Tomatoes are one of the most important greenhouse produced crops and the number of producers using greenhouse to grow them has risen in recent years. Sustainable development and effective resource management are becoming more and more important to the agricultural industries as well. Applying fertilizer precisely is becoming more and more important in different agricultural systems. Different physical and chemical characteristics of soilless growing substrate result in varying capacities for retaining nutrients. As a result, precise fertilizer rates are essential. This study investigated 14 fertilizer blends with varying proportions of nitrogen (0-400ppm), phosphorus (0-100ppm), and potassium (0-425). Six-cell seedling starter trays were filled with Berger BM6, and 'Big Beef' tomato seeds were planted. After four weeks, the seedlings were transplanted into five-gallon aeration fabric grow bags. Plants were hand-watered once a week with each treatment fertilizer rate to maintain a 10% leaching fraction. End measurements included the number of leaves, dry shoot weight, fresh root weight, dried root weight, and SPAD readings. The study revealed that a higher rate of nitrogen increased fresh shoot weight and lower rates of phosphorous increased number of non-harvestable fruits, increasing the need for further investigation to determine optimal fertilizer rates for various specialty crops grown in soilless greenhouse environments. Such endeavors are crucial for maximizing agricultural productivity while minimizing resource wastage and environmental impact.
Tomato (Solanum lycopersicum L.) is the number one vegetable crop in Hawaii in terms of popularity and market value. Of the total tomatoes consumed in Hawaii only 23% is produced locally. Local production has decreased substantially over the past few years due to crop losses caused primarily by the Tomato Yellow Leaf Curl Virus (TYLCV), which is vectored by whiteflies Bemisia tabaci and Bemisia argentifolii. Crop losses by TYLCV in tomato crops on Maui range between 60 to 100%. Efforts to keep plants from becoming infected, manage the rate of infection, timing, or severity of the infection are needed to protect crop health. Therefore, a new integrated pest management approach was conducted integrating the use of reflective ground cover, companion plants, insecticides, and tomato varieties resistant to TYLCV. The highest total weight (4.4 lb/pl per harvest time) was observed in the variety PS01522935 in the treatment combining reflective ground cover and companion plants and the highest marketable weight was observed in the same treatment in the varieties PS01522935 and Mesquite (3.5 lb/pl per harvest time), and the highest TYLCV infection was observed in the conventional treatment in the varieties Paisano followed by Healani, Celebrity Plus and Kewalo, and the varieties with no TYLCV infection were PS01522935, SVTD8601 and Mesquite. The use of reflective ground cover and companion plants may reduce TYLCV infections in tomato crops by reducing whitefly populations.
A growing global population and worsening global environmental change necessitate the development of improved crop varieties and cultivation techniques. In tomatoes, the world’s most popular vegetable crop, grafting has emerged as a cultivation technique for addressing these challenges through improving tomato crop vigor and stress resistance, especially to abiotic stresses that are becoming more widespread including heat, salinity, and drought stress. In order to expand the offerings of tomato rootstocks, we have conducted multiple trials to assess the beneficial impact of 10 novel tomato rootstocks on ‘Celebrity’ scion vigor and stress resistance. The rootstocks, developed by colleagues at the King Abdullah University of Science and Technology (KAUST) consist of interspecific Solanum spp. hybrids including two tetraploid hybrids. We conducted three trials to assess the impact of grafting with the novel rootstocks, including a greenhouse pot trial to quantify growth and vigor and two controlled environment trials to assess stress resistance. In each trial, ‘Celebrity ’ scions were grafted with either the novel rootstocks, ‘Maxifort’, ‘Multifort’, or left ungrafted. In the greenhouse trial, measurements of stem diameter, shoot height, shoot canopy projection area, and fresh and dry weights at harvest were used to determine overall vigor. We identified five and eight of the novel rootstock grafting combinations that outperformed the ungrafted and ‘Maxifort’-grafted plants, respectively. Additionally, measurements of SPAD and observations of foliage coloration provided initial evidence of differential nutritive requirements between the novel rootstocks. In our controlled environment trials, chlorophyll fluorescence, SPAD, and porometer data demonstrated differential susceptibility to salinity, heat, and drought stress between the rootstocks. This presentation will highlight key differences in morphological and physiological traits that assisted us in selecting a narrow set of rootstocks for a forthcoming evaluation in a passive high tunnel to demonstrate the utility of these new rootstocks.
To evaluate the efficacy of a commercial available biostimulant (a product containing friendly microorganisms like N2 fixing bacteria) on the improvement of nitrogen (N) and phosphorus (P) use efficiency in tomato, two independent field experiments were conducted in West Central Florida in the fall production season of year 2023. For both experiments, treatments included a factorial combination of two biostimulant rates (0 or 0.247 kg/ha) and four fertilizer rates (N or P2O5) (0, 67, 135, 202 or 269 kg/ha) that were arranged in a split-plot design. Biostimulant was applied as a solution drenched in soil following transplanting, and fertilizer treatments were applied as pre-plant application in soil and/or through drip injection during the season. Commercial tomato cultivar ‘HM1823’ was chosen as plant material. Analysis of variance (ANOVA) revealed that biostimulant did not have statistically significant influence on fruit marketable yield, fruit quality (Brix) and plant biomass, regardless of application rates of P2O5. By contrast, however, application of N had statistically (P
Dr. Lakesh Sharma is an assistant professor of soil fertility and sustainable agriculture at the University of Florida in Gainesville, FL. Lakesh has been farming since he was a child on his own farm. His academic school journey started in 2000. He is currently working on nutrient... Read More →
Anaerobic soil disinfestation (ASD) is a microbial-driven soil disinfestation approach for the management of soilborne pests and pathogens of horticultural crops including protected vegetable production systems increasingly affected by emerging soilborne issues. ASD is implemented by incorporating in the soil an easily labile carbon (C) source, mulching the soil with an impermeable film, and irrigating the soil to field capacity. Organic amendments used as C source also provide N and other nutrients, and research is needed to assess if and how crop fertilization should be adjusted accounting for such nutrients. A study was conducted to evaluate the effect of alternative C sources on soil nutrient availability during and post-ASD in a high tunnel tomato production system. Carbon sources tested included sugarcane molasses, wheat middlings, and soybean meal mixed with wheat middlings. Each C source was applied at the standard rate of 6 Mg/ha of total C. The same C sources were also applied at half rate (3 Mg/ha of total C) balancing the total nitrogen (N) applied to 350 kg/ha of N using composted chicken manure as a source of N. The selected C source treatments were compared with untreated soil amended only with composted chicken manure and an untreated control to estimate the amount of nutrients provided by the untreated soil or by the composted chicken manure. Post ASD, fresh-market tomato cv Red Deuce was planted and used as a test crop evaluating plant growth, nutrient uptake, and yield and quality performance in response to soil treatments. Post-ASD, soil redox potential (Eh) was monitored revealing that all C sources tested determined a significant decrease of soil Eh, suggesting a good efficacy of the ASD treatment. During and post-ASD soil pH, EC, nitrate-N and ammonium-N levels were monitored using soil-water extracts (obtained with the 1:2 v:v method). Significant variation of soil pH, EC and mineral-N content were observed during and post-ASD, which influenced tomato marketable yield. Among the treatment tested WM applied at half rate and balanced for the N which had an intermediate C:N ratio (11.65) provided the highest seasonal marketable yield (10.4 kg/plant), while the untreated control amended with chicken manure provided the lowest yield. Overall, this study suggests that C application rate and the C:N ratio of the organic amendments used to apply ASD have significant effects on the efficacy of the ASD treatment as well as on the availability of nutrients and the crop performance post-ASD.
Pepper is an important specialty crop in the Southwest U.S., cherished for its economic importance, cultural history, and high nutritional values. Despite being a leading pepper producer in the U.S., challenges such as high temperatures, erratic weather patterns, and imports from Mexico have hindered both production and profitability of growers in this region. In response, alternative systems like high tunnels have emerged as viable solutions. The mild winter climate in Southwest Texas offers an ideal setting for winter pepper cultivation in high tunnels, potentially boosting growers' profitability with off-season market opportunities. Application of biostimulants, such as seaweed extracts, holds promise in enhancing cold tolerance and transplant success within high tunnel systems. This study investigates the feasibility of winter pepper production in high tunnels established in the Wintergarden region, assessing various cultivars based on yield and quality. The high tunnel maintained a range of 8-10°C higher temperatures than the open-field on chilly days without additional heating. Seven pepper cultivars were evaluated, with and without seaweed extracts. Seaweed-treated plants exhibited an overall higher stomatal conductance and leaf transpiration rates along with reduced leaf electrolyte leakage. Rio de Oro; a Santa Fe type pepper had the highest PSII efficiency and total fruit yield. Seaweed application also increased total yield and individual fruit weight in cultivar-specific manner. The total phenolic content of fruits was increased by seaweed application at the early maturity stage whereas total flavonoid content varied by cultivar and maturity stage. Despite facing freeze challenges at the early transplant stage, this first-year experiment demonstrated promising potential for off-season pepper production in high tunnels in our region.
This study was carried out at the University of Georgia (UGA) Vidalia Research Center during the 2022/2023 winter season and is being repeated in 2023/2024. The objectives of this experiment were to identify the relationship between planting density, nitrogen fertilizer rates, and the effects on yields and bulb size distribution. The variety “Sweet Magnolia” was tested at three planting densities (116,000; 87,000; and 58,000 plants per acre) and three nitrogen rates (120, 100, and 80 lbs. per acre). Results indicated there is no interaction between planting density and nitrogen rates on onion bulb size distribution or total production. However, the effect of planting density was significant. Higher densities (116,000 plants/acre) yielded a total weight of 1788 40 lbs. bags/acre with a significant proportion of jumbo-sized bulbs 62%, while lower densities (58,000 plants/acre) resulted in larger colossal bulbs 290 40 lbs. bags/acre with a reduced total yield 1370 40 lbs. bags/acre. Nitrogen application also had a significant impact on both yield and size of the bulb. The highest nitrogen rate (120 lbs./acre) produced a higher total yield (1670 40 lbs. bag/acre), with a significant portion of jumbo at 50% and colossal bulbs at 15%. There was no significant difference between the nitrogen rates of 100 and 120 lbs./acre, but the lowest nitrogen rate (80 lbs./acre) had the worst yield with 1434 40 lbs. bags/acre resulting in a 15% decreased yield compared with the higher rate. These results suggest that optimal planting density and nitrogen application are decisive for reaching the desired bulb size distribution and maximizing yield.
The escalating impacts of climate change on agriculture necessitate the exploration of sustainable crop enhancement methods. This research integrates greenhouse screening and field application to evaluate the efficacy of biostimulants in promoting the growth of onion (Allium cepa L.) under variable environmental conditions. In the initial greenhouse experiment, seven biostimulants were tested, including three bacterial products (Continuum, Spectrum DS, and Tribus Original), two mycorrhizal products (Mighty Mycorrhizae and Myco Apply), one seaweed extract product (Seaweed), and one product containing humic acid (Huma Pro 16). These were applied to assess their impact on seedling emergence and growth in a peat-based soilless substrate. Huma Pro 16 and Spectrum DS were identified as the most effective in increasing seedling emergence, leaf area, and biomass. Based on these findings, field trials were conducted with four onion cultivars (red, sweet, white, and yellow), subjected to conditions simulating drought and normal watering (75 % and 100 % evapotranspiration) or with nitrogen levels adjusted to low and high (75 % and 100 % of optimal 168 kilograms per hectare). The field trials assessed bulb diameter, weight, and leaf metrics. Results indicated that cultivars responded differently to varying conditions, with red and white onions showing consistent growth patterns, while sweet onions displayed more variability. Yellow onions benefited from the biostimulants, exhibiting improved growth under both drought and low nitrogen conditions. This study demonstrates that the application of certain biostimulants can significantly enhance crop growth and resilience. Huma Pro 16 and Spectrum DS show promise for improving onion yield in the face of climatic challenges. Keywords: biostimulants, drought stress, nitrogen availability, onion, and sustainable agriculture.
