ASHS 2025 Conference

A forum for discussion of potential collaborations with regards to plant growth and culture – i.e. propagation, root growth, water management, weed control, PGRs, plant nutrition, etc.

this study aimed to assess how irrigation water and seed magnetization affected the initial growth of okra, bell pepper, cucumber, lettuce, and eggplant seedlings. Five treatments and four replications were used for each species in the randomized block design (RBD) experiment. T1 was irrigation with tap water; T2 was neodymium magnetization of seeds plus irrigation with tap water; T3 was commercial magnetization of seeds plus irrigation with tap water; T4 was lack of seed magnetization plus irrigation with neodymium magnetized water; and T5 was lack of seed magnetization and irrigation with commercial magnetized water. We assessed the following: emergence speed index (ESI), average emergence time (AET), emergence percentage (E%), shoot dry matter (SDM), root dry matter (RDM), number of leaves (NL), root length (RL), stem diameter (SD), and plant height (PH). Normality and variance analysis were performed on the data, and the Tukey test was used to compare the means at a 5% probability level. The study's findings demonstrate the advantages of magnetically treated water for seedlings. Using water that has been magnetized by a neodymium magnetizer produced superior results for lettuce seedlings. The highest RL, NL, RDM, and ESI values were obtained for bell peppers when they were irrigated with water that had been magnetized by a neodymium magnetizer. The time it took for cucumber, eggplant, and okra seedlings to form was shortened by either magnetizing the seeds or watering them with tap water. Overall, the results of seed magnetism have been more noteworthy than those of irrigation water magnetization.

Agriculture continues to account for over 70% of global freshwater withdrawals, despite extensive research into water conservation methods in food production. A significant portion of this water usage is attributed to irrigation. In vegetable crops, the traditional raised bed system with plastic mulch can reduce irrigation application by minimizing evaporative losses. However, this system does not prevent water and nutrient losses to deep percolation or lateral movement outside the bed area. Therefore, this study evaluates an alternative raised bed system (H2grow), and compares its impact on water use, yield, and fruit quality in bell pepper production against the conventional raised bed system. Six treatments were tested, which included three nitrogen (N) application rates in both raised bed systems (bed type). A split-plot design was used, with bed type as the primary factor and nitrogen rates as the secondary factor. All treatments were replicated four times. Soil moisture sensors were used to trigger irrigation when soil moisture levels fall below 90% field capacity. Soil moisture, nutrient levels, and tissue nutrient content were monitored throughout the growing season. Yield and fruit quality (fruit wall thickness), were assessed at harvest. Preliminary results show that cumulative water use under the H2grow was 33% lower than the conventional raised bed, regardless of nitrogen application rates. This corresponds to a water savings of 1460 m³/ha. Although there were no significant differences in yield or wall thickness between bed types; the H2grow system showed promising potential over conventional beds with a p-value of 0.08 for yield and 0.06 for wall thickness. Nitrogen application rates had no significant effect on yield or fruit wall thickness, though fruit biomass was lowest under the low-N treatment. These findings demonstrate that the H2grow system significantly conserves water in bell pepper production and has the potential to reduce the water footprint in commercial vegetable production. As water conservation becomes an increasing concern in agriculture, this innovative technology offers a critical solution to address the growing challenge of freshwater use in food production.

Strawberry production in Florida traditionally relies on impact sprinklers for bare-root transplant establishment and freeze protection, leading to significant water consumption and potential nutrient leaching and runoff. This study assessed micro-sprinkler systems as alternatives to enhance water use efficiency while maintaining crop performance. The objectives were to (1) evaluate micro-sprinklers in research and commercial settings and (2) assess sprinkler distribution uniformity under different wind conditions. Field trials at the Plant Science Research and Education Unit in Citra, FL compared four micro-sprinklers to an impact sprinkler (control), measuring water use, plant vigor, and yield. The tested systems utilized Mini Revolver, SuperNet Jet, Mini-Wobbler, and Xcel Wobbler micro-sprinklers. The irrigation systems were arranged in a randomized complete block design with four replications. Additionally, lower quarter distribution uniformity (DUlq) tests with catch cans were conducted to evaluate sprinkler efficiency for freeze protection across varying wind conditions in Citra. The best-performing micro-sprinkler system was evaluated on a commercial strawberry farm in Plant City, FL in comparison with the grower’s Rotator sprinkler system. In Citra, all micro-sprinkler systems used less water than the impact sprinkler for bareroot transplant establishment and freeze protection. Water use was lowest with the Mini-Revolver, which decreased water use by 66% during establishment and 64% during freeze protection without adversely affecting plant survival or yields. Similar reductions were observed at the commercial farm, with water savings reaching 58% during establishment and 63% during freeze events. Significant variation in DUlq in response to wind conditions was observed among the sprinkler systems. Wind speeds >7 mph decreased DUlq, with the Mini-Revolver resulting in the lowest DUlq. However, at wind speeds 7 mph, which would decrease freeze protection effectiveness.

Deficit irrigation is an agricultural practice that can enhance crop water productivity (CWP) when yields are not affected, and be a technique to support crop production under persistent droughts and reduced agricultural water availability. Over two seasons, we evaluated grafted and ungrafted cantaloupe melon (Cucumis melo L.) under three consistent irrigation regimes: 100% of field capacity (FC; full irrigation), and 70% and 50% irrigation volumes of the full irrigation, resulting in moderate and severe deficit irrigation treatments, respectively. Although the deficit irrigation treatments accentuated drought stress through the season, plants in the moderate deficit irrigation (70% FC) maintained their plant water status and slightly lowered stomatal conductance (gs) and photosynthetic rate (Pn) when compared to full irrigation. Under severe deficit irrigation (50%), plants had lower water potential than the full irrigation, and a reduction of 65% in gs and 47% in Pn, when compared to the full irrigation. The yields of the 100% and 70% irrigation treatments were similar in one year and lower for the 70% FC in the second year. The severe deficit irrigation had on average a 40% lower yield than the full irrigation. Overall, the moderate deficit irrigation had a 25% reduction in applied water, and either a similar or a higher CWP, depending on year, when compared to the full irrigation. Melon grafting did not improve yield under deficit irrigation conditions; however, it increased yield under full irrigation and low environmental stress (i.e., year). This study shows that melons can acclimate to lower water availability and sustain yields under a constant, moderate deficit irrigation, which can be an alternative for growers that face long-season droughts and lower irrigation water allocation.

Sustainable management of irrigation water is critical for soilless greenhouse production systems, particularly in ornamental plant cultivation, where agrochemical (pesticides, nutrients, and growth regulators) use is intensive. Recycled irrigation water carries agrochemicals from production surfaces, containers, substrates, and system components. Even at low concentrations, these compounds can be phytotoxic to sensitive crops or pose environmental risks if discharged. While recirculating irrigation systems improve water efficiency, they require the use of treatment technologies to remediate agrochemicals. Woodchip bioreactors, commonly used for nitrate removal, have also shown promise in remediating phosphates and pesticides. They provide a carbon source and growth matrix for diverse microbial communities. Typical anaerobic conditions facilitate denitrification, and the biofilm further increases the reactive surface area where pesticides can interact with degrading enzymes to enhance pesticide remediation. Integrating aerobic bioreactors as a secondary stage can promote dissolved organic carbon release and enhance degradation of certain pesticides. Hydraulic retention time (HRT) is a key design factor, influencing nutrient retention and pesticide removal by controlling contact time with bioreactor microbiomes. Shorter HRTs support nutrient recycling for irrigation reuse, while longer HRTs enhance nutrient and pesticide degradation through extended microbial processing. We evaluated the performance of a sequential two-stage non-aerated (stage 1) - aerated (stage 2) bioreactor configuration in reducing effluent pesticide concentration and load under varying hydraulic retention times (HRTs). Two two-stage systems, each consisting of two bioreactors, were installed at a Michigan wholesale greenhouse, treating recirculating operational water from an 11,500 m² production area. These systems operated for 160 days at HRTs of 30 (30HRT) and 60 minutes (60HRT) per stage, corresponding to bioreactor volumes of 1,135 L and 2,271 L per stage, respectively. Preliminary results indicate that both 30HRT and 60HRT systems treated an average daily volume of 36,225±2,395 L. Average recycled Total Nitrogen load was 91% and 2.6 kg d-1 for 30HRT, and 78% and 2.3 kg d-1 for 60HRTs, respectively. Phosphate and pesticide content is currently being analyzed, with early observations showing phosphate load shifts from non-aerated to aerated conditions. These results will be presented at the conference.

Irrigation return water (IRW) from the nursery and greenhouse industries contains agrochemicals (pesticides, nutrients, and growth regulators) that pose significant phytotoxic and environmental risks within the operation and to the surrounding ecosystem. Agrochemicals can contribute to plant injury, eutrophication, groundwater contamination, and ecological toxicity. Woodchip bioreactors offer a cost-effective, sustainable solution for contaminant mitigation by supporting diverse microbial communities. Under anaerobic conditions, woodchip bioreactors facilitate nitrate reduction, while biofilms enhance pesticide degradation via enzymatic activity. Hydraulic retention time (HRT) regulates the duration of contaminant-microbiome interactions, balancing nutrient recycling in IRW at shorter HRTs and enhanced pesticide degradation at longer HRTs. However, newly established bioreactors typically experience a lag phase before reaching optimal contaminant removal efficiency due to the time required for microbial communities to develop. In this study, we investigated the potential of seeding new bioreactors with biofilms from established systems to accelerate this transition. Thirty-six woodchip bioreactors were evaluated under three HRTs (4, 14, and 24 hours) and three seeding levels (0%, 5%, and 10%) over 170 days. Simulated IRW containing nitrate, phosphate, and eight pesticides (acephate, atrazine, bifenthrin, chlorpyrifos, cyazofamid, oxyfluorfen, sulfoxaflor, and thiophanate-methyl) was used to assess performance. Preliminary results indicate that the 10% seeding at 4HRT yields the highest total nitrogen removal (6.2 g/day), compared to the 5% seeding at 4HRT (3.1 g/day) and the unseeded treatment at 4HRT (2.8 g/day). This suggests that a higher microbial load, combined with a shorter retention time, may be the most effective approach for removing Total Nitrogen.

In-situ resource utilization at the lunar surface has been proposed for food production during human exploration missions. However, lunar regolith’s sandy texture holds less plant-available water than most of Earth's fine-textured agricultural soils. Reduced gravity at the lunar surface limits drainage from containerized media, likely causing root-zone hypoxic stress without appropriate irrigation management. Sensor-based irrigation systems may mitigate these challenges by maintaining an optimal medium volumetric water content. Evaluating the palatability of crops is also crucial, though sensory evaluation is uncommonly included in crop production studies. Hence, this research aimed to quantify the effects of sensor- and time-based irrigation strategies on the development and growth of Lactuca sativa (lettuce) grown using two continuous harvesting techniques in a containerized Turface MVP medium, a coarse calcined clay aggregates. Lettuce seeds were sown in 48 containers filled with the Turface MVP (particle sizes 0.8-3.4 mm) premixed with 15N-3.9P-10K controlled release fertilizer. Additionally, 24 containerized media were left unseeded to serve as controls. The containerized media were randomly assigned to sensor- and time-based irrigation under “pick-and-eat” and “cut-and-sow” harvesting techniques. Sensor-based irrigation maintained volumetric water content at 0.40 m3·m-3 through frequent sensor scanning and automated irrigation when sensor readings fell below the setpoints, while the media at time-based irrigation management were irrigated to saturation once per day. Under the “pick-and-eat” method, sensor-based irrigation increased the leaf fresh and dry weights, and photosynthesis rate by 81%, 39%, 61%, respectively, compared with plants under time-based irrigation at the end of experiment. The “cut-and-sow” method resulted in lower leaf fresh and dry weights than the “pick-and-eat” under both irrigation treatments. However, sensor-based irrigation led to increases in the medium’s electrical conductivity, causing plants under salinity stress because the phosphorus, potassium, and magnesium concentrations in the leaf tissue increased compared with those under time-based irrigation. Sensor-based irrigation improved overall acceptability of samples under “pick-and-eat” in sensory testing, with 50% of respondents disliking the time-based samples. However, the "cut-and-sow" samples under time-based irrigation exhibited higher overall acceptability, though 75% or more testers liked both samples. Sensor-based irrigation improved the yield of lettuce under "pick-and-eat" method but caused salinity stress. Conversely, the "cut-and-sow" method led to lower yield, but improved plant palatability under time-based irrigation. Nevertheless, with higher yield, increased mineral content, and improved consumer acceptability, the “pick-and-eat” method under sensor-based irrigation demonstrates potential for sustaining continuous crop production.