Growth, chemical, and biochemical composition of Conocarpus erectus L. in response to NPK fertilizers and extracts of active dry yeast, seaweeds, and green tea

El_Sayed El_Mahrouk^1*Huda Gamal Mahmoud¹Prof Dr.Khaled Abdelaal²Hayam Mohamed³Ahmed Eltarawy¹Waleed Alsaqqaf⁴HAYSSAM M. Ali^4*

• ¹Horticulture Department, Faculty of Agriculture, Kafrelsheikh University, Egypt, Kafrelsheikh, Egypt
• ²Department of Agricultural Botany, Faculty of Agriculture, Kafrelsheikh University, Kafr Elsheikh, Kafr el-Sheikh, Egypt
• ³3. Agricultural Research Center (ARC), Horticulture Research Institute Alex. Branch (Antoniadis), Alexandria, Egypt, Alex,, Egypt
• ⁴Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia

Conocarpus erectus L. is an ornamental shrub or tree commonly used in landscapes such as gardens, cities, and roadsides. Fertilization plays a vital role in enhancing its aesthetic and growth characteristics. A pot experiment was conducted using a randomized complete split-plot design during the 2022 and 2023 seasons to evaluate the effects of NPK fertilizers at 100%, 75%, and 50% of the recommended doses (18 g ammonium sulfate, 12 g calcium superphosphate, and 6 g potassium sulfate per plant), as well as natural extracts including active dry yeast (ADY) at 1 or 3 g L⁻¹, green tea (GT) at 0.2 or 0.5 g L⁻¹, and seaweed extract (SW) at 1 or 1.5 mL L⁻¹, applied individually and in combinations. The results showed that the 100% NPK dose significantly enhanced plant height, branch number, stem diameter, leaf area, chlorophyll index, fresh and dry weights of shoots and roots, relative water content (in the second season), and N, P, K, and carbohydrate contents compared to the 75% and 50% doses in both seasons. Additionally, it increased peroxidase activity, phenolic compounds, and antioxidant activity. Interestingly, the 75% NPK treatment caused higher relative water content (in the first season), catalase, and polyphenol oxidase (PPO) activities than the other treatments. All natural extract treatments improved studied traits over the untreated control. Among them, 3 g L⁻¹ ADY was the most effective for most traits, while SW at 1.5 mL L⁻¹ improved leaf area and the combined treatment of 1 g L⁻¹ ADY + 0.2 g L⁻¹ GT + 1 mL L⁻¹ SW resulted in the highest P%. The best overall results were obtained with the combination of 100% NPK and 3 g L⁻¹ ADY, except stem diameter, P%, and PPO activity, which peaked with 100% NPK + 1.5 mL L⁻¹ SW, the triple mix of ADY+GT+SW, and 75% NPK + 3 g L⁻¹ ADY, respectively. Thus, the combination of 100% NPK and 3 g L⁻¹ ADY is recommended to optimize growth and reduce overuse of chemical fertilizers and minimizing environmental contamination.