Sensitivity of Hydrangea paniculata Plants to Residual Herbicides in Recycled Irrigation Varies with Plant Growth Stage

Abstract

Recycling irrigation return flow is a viable option to achieve sustainability in horticultural production systems, but residual herbicides present in recycled water may be phytotoxic. The sensitivity of plants to residual herbicides may vary depending on the growth stage of the plant. If sensitive growth stages are avoided, the risk associated with using recycled water can be reduced. Here, we quantified the effect of residual oryzalin and oxyfluorfen exposure at various growth stages of Hydrangea paniculata. Exposure to both herbicides reduced plant growth, leaf visual rating, soil plant analysis development (SPAD) chlorophyll index, net photosynthesis, and light-adapted fluorescence of H. paniculata. Herbicide injury was greater for plants exposed to herbicides at early growth stages, however, the recovery rate of those plants was also rapid. For oxyfluorfen, plants produced healthy new growth immediately after the end of exposure, but for oryzalin, even newly formed leaves developed herbicide injury after the end of exposure, therefore leaf damage continued to progress before recovering. However, damage caused by residual herbicide exposure at all growth stages recovered over time. Physiological measurements such as the SPAD index, net photosynthesis, and light-adapted fluorescence responded quickly to herbicides exposure hence provided an early indicator of herbicide damage and recovery.

High pH, Low Alkalinity Pond Water Used for Overhead Irrigation Does Not Affect Plant Growth of Select Flowering Shrubs1

“…m -2. s À1 (80 and 86 DAP or 49 and 77 DAT), indicating that treatment differences in the present study might have been recorded had physiology measurements been collected before plants matured in size. For example, exposure to residual herbicides in irrigation water reduced growth and physiology in newly expanded leaves of Hydrangea paniculata; however, when exposure ceased, plants recovered quickly from damage (Poudyal et al 2020). The robustness of popular genera grown in ornamental horticulture to overcome minor setbacks in gas exchange and growth seem to outweigh any reductions perceived in the present study.…”