Effects of Irrigation Frequency and Nitrogen Fertilizer Rate on Water Stress, Nitrogen Uptake, and Plant Growth of Container-grown Rhododendron

Abstract

<jats:p>The influence of irrigation frequency (same amount of water per day given at different times) and nitrogen (N) fertilizer rate on water stress [stomatal conductance (<jats:italic>g</jats:italic><jats:sub>S</jats:sub>)], N uptake, and growth (biomass) of container-grown evergreen <jats:italic>Rhododendron</jats:italic> ‘P.J.M. Compact’ and ‘English Roseum’ and deciduous <jats:italic>Rhododendron</jats:italic> ‘Gibraltar’ was evaluated. Both N deficiency and high N rate increased water stress. Water stress was greatest in plants fertilized with the highest N rate and <jats:italic>g</jats:italic><jats:sub>S</jats:sub> of plants grown with the higher N rates changed more in response to water deficits resulting from irrigation treatments and seasonal climatic changes. Watering plants more frequently decreased water stress of plants fertilized with higher N rates and altering irrigation frequency had little impact on alleviating water stress of N-deficient plants. Increasing irrigation frequency decreased N uptake efficiency (N uptake per gram N applied), increased N use efficiency (growth per gram N uptake) and altered biomass allocation with little influence on total plant biomass. Response of biomass allocation to N rates was similar among cultivars and response of biomass allocation to irrigation frequency varied among cultivars. Altering irrigation frequency changed either the availability of N in the growing substrate or the ability of roots to absorb N. Our results indicate that transitory increases in plant water stress can alter N uptake, N use, and plant form without detectable changes in total plant biomass.</jats:p>

Cascading effects of N input on tritrophic (plant–aphid–parasitoid) interactions

“…Besides, high rates of N application may increase plant demand for water and then increase the possibility of water stress (Scagel, Bi, Fuchigami, & Regan, 2011). Many phytophagous insects, especially sap-feeders, are adversely affected by continuous water stress (reviewed in Huberty & Denno, 2004).…”

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

“…Nutrient availability declines with low soil water content, which becomes a limiting factor for nutrients to become soluble to the root surface (Marschner, 2012). Increased irrigation frequency with the same total amount of water has been used to reduce nutrient leaching and compensate for possible nutrient deficiency, and it has varying effects on plant growth and nutrient uptake (Fare et al, 1994;Scagel et al, 2011). Neilsen et al (1995) reported that higher frequency irrigation improved tree growth of 'Gala' apple (Malus domestica Borkh.)…”

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

“…Depending on the hydrophilic or hydrophobic materials that constitute the biocontainers, plants grown in biocontainers have various water-use characteristics, with some of them requiring more water or more frequent irrigation than plastic containers (Evans and Karcher, 2004;Evans et al, 2010;Koeser et al, 2013b). Water availability between irrigation events may then influence nutrient availability to the plant in the substrate (Scagel et al, 2011). The porous nature of the sidewalls of some biocontainers has resulted in greater water use, but increased evaporation was believed to help reduce substrate temperature, which is a beneficial feature at locations where summer heat stress may be a problem for plant growth or survival Wang et al, 2015).…”