Enhancing Cauliflower Seedling Quality through Plug Tray Surface Covering and Root-zone Temperature Control

During tropical summers, plug tray root-zone temperatures often exceed 38 °C, impairing seedling development. We investigated a Tyvek ® plug surface covering and bottom cooling to improve the quality of cauliflower ( Brassica oleracea var. botrytis ) seedlings. A surface covering with 25 °C cooling reduced root-zone fluctuations from 14.5 to 8.0 °C, producing the highest seedling quality index (SQI) and Dickson quality index (DQI). Multispectral vegetation indices, particularly the modified simple ratio (mSR) and single-image normalized difference vegetation index (SI-NDVI), correlated strongly and negatively with the SQI ( r = –0.79, –0.69) and DQI ( r = –0.78, –0.67). A lower mSR and SI-NDVI corresponded with improved seedling quality, demonstrating their utility as nondestructive indicators of vigor. Surface covering and root-zone cooling can mitigate the thermal stress in tropical nurseries.