ASHS 2025 Conference

Transplants provide an early start and help with better establishment and enhanced yield and quality in vegetable crops. For production of healthy and high-quality transplants, nutrient management is critical. There are several organic amendments available that can be directly added to the transplant growing media to provide essential nutrients for transplant growth and development. Some of the commonly used amendments include blood meal, bone meal, feather meal, fish emulsion, alfalfa meal, crab meal, shrimp meal, bat guano, etc., These organic amendments are obtained from dried animal blood or bone products which are rich in nutrients like Nitrogen, Phosphorus, and Potassium. Even though these amendments are available, there is lack of information on their efficacy and impact in organic transplant production. This greenhouse study conducted at Iowa State University, investigated the use of several amendments in broccoli transplant production. Treatments included: blood meal, bone meal, feather meal, fish emulsion, compost, conventional fertilizer, compost, and a no-fertilizer control. Plant height, stem diameter, SPAD (Soil Plant Analysis Development), dry biomass, and root length are the parameters we analyzed to determine the transplant growth. The findings show that the conventional fertilizer treatment had the tallest plant, with a mean height of 8.54 cm, followed by the blood meal with a height of 8.15 cm. No significant difference was observed between the conventional fertilizer and blood meal treatment. The highest mean stem diameter was found in the blood meal treatment, measuring 4.2 mm, followed by the feather meal treatment, which had a mean stem diameter of 3.65 mm. Blood meal and feather meal treatments were significantly different from each other. The plant biomass was high in the blood meal treatment at 3.36g. The blood and feather meal treatments differed significantly from the bone meal, compost, fish emulsion, and control treatments. Results from this study show that organic amendments can be successfully used to improve the transplant growth with a single application, potentially saving labor and cost. Keywords: transplants, organic amendments, SPAD, nutrients, blood meal, bone meal, feather meal.

Shifts in regional precipitation patterns and rising temperatures due to climate change have increased uncertainty surrounding optimal planting windows and nitrogen (N) management strategies for broccoli production in North Carolina (NC). In particular, growers face challenges in aligning planting schedules with ideal environmental conditions and adjusting N application rates to match crop demands under variable temperature regimes. Given that both air and soil temperatures directly influence crop nutrient uptake and development, this study aimed to evaluate the combined effects of planting date, nitrogen rate, and application timing on the growth and productivity of two commercially important broccoli cultivars: 'Eastern Crown' and 'Emerald Crown.' Field experiments were conducted at the Horticultural Crops Research Station of North Carolina State University in Clinton, NC. The first trial included four planting dates—early March, late March, early April, and late April—combined with three fertigation N rates of 120, 100, and 80 lb/acre. The second trial focused on two planting dates, late March and late April, combined with four pre-plant N application rates: 0%, 20%, 40%, and 60% of total recommended N. Across both trials, plant performance was assessed through measurements of canopy volume, aboveground biomass, leaf greenness via Normalized Difference Vegetation Index (NDVI), tissue nutrient content, and marketable yield. Results show that early planting dates were associated with lower accumulation of Growing Degree Days (GDD), which may have limited early crop development. In contrast, later planting dates generally experienced higher GDD accumulation, improving crop rate of growth. Higher N application rates were positively correlated with increased NDVI values, biomass, and yield. Reduced NDVI readings under lower N rates indicate a possible decline in plant vigor and photosynthetic activity. Additionally, strategic pre-plant N applications showed potential benefits in improving early plant establishment and nutrient status, particularly under later planting dates. Overall, our findings show the importance of optimizing both planting timing and N management strategies to improve broccoli productivity in NC. Tailoring N rates based on planting date and anticipated thermal conditions may contribute to more resilient production systems under changing climate conditions.

SafeRock micronized is a 100% natural mineral soil enhancer and fertilizer booster mined from unique sandstone deposits in United Kingdom and contains a balanced blend of over 70 nutrients and clay minerals. A field experiment was conducted at Blackville SC to evaluate the ability of SafeRock micronized to improve nutrient use efficiency, growth and yield of tomato and sweet corn. The experiment comprised of seven treatments [normal farming practices (NFP), NFP SafeRock soil mix (50 and 75 kg/ha.), NFP SafeRock fertigation (50 and 75 kg/ha.), 80% N

Ensuring nitrogen applications targeting the optimum rate is critical in tomato production. This is because nitrogen (N) requirements in tomato production may vary depending on the soil type, location, climate, and cultivation practices. Despite tomato being a major vegetable crop in MS, information on the N requirements for commercial production in the state is limited. Therefore, this study was conducted in an open field to determine the critical nitrogen rate for commercial tomato production under the northeast growing conditions of MS. The study evaluated six N application rates (0, 67, 101, 135, 202, and 269 kg ha-1) arranged in a randomized complete block design with four replicates per treatment. Red Duce variety of tomato was planted, and nitrogen was applied at 50% pre-plant (33-0-0) and 50% fertigation (15.5-0-0). Both potassium and phosphorus were the same for all treatments and applied at 100% pre-plant using 0-0-60 and 0-46-0 respectively. Preliminary results indicate that higher N application rates significantly increased total fruit yield, total marketable yield, fruit sizes, and total biomass. The highest total fruit yield (93.79 t ha-1), total marketable yield (71.58 t ha-1), large fruit yield (10.40 t ha-1), and total biomass (6.96 t ha-1) were observed at 269 kg N ha-1. Increasing N application rates significantly increased tissue N concentration. Therefore, the greater yield observed at higher N application rates was attributed to the consistently higher tissue N concentration from leaf samples collected at different weeks during the growing season. Based on the results obtained, the critical N application rate for open-field fresh-market tomato production in northeast MS could be up to 269 kg ha-1. However, follow-up studies are currently being conducted to validate these preliminary results.

Phosphorus (P) is a macronutrient essential for plant growth and yield; however, its availability in spodosols is often limited due to high acidity, low organic matter, and strong adsorption to soil minerals, particularly iron (Fe) and aluminum (Al) in tropic Spodosol in Northeast Florida. Efficient P management is essential for optimizing crop productivity while minimizing environmental risks. This study investigated the effects of different P fertilizer rates on Potato (Solanum tuberosum, L.) growth, yield, and nutrient dynamics at the UF/IFAS Hastings Agricultural Extension Center, Northeast Florida over two consecutive growing seasons (Spring 2022 and Sprin 2023). A randomized complete block design was employed, with five P rates of 0, 90, 135, 180, and 225 kg ha-1 of phosphorus pentoxide (P2O5) as triple superphosphate (TSP). The changes in plant growth, nutrient uptake, yield, as well as soil properties were determined to evaluate the effectiveness of P fertilization as plant growth performance and tuber yield. The results showed that P application significantly increased potato tuber yield compared to the control, with the highest yield observed at 225 kg ha-1 P2O5. Pearson correlation analysis indicated strong associations between plant growth, tuber yield, and nutrient accumulation. Principal component analysis (PCA) highlighted notable seasonal differences in tuber yield and soil characteristics. The study highlights the importance of site-specific P recommendation to synchronize nutrient availability with crop demand, particularly in nutrient-poor spodosols in Northeast Florida. These findings provide a scientific basis for establishing P fertilizer thresholds that balance crop productivity with environmental sustainability in agricultural systems.

Phosphorus is well known for being a nutrient vital for plants, influencing key stages of plant cycle. However, its efficiency can be reduced by nutrient fixation processes or leaching, with challenging strategies to enhance phosphorus availability. Hydrogel polymers have been proposed as soil amendments to improve moisture retention and nutrient uptake. This study evaluates the impact of hydrogel polymer combined with different phosphorus rates on the growth and yield of Snap Bean (Phaseolus vulgaris). The experiment consists of six phosphorus rates of 0, 100, 150, 200, 250, and 300 lbs/A P2O5, and a hydrogel rate of 30 lbs/A. Treatments were arranged in a randomized complete block design with 4 replications per treatment, and 4 rows per replication. Growth parameters such as Plant Height, Leaf chlorophyll content, weekly tissue sampling. Yield parameters such as number of pods per plant, pod weight, pod yield were also assessed. Data analysis is performed using one-way ANOVA in R Studio, with post-hoc comparisons using Tukey’s HSD test at P

Snap bean (Phaseolus vulgaris L.) is a vital crop in Florida, but it is highly vulnerable to low-oxygen (O₂) stress in soil and phosphorus (P) deficiency, particularly in regions utilizing deep well irrigation. The objective of this study was to evaluate the effects of liquid O₂ and P fertigation on plant growth, pod yield, and nutrient uptake under field conditions. A Randomized Complete Block Design (RCBD) with four replications was employed, testing two rates of liquid O₂ (0 and 45 kg ha⁻¹ as hydrogen peroxide, H₂O₂) and five levels (0, 90, 135, 180, and 225 kg ha⁻¹) of liquid P as 0-54-0 phosphoric acid (H₃PO₄). Key variables assessed included plant growth, P uptake, pod yield, and soil properties to evaluate the effectiveness of fertigation in promoting plant performance and nutrient uptake. The results indicated that both liquid O₂ and P applications enhanced plant growth and pod yield, with the highest pod yield achieved from the combination of 45 kg ha⁻¹ of liquid O₂ and 225 kg ha⁻¹ of liquid P. Pearson correlation analysis revealed strong associations between plant growth, pod yield, and nutrient uptake. Principal component analysis (PCA) confirmed the significant effects of liquid O₂ and P fertigation on growth parameters and pod yield. This study concludes that liquid O₂ fertigation alleviates soil hypoxia, improves P use efficiency, and boosts crop productivity, offering a promising and cost-effective solution for optimizing snap bean cultivation.

The pH of the root zone plays a crucial role in influencing the solubility of nutrients within a soilless substrate or hydroponic solution, affecting their uptake into plant tissue. Our objective was to re-evaluate and update the understanding of how root zone pH affects nutrient solubility in soilless substrates and hydroponic systems using chemical equilibria software, laboratory testing, and a literature review. The aim was to provide horticulture practitioners with an understanding of the trends that should be considered when managing substrates and fertilization. Calcium and magnesium have decreasing solubility with increasing pH. However, dolomitic limestone added for neutralization of acidic substrates such as bark and peat increase Ca and Mg under alkaline conditions. Because potassium salts are usually the liming sources in hydroponics, Ca and Mg levels decrease at high pH. Phosphorus availability is limited primarily because of reactions with Ca at high pH. Results demonstrated substantial differences in micronutrient solubility between sulfate-based and chelated micronutrients. In hydroponic simulations (GEOCHEM-EZ), sulfate-based micronutrients rapidly became insoluble at higher pH (>6.0), whereas chelates, particularly Fe-EDDHA (ethylenediamine-N,N-bis(2-hydroxyphenylacetic acid), maintained solubility even under alkaline conditions (up to pH 10.0). Visual MINTEQ simulations highlighted the role of DOM in stabilizing micronutrient availability in soilless substrates through the formation of metal-organic complexes, especially for metal micronutrients Fe, Cu, and Zn. Laboratory measurements were consistent with chemical equilibrium simulations, demonstrating higher water-extractable micronutrient solubility with EDTA (ethylenediaminetetraacetic acid) chelates compared with sulfate forms, particularly at elevated pH. Fe and Mn solubility sharply declined with increasing substrate pH, whereas Zn and Cu solubility peaked at intermediate pH levels (5.5 to 6.5). Boron availability decreased as substrate pH increased, whereas Mo solubility increased under alkaline conditions. A review of trends in plant tissue micronutrient concentration at different pH levels in hydroponics and soilless substrates emphasized that translating micronutrient solubility to plant availability is complex. For example, absorption of cations by roots at very low pH may be impeded in soilless substrates hydroponics by a combination of growth inhibition, nutrient disorders, and direct pH effects of H concentration. Plant uptake involves numerous biological processes, including root exudation, microbial interactions, nutrient competition, redox conditions, and plant-specific nutrient strategies. Updated pH solubility charts were developed to help visualize micronutrient solubility and plant uptake under different scenarios that have practical implications for horticulture fertilizer management.