Composted Green Waste as a Peat Substitute in Growing Media for Vinca (Catharanthus roseus (L.) G. Don) and Zinnia (Zinnia elegans Jacq.)

The purpose of this work was to explore the feasibility of replacing all or part of peat with composted green waste (CGW) for vinca (Catharanthus roseus (L.) G. Don) and zinnia (Zinnia elegans Jacq.) cultivation. Seven different growing media were prepared as follows (volume/volume): T1, 100% CGW; T2, 80% CGW + 20% peat; T3, 60% CGW + 40% peat; T4, 50% CGW + 50% peat; T5, 40% CGW + 60% peat; T6, 20% CGW + 80% peat; and T7, 100% peat. In the course of the experiment, the physicochemical properties of the seven media were analyzed, and the growth of vinca and zinnia was determined. Studies showed that replacing peat completely or partially with CGW could significantly enhance the nutrient content, bulk density, water-holding capacity, total porosity, aeration porosity, water-holding porosity, organic matter, pH, and electrical conductivity of growing media. In comparison with what observed with T7 (control), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), plant height (HP), root length (RL), flower number (FN), total chlorophyll, and the content of chlorophyll a, chlorophyll b, and carotenoids in the leaves of vinca cultivated under T5 conditions increased by 36%, 34%, 84%, 27%, 34%, 25%, 157%, 62%, 60%, and 33%, respectively; SFW, SDW, RFW, RDW, HP, RL, FN, total chlorophylls, and the content of chlorophyll a, chlorophyll b, and carotenoids in the leaves of zinnia increased by 341%, 296%, 365%, 302%, 206%, 93%, 180%, 56%, 49%, 67%, 110%, respectively.