Rate of nitrogen application during the growing season alters the response of container-grown rhododendron and azalea to foliar application of urea in the Autumn

et al. 2019

Plant growth, water use, photosynthetic performance, and nitrogen (N) uptake of ‘Merritt’s Supreme’ hydrangea (Hydrangea macrophylla) were investigated. Plants were fertilized with one of five N rates (0, 5, 10, 15, or 20 mm from NH4NO3), irrigated once or twice per day with the same total daily amount of water, and grown in either a paper biodegradable container or a traditional plastic container. Greater N rate generally increased plant growth index (PGI) in both plastic and biocontainers. Leaf and total plant dry weight (DW) increased with increasing N rate from 0 to 20 mm and stem and root DW were greatest when fertilized with 15 mm and 20 mm N. Plants fertilized with 20 mm N had the greatest leaf area and chlorophyll content in terms of SPAD reading. Container type had no influence on DW accumulation or leaf area. N concentrations (%) in leaves, roots, and the entire plant increased with increasing N rate. N concentrations in roots and in the entire plant were lower in biocontainers compared with plastic containers. Greater N rate generally increased daily water use (DWU), and biocontainers had greater DWU than plastic containers. The 20 mm N rate resulted in the highest net photosynthetic rate measured on 11 Sept. and 22 Sept. (65 and 76 days after treatment). Net photosynthetic rate (measured on 8 Oct.) and stomatal conductance (gS) (measured on 27 Aug., 22 Sept., and 8 Oct.) were lower in biocontainers compared with plastic containers. Two irrigations per day resulted in higher substrate moisture at 5-cm depth than one irrigation per day, and slightly increased PGI on 19 Aug. However, irrigation frequency did not affect photosynthetic rate, gS, or N uptake of hydrangea plants except in stems. Considering the increased water use of hydrangea plants when grown in the paper biocontainer and lower plant photosynthesis and N uptake, the tested paper biocontainer may not serve as a satisfactory sustainable alternative to traditional plastic containers.

Section: Discussionmentioning

confidence: 99%

Nitrogen Fertilization and Irrigation Frequency Affect Hydrangea Growth and Nutrient Uptake in Two Container Types

Li¹,

Bi²,

et al. 2019

“…Plant N status is mainly improved by application of N fertilizer. Increased N during fertilization increased plant biomass and N uptake and improved flower quality of some species, but it also increased nutrient leaching and decreased uptake efficiency (Bi and Scagel, 2008;Bi et al, 2007;Chang et al, 2012). Higher N fertilization rate promoted shoot growth of container-grown Rhododen-dron L. 'Karen' and increased nutrient leaching, whereas decreased N and P promoted root growth and improved nutrient uptake efficiency (Ristvey et al, 2007).…”

mentioning

confidence: 99%

Mineral Nutrient Uptake of Encore Azalea ‘Chiffon’ Affected by Nitrogen, Container, and Irrigation Frequency

Li¹,

Bi²,

et al. 2019

Mineral nutrient uptake of Encore® azalea ‘Chiffon’ (Rhododendron sp.) affected by nitrogen (N) rate, container type, and irrigation frequency was investigated. One-year-old azalea plants were planted in two types of 1-gallon containers: a black plastic container or a biodegradable container (also referred to as a biocontainer) made from recycled paper. Azalea plants were fertilized with 250 mL of N-free fertilizer twice weekly plus N rates of 0, 5, 10, 15, or 20 mm from ammonium nitrate (NH4NO3). All plants were irrigated daily with the same amount of water through one or two irrigations. Plants fertilized without N had the lowest concentrations of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) averaged in the entire plant, which were at deficient levels for azalea species. High N rates of 15 or 20 mm resulted in the highest plant average concentrations of P, K, Ca, and Mg. Concentrations of micronutrients including iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), and boron (B) showed varied trends affected by different treatments. With high N rates of 15 and 20 mm, paper biocontainers increased uptake of both macro- and micronutrients in terms of total nutrient content (mg or μg per plant) compared with plastic containers. One irrigation per day increased root concentrations of Cu and Zn and root contents of Fe, Zn, Cu, and B, but decreased leaf K concentration compared with two irrigations per day. The beneficial effects of high N rates and biocontainers on mineral nutrient uptake of Encore® azalea ‘Chiffon’ likely indirectly occurred through increasing plant growth.

“…Multiple blooming seasons require continuous plant growth and nutrient supply. Plant nutrient uptake is subject to a number of factors such as growth rate, climate, and cultivating conditions (Bi et al, 2007b;Gastal and Lemaire, 2002;Million et al, 2007;Scagel et al, 2007). Nutrient uptake varies among crops, between growing seasons, and between production sites (Chang et al, 2012;Pradubsuk and Davenport, 2010;Ristvey et al, 2007;Scagel et al, 2007).…”

mentioning

confidence: 99%

Seasonal Growth and Nitrogen Uptake of Encore Azalea ‘Chiffon’ Affected by Nitrogen Availability and Containers

Li¹,

Bi²,

2019

Additional index words. biocontainer, seasonal growth, Rhododendron Abstract. Plant growth and nitrogen (N) uptake of Encore Ò azalea 'Chiffon' (Rhododendron sp.) grown in a traditional plastic container or a biodegradable container made from recycled paper were investigated over the 2013 growing season. Three hundred twenty 1-year-old azalea liners, grown in two types of containers, were fertilized twice weekly with 250 mL Nfree liquid fertilizer with no N or 15 mM N from ammonium nitrate (NH 4 NO 3 ). Biweekly from 10 May to 3 Dec., five plants from each N rate and container type were selected randomly to measure plant height, widths, and leaf chlorophyll content in terms of soil-plant analysis development (SPAD) readings, and were then harvested destructively for nutrient analyses. Leaf SPAD readings and tissue N concentration were influenced mostly by N rate rather than container type, with 15 mM N producing greater values than the no-N treatment.