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

Abstract

<jats:p>Plant growth, water use, photosynthetic performance, and nitrogen (N) uptake of ‘Merritt’s Supreme’ hydrangea (<jats:italic>Hydrangea macrophylla</jats:italic>) were investigated. Plants were fertilized with one of five N rates (0, 5, 10, 15, or 20 m<jats:sc>m</jats:sc> from NH<jats:sub>4</jats:sub>NO<jats:sub>3</jats:sub>), 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 m<jats:sc>m</jats:sc> and stem and root DW were greatest when fertilized with 15 m<jats:sc>m</jats:sc> and 20 m<jats:sc>m</jats:sc> N. Plants fertilized with 20 m<jats:sc>m</jats:sc> 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 m<jats:sc>m</jats:sc> 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 (<jats:italic>g</jats:italic><jats:sub>S</jats:sub>) (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, <jats:italic>g</jats:italic><jats:sub>S</jats:sub>, 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.</jats:p>

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

“…Greater dry root weight of cyclamen (Cyclamen persicum) was found using paper and wood fiber containers compared with plastic containers (Beeks and Evans, 2013). The porous sidewall of the paper biocontainer used in the current study was found to increase water use as a result of water loss through the container sidewall Wang et al, 2015), which reduced stomatal conductance and increased water stress of Hydrangea macrophylla in our previous study (Li et al, 2019). However, the evaporative cooling effect as a result of sidewall water loss may be beneficial for plant root growth and survival at locations with hot summer conditions .…”

“…Such a significant difference occurred in September on 13 Sept. or 26 Sept., and this trend remained to the end of the growing season on 3 Dec. Sustainable alternative containers of various types have been reported to produce plants of similar quality compared with conventional plastic containers (Beeks and Evans, 2013;Koeser et al, 2013b;Kuehny et al, 2011;Li et al, 2015Li et al, , 2019. Paper (also referred to as wood pulp) biocontainers pro-duced river birch (Betula nigra) plants of comparable PGI and plant biomass to plastic containers in a pot-in-pot production system (Li et al, 2015).…”

“…Each azalea plant was fertilized twice weekly with 250 mL N-free fertilizer, 0N-2. GreenCare Fertilizers, Kankakee, IL) (Li et al, 2019), with either no N or 15 mM (210 mg · L -1 ) N from NH 4 NO 3 from 23 Apr. (14 d after transplanting) to 15 Sept. 2013 (159 d after transplanting), totaling 42 fertilization events with 52.5 mg N delivered at each time.…”

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

“…Scagel et al (2012) reported that net uptake of P, B, and Mn decreased in response to more frequent irrigation in container-grown Rhododendron 'P.J.M Compact', 'English Roseum', and 'Gibraltar', but increased Ca uptake of 'P.J.M Compact' and 'English Roseum'. Plant species vary in their growth and nutrient uptake responses to irrigation frequency (Li et al, 2018(Li et al, , 2019.…”

“…Biocontainers made from various biodegradable materials have been investigated as sustainable alternatives to conventional plastic containers for various crops and production systems Evans, 2013a, 2013b;Evans and Hensley, 2004;Evans and Karcher, 2004;Kuehny et al, 2011;Li et al, 2015Li et al, , 2018Li et al, , 2019White, 2009). They were reported to have varying physical properties, water consumption characteristics, and influences on plant growth.…”