Effects of Vermicompost on Growth Parameters, Water Use Efficiency and Quality of Zinnia Bedding Plants (Zinnia elegance ‘Dreamland Red’) under Different Irrigation Regimes

The drastic decline of precipitation over the past decade along with overuse of chemical inputs and consequent soil fertility reduction are the most important problems in the approach to agricultural expansion, particularly in urban landscaping. Therefore, an experiment was designed to examine the effects of different irrigation levels (40, 70 and 100 % of field capacity, or FC) and different vermicompost (VC) levels (0, 2.5 and 5 %) on the morphophysiological parameters of Zinnia elegance ‘Dreamland Red’ in a factorial experiment based on completely randomized design with three replications. Results indicated a significant reduction in root/shoot ratio, flower diameter, flower longevity, water use efficiency (WUE), photosynthetic pigments and nutrient uptake, along with reduction in the FC, while VC application improved these features. Based on the results, the highest electrolyte leakage and free radicals were observed in the 40 % of FC level without VC treatment, while the highest antiradical property and phenolic compounds were obtained at the same FC level along with 2.5% VC. Moreover, the highest WUE was observed at 2.5% VC with 70% FC, compared to 40% FC with no VC application. The flower diameter and longevity, as the most important indicators of the zinnias’ quality, were significantly affected by the interaction effects of irrigation and organic fertilizers.