Search Results

You are looking at 21 - 30 of 42 items for

  • Author or Editor: Guihong Bi x
  • Refine by Access: All x
Clear All Modify Search
Full access

Carolyn F. Scagel, Richard P. Regan, and Guihong Bi

A study was conducted to determine whether the nitrogen (N) status of nursery-grown green ash (Fraxinus pennsylvanica ‘Summit’) trees in the autumn is related to bud necrosis during the following spring. In 2005, different rates of N from urea formaldehyde (UF) or a controlled-release fertilizer (CRF) containing ammonium nitrate were applied during the growing season to green ash trees and leaves were sprayed or not with urea in the autumn. Biomass and N content was determined in Autumn 2005 and Spring 2006, and stem biomass and bud necrosis were evaluated for necrosis in Spring 2006. Trees with low N content in Autumn 2005 grew less in Spring 2006 but bud necrosis was more prevalent on trees grown at the highest N rate. Compared with trees grown with a similar amount of N from UF, growing trees with CRF altered N allocation in 2005 and the relationship between carbon (C) and N dynamics (import, export, and metabolism) in stems in 2006. Additionally, trees grown with CRF had less total shoot biomass in Spring 2006 and more bud failure than trees grown with a similar N rate from UF. Significant relationships between bud failure and N status and C/N ratios in different tissues suggest that a combination of tree N status and the balance between N and C in certain tissues plays a role in the occurrence of bud failure of green ash trees in the spring.

Free access

Carolyn F. Scagel, Guihong Bi, Leslie H. Fuchigami, and Richard P. Regan

The influence of fall sprays with urea on the uptake of nutrients other than nitrogen (N) was assessed using 1-year-old container-grown Rhododendron L. (Rhododendron ‘H-1 P.J.M’) and azalea (Rhododendron ‘Cannon's Double’) grown with different rates of N. Plants were grown with a complete fertilizer containing different N rates from May to Sept. 2004 sprayed or not with urea in the fall of 2004 and grown with a complete fertilizer containing different N rates in the spring of 2005. Urea sprays altered uptake of nutrients other than just N although fertilizer application with other nutrients ceased before plants were sprayed with urea. Across a wide range of plant sizes and N status, urea sprays increased net phosphorus (P), copper (Cu), and manganese (Mn) uptake and decreased net potassium (K) and magnesium (Mg) uptake during the year of urea application. Spraying plants with urea altered nutrient demand and storage in different plant structures during the winter. For azalea, urea sprays increased P demand by roots, Mn demand by 2004 stems, and Cu demand by stems. Urea also decreased storage of K in roots and 2004 stems of azalea and Mg in roots. For rhododendron, urea sprays increased P demand by 2003 stems and 2004 leaves and Mn demand by 2004 leaves. Urea sprays also decreased storage of K and Mg in 2004 leaves of rhododendron. For both cultivars, urea sprays increased mobilization of iron (Fe) from storage and demand for Fe in stems. Spraying Rhododendron with urea in the fall altered uptake and demand for certain nutrients during the following spring. Urea sprays in the fall of 2004 increased uptake and possibly demand for P, K, and sulfur during the spring of 2005 for both cultivars, the uptake of calcium by rhododendron, and the uptake of Mg and Mn by azalea. Our results indicate that when growers spray plants with urea in the fall, spring fertilizer practices may need to be modified to account for increased uptake or demand of certain nutrients.

Free access

Xiaojie Zhao, Guihong Bi, Richard L. Harkess, Jac J. Varco, Tongyin Li, and Eugene K. Blythe

Tall bearded (TB) iris (Iris germanica L.) has great potential as a specialty cut flower due to its fragrance and showy, multicolor display; however, limited research has been reported on optimal nitrogen (N) nutrient management for TB iris. The objectives of this study were to investigate the effects of N fertilizer rate on plant growth and flowering of ‘Immortality’ iris and determine the influence of both stored N and spring-applied N fertilizer on spring growth and flowering. On 14 Mar. 2012, rhizomes of ‘Immortality’ iris were potted in a commercial substrate with no starter fertilizer. Plants were fertigated with 0, 5, 10, 15, or 20 mm N from NH4NO3 twice per week from 28 Mar. to 28 Sept. 2012. In 2013, half of the plants from each of the 2012 N rate were supplied with either 0 or 10 mm N from 15NH4 15NO3 twice per week from 25 Mar. to 7 May 2013. Growth and flowering data including plant height, leaf SPAD, number of fans and inflorescence stems, and length of inflorescence stem were collected during the growing season. Plants were harvested in Dec. 2012 and May 2013 to measure dry weight and N concentration in leaves, roots, and rhizomes. Results showed higher 2012 N rates increased plant height, leaf SPAD reading, and number of inflorescence stems at first and second blooming in 2012. Greater 2012 N rates also increased plant dry weight and N content in all structures, and N concentration in roots and rhizomes. Rhizomes (58.8% to 66.3% of total N) were the dominant sink for N in Dec. 2012. Higher 2012 N rates increased plant height, number of fans, and the number of inflorescence stems at spring bloom in 2013. In May 2013, N in leaf tissue constituted the majority (51% to 64.3%) of the total plant N. Higher 2012 N rates increased total dry weight, N concentration, and N content in all 2013 15N rates; however, leaf dry weight in all plants was improved by 2013 15N rate. Percentage of tissue N derived from 2013 15N (NDFF) decreased with increasing 2012 N rate. New spring leaves were the dominant sink (56.8% to 72.2%) for 2013 applied 15N. In summary, ‘Immortality’ iris is capable of a second blooming in a growing season, this second blooming dependent on N fertilization rate in current year. A relatively high N rate is recommended to produce a second bloom.

Free access

Pinghai Ding, Shufu Dong, Lailiang Cheng, Guihong Bi, and Leslie H. Fuchigami

Near-infrared (NIR) reflectance spectroscopy was used to determine the chemical composition of fruit and nut trees. Potted almond and bench-grafted Fuji/M26 trees were fertigated during the growing season with different N levels by modifying the Hoagland to create different levels of nitrogen and carbohydrates in plant tissues during dormancy. Dried, ground, and sieved shoot, shank, and root samples were uniformly packed into NIR cells and scanned with a Foss NIRSystem 6500 monochromator from 400 to 2500 nm. Statistical and multiple linear regression methods were used to derive a standard error of performance and the correlation between NIR reading and standard chemical composition analysis (anthrone, Kjedahl and Ninhydrin methods for carbohydrate, total N, and amino acid analysis, respectively) were determined. The multiple determination coefficients (R 2) of apple and almond tissues were 0.9949 and 0.9842 for total nitrogen, 0.9971 and 0.9802 for amino acid, and 0.8889 and 0.8687 for nonstructural carbohydrate, respectively.

Free access

Carolyn F. Scagel, Guihong Bi, Leslie H. Fuchigami, and Richard P. Regan

The influence of nitrogen (N) fertilizer application on plant allocation, uptake, and demand for other essential nutrients was evaluated from May 2005 to Feb. 2006 in evergreen Rhododendron ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER) and deciduous Rhododendron ‘Gibraltar’ (AZ) grown in containers filled with soilless substrate. Net nutrient uptake and losses were calculated using piecewise regression and uptake efficiency, root absorption capacity, aboveground demand, nutrient use efficiency, and uptake ratios between N and other nutrients (N ratios) were calculated using net uptake between harvest dates. Nitrogen application increased uptake rate of all nutrients, enhanced late-season uptake of many nutrients, and increased the rate of nutrient loss during the winter. Nutrient uptake often occurred as late as November in plants grown with N but was usually undetectable after September in plants grown without additional N fertilizer. Nutrient losses during the winter were not always associated with biomass loss and were related to differences in preferential nutrient allocation to different structures and the plant's ability to export nutrients before biomass loss. Plants with a greater potential for rapid growth were more capable of later-season nutrient uptake than plants with slower growth rates. Nitrogen availability altered N ratios indicating that when adding N to container-grown Rhododendron, fertilizers with higher ratios of N/phosphorus (PJM, AZ), N/calcium (PJM, ER), N/boron (PJM AZ), N/copper (PJM, ER), and N/iron (PJM, ER) and lower ratios of N/potassium (PJM, ER, AZ), N/sodium (PJM, ER, AZ), N/calcium (AZ), N/boron (ER), N/manganese (AZ), and N/zinc (ER) may be needed to optimize growth and minimize nutrient inputs. Increasing N availability altered uptake efficiency, root absorption capacity, aboveground demand, and nutrient use efficiency for several nutrients, indicating that changes in N management practices need to consider how altering N application rates may influence the plant's ability to take up and use other nutrients. This information can be used to develop fertilizer formulations to minimize excess application of nutrients and to evaluate the potential effects of altering N management practices on use of production resources. Our results indicate that nutrient management strategies for perennial crops such as Rhododendron need to take into consideration not only the nutrient demand for current growth, but also how to optimize nutrient availability for uptake that contributes to future growth potential and end-product quality.

Free access

Shufu Dong, Lailiang Cheng, Pinghai Ding, Guihong Bi, and Leslie H. Fuchigami

One-year-old (Old Home) OH87 and OH97 pear rootstocks were grown in 2-gallon containers under natural conditions at Corvallis, Ore., in in 1999. Uniform plants were harvested during August and September, and total leaf area, new shoot number and length, and root growth were measured. The kinetics of NH4 + and NO3 - uptake by new roots of both rootstocks were determined with the ion-depletion technique. OH87 had larger total leaf area, and more and longer shoots than OH97. Total root biomass was similiar between the two rootstocks, but OH87 had a larger proportion of new roots and more extension roots than OH97. Both rootstocks had lower Km values for NH4 + absorption than for NO3 - and therefore both had greater absorptive power for NH4 + than for NO3 - at the low nutrient concentrations. The maximum uptake rates (Vmax) of OH97 were similiar for both NH4 + and NO3 - absorption, but OH87 had a much higher maximum uptake rate for NO3 - than for NH4 +.

Free access

Tongyin Li, Guihong Bi, Richard L. Harkess, Geoffrey C. Denny, Eugene K. Blythe, and Xiaojie Zhao

One-year-old liners of Encore® azalea ‘Chiffon’ (Rhododendron sp.) were transplanted in Apr. 2013 into two types of one-gallon containers: black plastic container and paper biodegradable container. Azalea plants were fertilized with 250 mL of nitrogen (N) free fertilizer solution twice weekly plus N rate of 0, 5, 10, 15, or 20 mm from ammonium nitrate (NH4NO3). All plants were irrigated with the same total volume of water through one or two irrigations daily. Plant growth and N uptake in response to N fertilization, irrigation frequency, and container type were investigated. The feasibility of biodegradable paper containers was evaluated in 1-year production of Encore® azalea ‘Chiffon’. Paper biocontainers resulted in increased plant growth index (PGI), dry weights (leaf, stem, root, and total plant dry weight), leaf area, and root growth (root length and surface area) compared with plastic containers using N rates from 10 to 20 mm. Biocontainer-grown plant had more than twice of root length and surface area as plastic container–grown plant. Leaf SPAD reading increased with increasing N rate from 0 to 20 mm. One irrigation per day resulted in greater PGI, root dry weight, root length, root surface area, and root N content than two irrigations per day. Higher tissue N concentration was found in plants grown in plastic containers compared with those grown in biocontainers when fertilized with 15 or 20 mm N. However, N content was greater for plants grown in biocontainers, resulting from greater plant dry weight. The combinations of plastic container and one irrigation per day and that of 20 mm N and one irrigation per day resulted in best flower production, 21.9 and 32.2 flowers per plant, respectively. Biocontainers resulted in superior vegetative growth of azalea plant compared with plastic containers with sufficient N supply of 10, 15, and 20 mm.

Free access

Xiaojie Zhao, Guihong Bi, Richard L. Harkess, Jac J. Varco, and Eugene K. Blythe

This study investigated how spring nitrogen (N) application affects N uptake and growth performance in tall bearded (TB) iris ‘Immortality’ (Iris germanica L.). Container-grown iris plants were treated with 0, 5, 10, 15, or 20 mm N from 15NH4 15NO3 through fertigation using a modified Hoagland’s solution twice a week for 6 weeks in Spring 2013. Increasing N rate increased plant height, total plant dry weight (DW), and N content. Total N content was closely related to total plant DW. The allocation of N to different tissues followed a similar trend as the allocation of DW. In leaves, roots, and rhizomes, increasing N rate increased N uptake and decreased carbon (C) to N ratio (C/N ratio). Leaves were the major sink for N derived from fertilizer (NDFF). As N supply increased, DW accumulation in leaves increased, whereas DW accumulation in roots and rhizomes was unchanged. This indicates increasing N rate contributed more to leaf growth in spring. Nitrogen uptake efficiency (NupE) had a quadratic relationship with increasing N rate and was highest in the 10 mm N treatment, which indicates 10 mm was the optimal N rate for improving NupE in this study.

Free access

Carolyn F. Scagel, Guihong Bi, Leslie H. Fuchigami, and Richard P. Regan

The influence of irrigation frequency (same amount of water per day given at different times) on nutrient uptake of container-grown evergreen Rhododendron ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER) and deciduous Rhododendron ‘Gibraltar’ (AZ) grown with different rates of nitrogen (N) fertilizer was evaluated. Increased N application rate increased nutrient uptake and plant dry biomass. Irrigation frequency did not significantly influence total plant dry biomass; however, more frequent irrigation decreased net uptake of several nutrients including phosphorus (P), boron (B), and manganese (Mn) uptake in all cultivars; potassium (K), copper (Cu), and zinc (Zn) uptake in AZ and ER; sulfur (S) uptake in ER and PJM; and iron (Fe) uptake in AZ. Additionally, more frequent irrigation of evergreen cultivars increased calcium (Ca) uptake. Covariate analyses were used to compare nutrient uptake among cultivars and irrigation treatments after accounting for the variability in nutrient uptake attributable to differences in biomass and N uptake. For most nutrients, the influence of irrigation frequency on uptake was partially attributable to differences in biomass and N uptake. After accounting for the variability in nutrient uptake associated with biomass or N uptake, increased irrigation frequency decreased P, S, B, Cu, and Mn uptake only in ER and increased Ca uptake in the two evergreen cultivars. Differences in nutrient uptake among cultivars in response to irrigation treatments were related to water and N availability during production and their combined influence on water stress, nutrient uptake, and biomass partitioning. Estimates of nutrient demand and uptake efficiency using nutrient concentrations and ratios are discussed in relation to nutrient management differences for different cultivars and irrigation treatments.

Free access

Carolyn F. Scagel, Guihong Bi, David R. Bryla, Leslie H. Fuchigami, and Richard P. Regan

One deciduous cultivar of Rhododendron L., Gibraltar (AZ), and two evergreen cultivars, P.J.M. Compact (PJM) and English Roseum (ER), were grown in containers for 1 year to determine the effects of irrigation frequency during container production on plant performance the next spring when the plants were transplanted into the landscape. While in the containers, each cultivar was irrigated once or twice daily, using the same amount of water per day, and fertilized with complete nutrient solutions containing 0, 35, 70, or 140 mg·L−1 nitrogen (N). Three months after transplanting into the landscape, nutrient uptake, growth, and flowering were evaluated. In general, the effects of irrigation frequency in containers on performance in the landscape differed between the deciduous cultivar and the evergreen cultivars. In AZ, less frequent irrigation in containers had a pre-conditioning effect that resulted in greater vegetative growth in the landscape but less reproductive growth. In contrast, less frequent irrigation reduced vegetative growth of evergreen cultivars in the landscape and improved flowering. Different growth responses to irrigation frequency between deciduous and evergreen cultivars appeared to be related to differences in timing of nutrient uptake and mobilization. In the deciduous cultivar, less frequent irrigation increased nutrient reserves and improved the ability of the plants to absorb and use nutrients after transplanting, but in the evergreen cultivars, it generally decreased nutrient uptake after transplanting. Less frequent irrigation also altered plant attributes that are important to consumers, including developing a sparser canopy in ER and a fuller canopy in PJM, and producing more but smaller inflorescences in both cultivars. Landscape performance was related to plant nutrition in containers; however, irrigation frequency in containers disrupted relationships between nutrition and performance in all three cultivars. Our results indicate that irrigation frequency during container production of Rhododendron results in a tradeoff between vegetative and reproductive growth the next spring when the plants are in the landscape.