Growth and quality response of four container-grown nursery crop species to low-phosphorus controlled-release fertilizer

Authors: Shreckhise, Jacob - Jake; Owen Jr, James - Jim; NIEMIERA, ALEXANDER - Virginia Tech; Altland, James

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2022
Publication Date: 9/20/2022
Citation: Shreckhise, J.H., Owen Jr, J.S., Niemiera, A.X., Altland, J.E. 2022. Growth and quality response of four container-grown nursery crop species to low-phosphorus controlled-release fertilizer. HortTechnology. 32(5):447-458. https://doi.org/10.21273/HORTTECH05058-22.
DOI: https://doi.org/10.21273/HORTTECH05058-22

Interpretive Summary: The amount of phosphorus conventionally recommended and applied to container nursery crops commonly exceeds plant requirements, resulting in unused phosphorus leaching from containers and potentially impacting the surrounding ecosystem. To determine how the phosphorus levels in fertilizer affects plant growth and nursery plant quality, a team of ARS scientists compared the effects of a low-phosphorus controlled-release fertilizer versus a conventional formulation on plant shoot growth, crop quality, and substrate nutrient concentrations. In trials with crapemyrtle, rose, azalea, and arborvitae, they found that plants that received the low-phosphorus fertilizer had less shoot growth compared to those fertilized with the conventional fertilizer; however, plant quality of rose and arborvitae was similar between both treatments. This research suggests that reducing phosphorus fertilization, even to the point of growth limitation, may not affect salability of some nursery crops. Further research is needed to define which traits are associated with perceived quality of woody ornamentals fertilized with low-phosphorus controlled-release-fertilizer.

Technical Abstract: The amount of phosphorus (P) conventionally recommended and applied to container nursery crops commonly exceed plant requirements, resulting in unused P leaching from containers and potentially contributing to surface water impairment. An experiment was replicated in the Middle Atlantic Coastal Plain (MACP) and Ridge and Valley (RV) ecoregions of Virginia to compare the effect of low-P controlled-release fertilizer (CRF) versus a conventional CRF formulation on plant shoot growth, crop quality, and substrate nutrient concentrations of four taxa: Lagerstroemia L. ‘Natchez’ (crape myrtle), Rhododendron L. ‘Roblec’ (azalea), Rosa L. ‘Radrazz’ (Knock Out rose), and Thuja L. ‘Green Giant’ (arborvitae). In both ecoregions, the low-P CRF resulted in 9% to 26% lower shoot dry weight (SDW) in all four taxa, but quality ratings for two economically important taxa, Knock Out rose and arborvitae, were similar between treatments. When fertilized with the low-P CRF, azalea and crape myrtle at both ecoregions and arborvitae at the MACP ecoregion had ˜ 56% to 75% lower substrate pore-water P concentrations than those that received the control CRF. Nitrate-nitrogen concentrations in substrate pore-water at week 5 were over six times higher in control-fertilized plants than in those that received a low-P CRF. Lower water-extractable pore-water P and N indicate less environmental risk and potentially increased crop efficiency. Our results suggest low-P CRFs can be used to successfully produce economically important ornamental nursery crops without sacrificing quality; however, early adopters will need evaluate the effect of low-P CRFs on crop quality of specific species before implementing on a large scale.