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This research study evaluated the suitability of controlled-release urea (CRU) as an alternate nitrogen (N) fertilizer source to conventional soluble urea (U) for tomato production under a humid, warm climate in coastal plain soils. Tomatoes are typically produced on raised plastic-mulched beds, where U is fertigated through multiple applications. On the other hand, CRU is applied once at planting, incorporated into soil before the raised beds are covered with plastic mulch. N source and management will likely impact tomato yield, N use efficiency (NUE), and apparent recovery of N fertilizer (APR). A 2-year field study was conducted on fall and spring tomato crops in north Florida to determine the crop N requirement and NUE in tomatoes (var. HM 1823) grown in sandy soils under a plastic-mulched bed system. In addition to a no N fertilizer treatment, three urea N sources [one soluble source and two polymer-coated CRU sources with different N release durations of 60 (CRU-60) and 75 (CRU-75) days] were applied at three N rates (140, 168, and 224 kg⋅ha−1). Across all N sources and N rates, fall yields were at least 20% higher than spring seasons. At the 140 kg⋅ha−1 N rate, APR and NUE were improved, especially when U was applied in fall tomato, whereas preplant CRUs improved N efficiency in spring tomato. Based on the lower APR values found in spring production seasons (0% to 16%) when compared with fall (57.1% to 72.6%), it can be concluded that residual soil N was an important source for tomatoes. In addition, the mean whole-plant N accumulation of tomato was 102.5 kg⋅ha−1, further indicating that reducing the N rate closer to crop N demand would greatly improve conventional vegetable production systems on sandy soils in north Florida. In conclusion, polymer-coated CRU and fertigation U applications were able to supply the N requirement of spring and fall tomato at a 38% reduction of the recommended N rate for tomato in Florida (224 kg⋅ha−1). Preliminary results show that adoption of CRU fertilizers can be considered a low-risk alternative N source for tomato production and the ease of applying CRU once during the bed preparation period for tomato may be an additional incentive.

Open Access

Reusing irrigation water has technical, environmental, and financial benefits. However, risks are also associated with the accumulation of agrochemicals, in addition to ions, plant and food safety pathogens, and biofilm organisms. In this project, we measured the concentration of paclobutrazol (a persistent and widely used plant growth regulator) in recirculated water in greenhouses producing ornamental plants in containers. Solutions were collected from catchment tanks at nine commercial greenhouses across seven states in the United States in Spring and Fall 2014. Paclobutrazol was detected in all samples, with differences observed by season, greenhouse operation, paclobutrazol application method, and irrigation method. Across operations, the residual concentration of paclobutrazol was higher in spring for most greenhouses (ranging from 0 to 1100 µg·L−1) compared with the fall (ranging from 0 to 8 µg·L−1). The spray-drench application method resulted in the highest residual concentrations (up to 35 µg·L−1), followed by substrate drench (up to 26 µg·L−1) and foliage spray (concentrations under 3 µg·L−1). Residual concentrations were higher with overhead irrigation (up to 35 µg·L−1) compared with subirrigation systems (up to 15 µg·L−1). Our results indicate that paclobutrazol is likely to be a growth retardant risk in greenhouse operations recirculating water. A clear understanding of the risks associated with recirculated water intends to support the development and implementation of risk management strategies to ensure and promote safe use of recirculated water in greenhouses. Overall, the most effective preventative strategy is to ensure the use of the minimum amount of the a.i. necessary per unit of space and time.

Open Access

Plants native to the United States, defined as those being present before European settlement, have aesthetic and environmental benefits. In 2018, only 10% of plant sales were native plants, a plant category that tends to be underrepresented in many residential and commercial landscapes. Although earlier research indicated that consumers find native plants less aesthetically appealing relative to introduced species, more recent research reported a growing demand for native plants. Thus, a better understanding of consumer perceptions would facilitate their marketing. We used an online survey of 1824 participants representing five geographic regions (West, Southwest, Midwest, Southeast, and Northwest) to classify adopters based on their purchase of native plants. A double-hurdle model was used to estimate factors influencing purchasing native plants among US homeowners, and the factors influencing the amount spent on native plants in 2021. Demographically, metropolitan, college-educated, and younger participants were more likely to be native plant adopters; they also spent 80% more on plants compared with nonnative plant adopters. More native plant adopters agreed that native plants were better for the environment than exotic plants (68%), are readily available in their area (67%), and are better adapted to difficult sites (75%). Marketing efforts should capitalize on the environmental benefits to stimulate purchases.

Open Access

Young almond (Prunus amygdalus) orchards replanted where old orchards of stone fruits (Prunus sp.) have been removed are subject to physical, chemical, and biotic stressors. Among biotic challenges, for example, is almond/stone fruit replant disease (ARD; formally known as Prunus replant disease), which specifically suppresses the growth and yields of successive almond and other stone fruit plantings and is caused, in part, by a soil microbial complex. During four orchard trials representing different almond replant practices and scenarios in the San Joaquin Valley in California, we examined the impacts of phosphorus (P) fertilization on the growth of replanted almond. During all trials, P was applied to tree root zones just after replanting, and the impact was assessed according to trunk cross-sectional area (TCSA) growth for 2 years. Expt. 1 was performed where a previous almond orchard was cleared using whole orchard recycling (i.e., the old orchard was “chipped” and then turned into the soil). The land was replanted without preplant soil fumigation. We tested separate fertilizer treatments based on various P, nitrogen, micronutrient, and “complete” formulations. Expt. 2 was also performed where an old almond orchard was recycled, but the soil was preplant-fumigated before replanting. Here, we tested only P fertilization. Expts. 3 and 4 were conducted where an old peach (Prunus persica) orchard was removed. Here, P and nitrogen fertilizer treatments were tested among additional factors, including preplant soil fumigation (Expts. 3, 4) and whole orchard recycling chips (Expt. 4). During all four trials, P fertilization (P at 2.2 to 2.6 oz/tree within a few weeks after planting) significantly increased TCSA growth. The growth benefit was nuanced, however, by almond cultivar, date of replanting, rootstock, and other site-specific factors. Although P fertilization did not match the benefit of preplant soil fumigation for the management of ARD, our data indicated that P fertilization can improve the growth of young almond orchards in diverse replant settings with or without preplant soil fumigation and should be considered by California almond producers as a general best management practice.

Open Access

This study shows that plasma-fixed nitrogen applied as an inorganic biostimulant can improve marketable lettuce (Lactuca sativa var. longifolia) yield following delayed harvest. Using just one-tenth of the conventional nitrogen, plasma-fixed nitrogen—which is generated by a dielectric barrier discharge over water—was field-tested against traditional fertilization methods. Although no statistically significant differences were observed in total weight of heads among treatments, plasma-fixed nitrogen–treated plants had significantly increased marketable yields of 250% compared to those grown conventionally, despite reducing applied nitrogen fertilizer.

Open Access

Near infrared (NIR) spectroscopy can be applied to nondestructively assess soluble solids concentration (SSC) of ripening, physiologically mature ‘Geneva 3’ kiwiberries (Actinidia arguta). Spectrographic signatures were captured using a handheld NIR produce quality meter to build predictive models of internal fruit quality for ‘Geneva 3’ kiwiberries that had been held under cold storage (CS) conditions (0 to 1 °C, >90% relative humidity) as well as those not subjected to CS. The CS model, constructed using scans of 133 berries following 4 to 6 weeks in CS, predicts SSC using NIR wavelengths in the range of 729 to 975 nm. A total of 507 berries fresh from the vine were used to construct a predictive model for SSC of non-CS fruit using the same wavelength range. In each case, model predictive performance was investigated using split-half cross-validation, resulting in mean absolute error (MAE) values of 1.2% and 0.8% SSC for the CS and non-CS model, respectively. Each full model was then used to predict SSC of kiwiberries subjected to the alternative CS condition. The non-CS model maintained a low MAE (1.6% SSC) when applied to CS fruit, but the MAE of the CS model applied to non-CS fruit rose considerably (4.5% SSC). The performance of a combined model was tested against both CS and non-CS models, and a benefit to using tailored, CS-specific models was found, particularly in light of cross-seasonal results. As it has proven in many crops, NIR spectroscopy appears to be a promising tool for nondestructively assessing SSC in ‘Geneva 3’ kiwiberry fruit, with accuracy being enhanced by training models specific to postharvest regimes and/or defined ranges of SSC.

Open Access

Mutants are useful for determining the genes that underlie a given trait. This information is highly useful for developing molecular markers for breeding and is the foundational knowledge required for future genomic crop improvements. The dessert strawberry, Fragaria ×ananassa, is a valuable crop with high potential for increased use in controlled environment agriculture. The genome of the woodland strawberry Fragaria vesca is the dominant genome of the four diploid strawberry subgenomes that contribute to the octoploid F. ×ananassa genome. F. vesca is therefore a useful reference system for determining gene function and should be a useful source of gene diversity for breeding of F. ×ananassa. Chemical mutagenesis of the inbred F. vesca line H4 F7-3 resulted in one M2 line with a smaller stature overall and which produces flowers on very short peduncles close to the crown. This line was named short inflorescence (sin). The sin phenotype results from a single gene recessive mutation that is pleiotropic in that the mutation also affects internode lengths of runners as well as petiole elongation of sin plants. Microscopic characterization revealed that sin peduncles are most likely short because of a failure of cells to elongate. Inflorescences, runners, and petioles of sin plants were found to elongate in response to exogenous gibberellin, indicating that sin could be a gibberellin biosynthesis or transport mutant. A brief characterization of sin plants is presented to facilitate collaborative studies of the line.

Open Access

Northern bayberry [Morella (formerly Myrica) pensylvanica] is an attractive, adaptable, semievergreen, northeastern North American native shrub that is sought for landscaping but difficult to propagate clonally. The impact of timing (June, July, or August) and concentration of indole-3-butyric acid [IBA (0, 2000, 4000 or 8000 ppm)] on propagation by stem cuttings was evaluated for genotypes of northern bayberry including the female cultivars Bobzam (Bobbee™) and UConn Compact and an unnamed male. Medium formulation and cytokinin type were evaluated for micropropagation of ‘Bobzam’ and ‘UConn Compact’. Stem cuttings of ‘Bobzam’ and ‘UConn Compact’ rooted poorly (at ≤55% and ≤20%, respectively) at all timings and concentrations of IBA; however, rooting success of ≥85% was achieved for the unnamed male genotype when cuttings were taken in June. Micropropagation of ‘Bobzam’ was successful using Woody Plant medium with 4 mg·L−1 zeatin and explants taken from shoots that had expanded 12 to 18 cm on containerized stock plants. Initiated explants of ‘Bobzam’ required eight subcultures before they began to produce shoots consistently at a 2× multiplication rate and eventually reached a 3× multiplication rate. Micropropagation attempts using Murashige and Skoog medium, the cytokinins 6-benzylaminopurine, meta-topolin, and thidiazuron, or the cultivar ‘UConn Compact’ were unsuccessful. Microshoots of ‘Bobzam’ rooted at ≥80% either by in vitro prerooting or ex vitro rooting directly in trays. Rooted microcuttings easily acclimated to greenhouse conditions and grew rapidly when potted to 1.04-L containers and then into 5.68-L containers. The micropropagation protocol developed for ‘Bobzam’ can be used by propagators to expand production of this popular female cultivar.

Open Access

Overwinter mustard cover crops incorporated into soil may suppress early-season weeds in chile pepper (Capsicum annuum). However, the potential for mustard cover crops to harbor beet leafhoppers (Circulifer tenellus) is a concern because beet leafhoppers transmit beet curly top virus to chile pepper. The objectives of this study were to determine the amounts of a biopesticidal compound (sinigrin) added to soil from ‘Caliente Rojo’ brown mustard (Brassica juncea) cover crops ended on three different days before beet leafhopper flights during spring and to determine the effects of the cover crop termination date on weed densities and hand-hoeing times for chile pepper. To address these objectives, a field study was conducted in southern New Mexico. In 2019–20, the cover crop was ended and incorporated into soil 45, 31, and 17 days before beet leafhopper flights. In 2020–21, cover crop termination occurred 36, 22, and 8 days before beet leafhopper flights. Treatments also included a no cover crop control. Cover crop biomass and sinigrin concentrations were determined at each termination. Chile pepper was seeded 28 days after the third termination date. Weed densities and hand-hoeing times were determined 28 and 56 days after chile pepper seeding. In 2019–20, the third termination (17 days before beet leafhopper flights) yielded the maximum cover crop biomass (820 g⋅m−2) and greatest sinigrin addition to soil (274 mmol⋅m−2). However, only the second termination (31 days before beet leafhopper flights) suppressed weeds in chile pepper. In 2020–21, the third termination (8 days before beet leafhopper flights) yielded the maximum cover crop biomass (591 g⋅m−2) and greatest sinigrin addition to soil (213 mmol⋅m−2), and it was the only treatment that suppressed weeds. No cover crop treatment reduced hand-hoeing times. These results indicate that overwinter mustard cover crops can be ended to evade beet leafhopper flights and suppress weeds in chile pepper.

Open Access