 3) Control (no mesotunnel or organic insecticides). Mesotunnel treatment resulted in less pest damage (No.of holes/plant) with a mean 14 when compared to organic insecticides which had mean damage of 22. A significant difference was observed in pest damage between the treatments. Regarding marketable yield, the highest was observed in the Mesotunnel treatment. However, no significant difference was found between the treatments. This study aims to identify the most effective method of pest management in broccoli production while minimizing the environmental impact through reduced reliance on pesticides. Keywords: mesotunnels, proteknet, excludenet, organic pesticides

Matching breeding target with consumer preference is the goal of many crop production methods. But this is normally a difficult challenge when the selected disease- and pest-resistant materials do not meet the consumers’ product preference. In this report, we highlight the efforts we are making to deliver cucumber lines with consumer-preferred visual traits and that have combined resistance to melonworm, leaf miner, aphids, and Downy mildew. After a series screening of 100 lines from the USDA, 36 showed at least 40% resistance to leafminer and melonworm in 2022 and 2023. Of these, we have evaluated 16 against lines with varying degrees of resistance and six susceptible lines against three commercial varieties commonly grown in the Virgin Islands. All the 25 cucumber lines were exposed to open natural infestation by leaf miner, melonworm, aphids and downy mildew in the open field and scored for resistance based on visual ratings designed for each infestation. We used a mathematical model that considered multiyear and multilocation performances to rank the lines for combined resistances. Unfortunately, the top three resistant lines were not among the top five visually appealing fruit types on a consumer preference scale based on a survey of 245 respondents. We report on the prospects and anticipated timeline for the development of cucumber plants with the preferred fruit type and disease and pest resistance traits. Our study has the potential to deliver cucumber varieties that are highly adapted to the Caribbean abiotic and biotic stresses and that have significantly reduced pesticide footprints. Key words: Consumer preference, cucumber, pest resistance, screening, trait

A greenhouse culture system simulated in-ground curing by imposing pre-harvest water deprivation treatments in sweetpotato. Virus-tested sweetpotato cv ‘Beauregard’ cuttings were planted at the following staggered times relative to the control (0d): 10 days (10d) and five days (5d) earlier, respectively. Water deprivation treatments were applied 10d and 5d pre-harvest. The first study terminated experiments when the control plants attained 30 days of growth. Storage root sections 1-2 mm thick were obtained from the broadest part of the storage root, stained with phloroglucinol, followed by image capture with a microscope. Digital image analysis was performed by measuring the area of the continuous lignified zone (CLZ) below the phellogen layer and calculating % CLZ after measuring the total area of the cross-section. Simulated WD at 10d and 5d was associated with a six- and three-fold increase in % CLZ, respectively. None of the control SRs showed 100% CLZ, while 50% of SRs subjected to 10d WD showed an intact ring of lignified tissue below the phellogen layer. Storage roots from control plants consistently showed breaks in the phellem tissue relative to SRs subjected to WD treatments. In the second study, plants were grown for up to 50 days, and harvested SRs were kept in ambient conditions for weight loss measurements. Water deprivation was associated with reduced weight loss in SRs relative to SRs grown in well-watered conditions. These findings can lead to follow-up work to validate increased skin durability with pre-harvest, in-ground curing in production areas where postharvest curing facilities aren’t available.

Sweetpotato (Ipomoea batatas) is a tuberous root crop and an important agricultural staple in the U.S. Virgin Islands. Due to its year-round production potential, drought tolerance, adaptability to calcareous soils, and cultural significance, a more efficient land-use and cropping system is needed. The objective of this study was to investigate the impact of sweetpotato cutting length on yield per linear foot on five cultivars, ‘Bonita’, ‘Bellevue’, ‘GA-11’, ‘Murasaki’ and ‘Sakura-40’. Actively growing vines from five cultivars were propagated using 6–8-inch terminal cuttings and 3-foot cuttings. An 8-inch drip irrigation system was used for both treatments. After 130 days, harvest data were collected on number of tuberous roots, weight, and marketable yield. Results showed that Bonita, Bellevue, and Murasaki produced higher yields (kg/ft) when planted with 6–8-inch cuttings, whereas ‘GA-11’ and ‘Sakura-40’ yielded more with 3-foot cuttings. Similarly, ‘Sakura-40’, ‘Bonita’, and ‘Bellevue’ had greater numbers of marketable and total roots per foot with 6–8-inch cuttings, while ‘Murasaki’ and ‘GA-11’ performed better in both categories with 3-foot cuttings. These findings indicate that optimal cutting length is variety-specific, with certain cultivars favoring shorter cuttings for higher yield and root number, while others benefit from longer cuttings. This research was funded by a USDA Mutistate Hatch Grant.

In the northeastern US, cold-tolerant crops such as spinach are an important source of winter income for high tunnel growers. Supplemental rowcovers are used on crops inside unheated high tunnels to expose plants to optimal temperature ranges for longer periods of each day and to provide greater protection from injurious low temperatures. Rowcover management impacts temperature, light availability, humidity, pest populations, crop yield, and labor requiremenst. Some growers actively manage rowcovers, removing them daily to optimize light exposure and then reapplying them in the evening and on cloudy or very cold days. This is thought to provide a yield benefit due to increased crop light availability, but it is labor intensive and experienced growers often make decisions about removal based on a combination of current conditions and forecasted weather. Therefore, some growers opt for a “set it and forget it” approach, where layers are applied once and then only removed as needed, rather than daily. Here we describe the tradeoffs of “active” rowcover management, where rowcovers are removed during the day and replaced nightly, compared to “passive” management, where rowcover is removed only for harvest and regular maintenance. We conducted a replicated trial in two experimental years in an unheated high tunnel to investigate the effects of rowcover management on winter spinach yield, pest abundance, and abiotic environmental factors including growing degree hour accumulation. We also compared our observations with those from commercial tunnels managed by three experienced growers in the northeast. In both experimental years, growing-degree hour accumulation and the cumulative amount of time below freezing did not differ significantly between active and passive management. However, active rowcover management did result in greater light accumulation, lower relative humidity, and increased spinach yields in one experimental year compared with passive management.

Seagrass that washes ashore is an abundant, traditional amendment for crop production on Yap Islands, yet its potential for modern sweetpotato (Ipomoea batatas) cultivation remains largely unexplored. Traditionally, semi-decomposed seagrass is incorporated to create raised beds where sweetpotato is grown for several years. While compost and manure can be effective amendments to improve the conditions of the highly weathered, acidic volcanic soils of the Yap Islands, they are costly, labor intensive, and in short supply. By utilizing an abundant, free resource, this project seeks to improve crop yields and extend the productive life of agricultural lands. This study includes two field experiments that compare semi-decomposed seagrass with conventional commercial fertilizer for two sweetpotato cultivars in two production systems, raised-beds and grow-bags. Experiment 1 utilizes raised beds established on three farm sites with an improved sweetpotato cultivar, where treatments include medium and high application rates (by weight, approximately 40 and 60 kg N ha-1, respectively) of semi-decomposed seagrass and a control treatment using commercial fertilizer (10N-20P-20K) at N rate equivalent to the medium seagrass application. Each treatment is randomized in a complete block design, with six replicates per treatment. Experiment 2 is a split-plot design and compares a traditional vining and a modern sweetpotato cultivar (main plot treatment) in container cultivation using 10-gallon grow bags filled with a soil mix amended with seagrass at medium and high ratios compared to a commercial fertilizer control at N rate equivalent to the medium seagrass application (split-plot treatment). For both experiments, the seagrass is collected, washed, and piled to reduce salinity to acceptable thresholds, with leachate EC measured weekly. Seagrass is then shredded and piled to accelerate decomposition. Analysis results of semi-decomposed seaweed are 15% dry weight with 1.8% N on average, and application rates are 21 g and 32 g per sq foot of soil for N application rates of 40 and 60 kg.ha-1, respectively. Community buy-in and trust building are being achieved through collaboration with island-based agricultural educators and meetings with traditional leaders. This research has the potential to enhance sweet potato production on the Yap Islands, improve resource management, and provide an affordable soil amendment option for local farmers. The project promotes environmental stewardship and contributes to cleaner shorelines and sustainable agricultural practices. The findings will offer critical insights for local agricultural educators and policymakers in optimizing land use and advancing low-cost, high-yield cultivation methods in resource-limited settings.

Phosphorus (P) is an essential nutrient for snap bean growth, directly influencing root development, plant health, and overall yield. However, P bioavailability is often limited by soil fixation, particularly in highly acidic and alkaline environments. In the Hastings region, soil pH can drop to 4.7 during the growing season, leading to substantial P immobilization due to high concentrations of extractable aluminum (1,300–2,000 lbs/acre) and iron (250–600 lbs/acre). These metals readily react with P, forming insoluble complexes that restrict plant uptake. Chemically, one pound of aluminum can fix up to 2.6 pounds of phosphorus pentoxide, significantly reducing P availability for crop growth. Conversely, in the Homestead region, where soil pH reaches 8.4, P fixation occurs primarily through reactions with calcium, with one pound of calcium binding approximately 1.2 pounds of phosphorus pentoxide, further limiting P solubility. Conventional P fertilization typically relies on a single pre-plant application, which does not align with the plant’s continuous nutrient demands throughout the growing season. Moreover, prolonged soil-P interaction exacerbates fixation losses, further reducing bioavailable P. This study investigates the effectiveness of split P applications as a strategy to mitigate fixation and improve nutrient uptake efficiency. By minimizing phosphorus’s contact time with reactive metals, split applications—through multiple dry granular P applications or fertigation—help sustain adequate P concentrations in plant tissue. Preliminary results indicate that split applications significantly enhance P uptake and use efficiency, leading to higher snap bean yields compared to conventional single-dose treatments. These findings suggest that split P applications offer a more effective and sustainable approach to optimizing phosphorus management in snap bean and other vegetable production.

Biostimulants are gaining popularity as a tool for enhancing plant growth, mitigating abiotic stress, and improving crop yield and quality. Defined as substances or microorganisms that stimulate natural plant processes. Although skepticism about their efficacy initially limited their use, a growing body of research evidence demonstrates their positive effects on crop systems under both controlled environments and field conditions. However, the continuous development of new biostimulant formulations reinforces the need for further validation under commercial agricultural conditions. This study evaluates the effects of eight commercial biostimulant protocols, each with different composition and modes of action on tomato (Solanum lycopersicum) growth, fruit quality, and yield. The objectives are to: 1) quantify the effects on plant growth with parameters such as plant height, stem diameter and leaf chlorophyll content) 2) assess the impact on yield and fruit quality at harvest. The experiment followed a randomized complete block design with three replicates, each comprising eight treatments. Each plot contained 25 tomato plants, and data were collected from 10 selected plants per plot. Biostimulants were applied weekly or biweekly, via drench or foliar spray, according to the manufacturer’s instructions. Growth parameters were measured throughout the experiment, while yield and quality assessments were at harvest and during postharvest storage. According to the analysis of variance, plant height was significantly affected by protocol. Protocol 5 was statistically superior to the control in two of the three replicates followed by protocol 8 with one statistical significance in the three replicates compared to the control. There was not any statistical difference in diameter of treated plants compared to the control, however plants treated with protocol 8 had the greatest diameter in two of the three replicates. For the chlorophyll content, treatment 1 was the only one that showed a significant increase compared to the control. In terms of color, protocol 2 and 5 significantly increased fruit brightness while protocol 5 and 7 enhanced color saturation and protocol 1 altered hue compared to the control. The firmness of fruits at harvest was 2.08 to 2.85 kg without any significant differences within the protocol. In yield, protocol 5 was statistical significance in marketable weight, number 8 was statistical significance in count and weight in unmarketable category. According to the above, there is a significant benefit of specific biostimulants as treatments 5 and 8 in promoting tomato plant growth and improving certain fruit quality parameters. Key words: Biostimulants, protocol, plant growth.

Current vegetable production faces the challenge of productivity with growing demand for environmentally sustainable crop management practices. Biostimulants present a promising and sustainable strategy for mitigating the adverse effects of unpredictable weather patterns on vegetable crops, thereby enhancing resilience to heat stress, water deficits, and various biotic and abiotic stresses. While biostimulants have shown promising effects in various agricultural applications, there is limited literature on biostimulants and their role in regulating plant growth and development under conventional open field production systems. Additionally, there remains a research gap concerning the optimal application methods and rates of various biostimulants across different vegetable crops. Hence, this study analyzed the effectiveness of two different biostimulants seaweed extract and humic acid on mustard greens (Brassica juncea) performance using conventional farming methods in open field conditions. The biostimulants were applied through both soil and foliar application at two different rates to evaluate their effects on the growth, yield, and nutritional quality of mustard greens. Data was collected on various parameters, including the number of leaves per week, fresh and dry weight at harvest, nutrient content including chlorophylls, carotenoids, and mineral nutrient composition. Yield and nutrient compositions were improved by the application of seaweed at high concentration. In conclusion, seaweed application can be beneficial to improve mustard greens production in open field conditions.

Biostimulants have the potential to enhance plant growth and improve resilience to environmental stresses such as drought. This study investigated the effects of biostimulant application on the growth and physiological responses of two lettuce cultivars, ‘Green Oakleaf’ and ‘Red Oakleaf’, grown in a greenhouse at Mississippi State University. Plants were grown in containers under three substrate field capacities (40%, 70%, and 100%) and treated with one of four biostimulant treatments: Tribus®, Huma Pro®16, Kelpak®, or an untreated control. Data collected included plant growth index (PGI), leaf SPAD readings, photosynthetic activity, fresh and dry weights, and leaf color. Water availability and cultivar significantly affected PGI, biomass accumulation, and SPAD readings. The 70% and 100% field capacities resulted in the highest fresh and dry weights, while ‘Red Oakleaf’ exhibited greater dry weight and SPAD values than ‘Green Oakleaf’. Biostimulant treatments had no significant effect on any of the measured parameters. These results indicate that water availability plays a critical role in greenhouse lettuce growth, while the biostimulants tested did not enhance plant performance under the conditions of this study.

With increasing focus and shift towards soil health, sustainable soil management practices stand as critical approach to enhance the crop productivity and quality while improving production system as a whole. One method to improve soil health is through addition of soil amendments such as compost, animal manure and crop residues. However, there is limited literature on emerging organic amendments like biochar, vermicompost and peatmoss and their role in crop production in field-based conditions. Specifically, biochar has high cation exchange capacity and improves soil homeostasis, while vermicompost has more readily available nutrients. Several researchers have found synergistic effects when biochar and vermicompost were used in combination with high nutrient retention and uptake, supported by high activity of soil microorganisms. Similarly, peat moss is rich in organic matter and has high water absorption capacity. Although its use in soilless substrates has been widely explored, peat moss as soil amendment in open fields has limited literature. Hence, the current study investigated the role of organic soil amendments on yield attributes and nutritional profile of a leafy green vegetable, collard greens. Furthermore, soil parameters like organic matter content, soil nutrients and soil bulk density were observed before and after the crop period. Two open field trials were conducted in spring and fall under at Students Farm, Oklahoma State University, following certified naturally grown production practices. The soil amendment treatments were arranged in randomized complete block design within four blocks. Collard greens’ phytochemicals such as chlorophylls, carotenoids, flavonoids, phenols, and sugars were analyzed after harvest. Results show that vermicompost facilitated better crop performance by improving soil physical and chemical properties. The findings of this study provides sustainable horticulture practices by providing more information on added amendments and their role in improving soil health and enhancing crop quality, offering actionable insights for soil health focused production systems.

Nitrogen (N) is the macronutrient required in the largest amount by strawberry plants (Fragaria ×ananassa Duch.) and is often the primary factor limiting their yield. Florida’s sandy soils are highly prone to leaching of mobile nutrients like nitrate. Optimizing N fertilization is essential not only for maximizing economic returns but also for reducing the risks of environmental pollution caused by nitrate leaching and runoff. This study aimed to determine the growth stage-specific optimum N rates for the winter strawberry production system in Florida. Three field experiments were conducted in west-central Florida, each following a factorial design with four cultivars [‘Florida Brilliance’ (Brilliance), Florida MedallionTM 'FL 16.30-128' (Medallion), Florida PearlTM ‘FL 16.78-109’ (Pearl 109), and Florida Pearl® ‘FL 18.52-66’ (Pearl 66)] and five N rates (0, 0.56, 1.12, 2.24, and 3.36 kg/ha/d). Different N rates were applied during Weeks 3–8 (early growth) in Expt. 1, Weeks 9–14 (mid-growth) in Expt. 2, and Weeks 15–20 (late growth) in Expt. 3, with a baseline rate of 1.12 kg/ha/d before or after the treatment period. All experiments concluded at the end of Week 20, with total N application rates ranging from 94 to 235 kg/ha. Model fitting analysis was conducted to explain the yield response for N rates. In Experiment 1, marketable yield was fitted to linear models (r2=0.82−0.98) as a response to N rate, with slopes of 0.45, 0.45, 0.36, and 0.35 for Brilliance, Medallion, Pearl109, and Pearl66, respectively. Increasing the N rate from 1.12 to 3.36 boosted total marketable yield by 128%, 132%, 129%, and 126% for Brilliance, Medallion, Pearl109, and Pearl66, respectively, by the season's end. In Experiment 2, marketable yield of Medallion and Pearl66 followed linear models (r2=0.9−0.96) with slopes of 0.44 and 0.26, respectively, while other cultivars showed no significant slope differences. Increasing the N rate from 1.12 to 3.36 enhanced marketable yield by 137% for Medallion and 111% for Pearl66. In Experiment 3, no significant pattern was observed between N rates and marketable yield during the treatment period, but increasing the N rate slightly increased marketable yield at season's end for Brilliance (101%), Pearl109 (113%), and Pearl66 (104%), while negatively impacting Medallion (91%). Across all experiments, unmarketable yield, small fruit number, and soluble sugar content were not significantly (p

Nitrogen (N) is often the primary limiting factor in strawberry (Fragaria ×ananassa Duch.) production. Optimizing N fertilization is crucial for maximizing economic returns while minimizing environmental pollution risks. This study aimed to determine cultivar- and growth stage-specific optimum N rates for winter strawberry production in a subtropical sandy soil. Three field experiments (Expt. 1, 2, and 3) were conducted in west-central Florida, with four cultivars [‘Florida Brilliance’ (Brilliance), Florida MedallionTM (Medallion), Florida PearlTM (Pearl 109), and Florida Pearl® (Pearl 66)] and five N rates (0, 0.56, 1.12, 2.24, and 3.36 kg·ha–1·d–1). Different N rates were applied during Weeks 3–8 (early growth) in Expt. 1, Weeks 9–14 (mid-growth) in Expt. 2, and Weeks 15–20 (late growth) in Expt. 3, with a baseline rate of 1.12 kg·ha–1·d–1 outside the treatment period. All experiments concluded at the end of Week 20, with total N application rates ranging from 94 to 235 kg·ha–1. Model fitting revealed cultivar- and growth stage-specific yield responses to N rates. In Expt. 1, the best-fit models were linear for Brilliance, Medallion, and Pearl 109, with maximum yield increases of 102%, 109%, and 71%, respectively. For Pearl 66, the best-fit model was quadratic, with a maximum yield increase of 126% at 3.34 kg·ha–1·d–1. In Expt. 2, Medallion maintained a linear response with a maximum yield increase of 90%, whereas Brilliance followed a quadratic model, with a maximum yield increase of 70% at 2.27 kg·ha–1·d–1. Pearl 109 and Pearl 66 followed exponential plateau models, reaching 90% of their respective maximum yields with 89% and 73% increases at 1.64 and 2.09 kg·ha–1·d–1, respectively. In Expt. 3, no cultivar exhibited a significant model fit. Agronomic N use efficiency (ANUE, kg yield increase per kg N applied) showed contrasting results. In Expt. 1, only Pearl 109 exhibited a significant model fit, with a linear reduction of up to 30%. In Expt. 2, Medallion showed no significant model fit, whereas the other three cultivars reduced ANUE linearly by 27% to 38%. In Expt. 3, all cultivars followed exponential decay models, with maximum reductions of 57% to 63%. These results suggest that Medallion is the most responsive to N fertilization, while Pearl 109 is the least. Moreover, N fertilization efficiency could be improved by increasing its distribution during the early and mid-season growth stages and limiting late-season inputs.

Increasing salt stress and water scarcity necessitate research on plant salinity tolerance. This study investigated the effects of biochar crossandra (Crossandra infundibuliformis) under saline conditions. Three biochar rates (0%, 15%, 25%) were incorporated into commercial substrates, with salinity treatments of control, medium, and high at 0.2 dS∙m-1, 2 dS∙m-1, and 4 dS∙m⁻¹ respectively. Growth parameters (growth index, chlorophyll content, number of flowers), biomass, and physiological responses (photosynthesis, transpiration, stomatal conductance rate) were evaluated over time. The results showed crossandra tolerated salinity up to 4 dS∙m⁻¹ with minimal effects on flower production, biomass, and physiological responses, though growth index and SPAD values declined. At 2 dS∙m⁻¹, 15% biochar improved growth index, SPAD, number of flowers, biomass, and physiological rates comparable to controls. These results suggest biochar can mitigate salinity effects for crossandra plants.