Effect of irrigation, fertilizer rate and placement, and two substrates on growth of rose and hydrangea

Authors: AMMONS, ANELLE - North Carolina State University; LEBUDE, ANTHONY - North Carolina State University; Owen Jr, James - Jim; MCGINNIS, MICHELLE - North Carolina Department Of Agriculture

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2022
Publication Date: 10/4/2022
Citation: Ammons, A., LeBude, A.V., Owen Jr, J.S., McGinnis, M. 2022. Effect of irrigation, fertilizer rate and placement, and two substrates on growth of rose and hydrangea. Journal of Environmental Horticulture. 40(3):123-128. https://doi.org/10.24266/2573-5586-40.3.123.
DOI: https://doi.org/10.24266/2573-5586-40.3.123

Interpretive Summary: There is an ever-increasing need to more effectively use water and mineral nutrient resources to maximize profitability, minimize environmental impact, and ensure climate resiliency. Screaming Neon Red™ rose and Endless Summer® Bloomstruck® hydrangea were produced in ~2 gal of substrate with differing water to air ratio, controlled release fertilizer (CRF) application method, CRF rate, and received two differing irrigation volumes via daily cyclic irrigation over an 18-week period. A reduction in daily irrigation from 0.5” to 0.3” had no direct impact on either rose or hydrangea growth. The conventional substrate with 7% more water retention and 5% less air space increased rose and hydrangea crop shoot growth by 8% and 18%, respectively, most likely due to increased water and nutrient availability and subsequent decreased crop stress. The 25% reduction in CRF incorporated in the top half of the substrate decreased rose and hydrangea growth on average 14% and 35%, respectively, when compared to a 1.00x rate of CRF applied as either a top-dress or incorporated throughout the container profile. Future research is needed to look at substrate and fertilizer rate interactions under varying irrigation regimes for high and low feeder crops to identify additional opportunities to conserve resources and possibly increase nursery crop profitability.

Technical Abstract: Current best management practices for containerized nursery crops maximize plant growth while minimizing nutrient leaching. Therefore, this study tested how plant growth was affected by reducing the industry standard rate of fertilizer when grown in two soilless substrates with different physical properties under two irrigation levels. Controlled-release fertilizer (CRF) treatments included 1.0x (45g) applied as topdress (TD), 1.0x (45g) incorporated throughout (IT) the container, or 0.75x (34g) incorporated into only the top half (TH) of the container. Rosa ‘BAIneon’ Screaming Neon Red™ rose and Hydrangea macrophylla ‘PIIHM-II’ Endless Summer® Bloomstruck® hydrangea were potted using Aeration+ Potting Mix (AS40) or All-purpose Potting Mix (PM2) substrates. Plants received high and low irrigation levels for 18 weeks. Final dry weight (DW) was most affected by fertilizer, to a lesser extent substrate, and not at all by the two irrigation volumes. Regardless of taxa, the largest DWs were produced when receiving mineral nutrients via IT or TD treatments when compared to TH and grown in PM2. Electrical conductivity (EC) was greatest in the PM2 substrate with a 1.0x CRF rate, regardless if IT or TD. Both taxa were unsaleable in the TH treatment, thus negating the environmental benefit achieved by a reduction in leaching.