Greenhouse pot study finds Azolla and Moringa extracts improve geranium growth and essential oil output in sandy soil

A controlled greenhouse pot study of geranium (Pelargonium graveolens L.) found that weekly aqueous applications of Azolla or Moringa extract through irrigation water improved growth, physiological measures, nutrient uptake and essential oil production in sandy soil. The 10% Moringa treatment produced the largest responses relative to the untreated control, including 2.5- to 2.6-fold greater plant height and increases of 1.4- to 2.3-fold in essential oil yield across the two growing seasons.

The study was conducted over the 2023 and 2024 growing seasons at the Central Laboratory for Agricultural Climate of the Agricultural Research Center in Giza Governorate, Egypt. Uniform geranium seedlings were planted in plastic pots in sandy soil during the first week of March, thinned to three plants per pot after 45 days and maintained in a greenhouse. Plants were harvested twice in each season, at 90 and 180 days after planting, with the second harvest recording higher values for most growth and yield measures.

Five treatments were evaluated in a completely randomized design with four replicates per treatment. The control received a complete Hoagland nutrient solution, while the other treatments received weekly applications through irrigation water of Azolla extract at 50% or 75%, or Moringa leaf extract at 5% or 10%. Each replicate consisted of eight pots with three plants per pot. Fresh Azolla extract was prepared by boiling washed biomass in distilled water, whereas fresh Moringa extract was produced by blending leaves with distilled water, filtering the mixture and centrifuging it at 8,000 × g for 15 minutes.

Both plant-based extracts significantly enhanced vegetative growth relative to the control, with 10% Moringa producing the highest values. In the second harvest, plants receiving this treatment reached 114.5 cm in the first season and 119.6 cm in the second, compared with fold increases of 2.5 and 2.6. Branch numbers increased by 2.1- to 2.3-fold, fresh biomass by 2.0- to 2.1-fold and dry biomass by 2.0- to 2.1-fold. Treatment and harvest effects on the growth variables were generally significant at P ≤ 0.001, although some treatment-by-harvest interactions were not significant.

Photosynthetic pigments also increased under extract application. With 10% Moringa at the second harvest, chlorophyll a reached 0.8 and 0.9 mg g−1 fresh weight, chlorophyll b reached 0.4 and 0.5 mg g−1, and carotenoids reached 0.6 mg g−1 in the two seasons. Compared with the control, the treatment was associated with 1.7-fold higher chlorophyll a, 2-fold higher chlorophyll b and 1- to 1.3-fold higher carotenoids. The treatment and harvest effects were significant for chlorophyll a at P ≤ 0.001, for chlorophyll b at P ≤ 0.05 and for carotenoids at P ≤ 0.01, without significant treatment-by-harvest interactions for these pigments.

Essential oil content was higher at the first harvest, but essential oil yield per plant was greater at the second harvest. The highest oil yield under 10% Moringa was 1.4 g per plant in the first season and 1.7 g per plant in the second, representing increases of 1.4- to 2.3-fold relative to the control; oil content rose by 1.1- to 1.4-fold. Gas chromatographic analyses identified citronellol, geraniol and α-gurjunene as major constituents, with oxygenated monoterpenes forming the dominant chemical group. Under 10% Moringa at the second harvest, citronellol reached 774.2 mg per plant, geraniol was associated with a 3.3-fold increase over the control, α-gurjunene increased 2.7-fold and total oxygenated monoterpenes increased 2.3-fold.

Leaf chemical measures generally rose with extract treatment and were higher at the second harvest. At the second harvest with 10% Moringa, total phenolics reached 16.6 and 19.3 mg g−1 dry weight in the two seasons, 1.5- and 1.6-fold above control values. Flavonoids increased by 1.6- to 1.9-fold, while free-radical scavenging inhibition reached 62.34% and 60.2%, representing 1.7- and 1.8-fold increases. Total carbohydrate content was reported as 1.3-fold higher than the control, and crude protein content increased by 1.5-fold in the first season and 1.8-fold in the second.

The treatments also increased plant-tissue concentrations and total uptake of nitrogen, phosphorus and potassium. With 10% Moringa at the second harvest, nitrogen uptake reached 3.6 and 3.7 g per plant in the two seasons, compared with fold increases of 3.1- to 3.6-fold over control. Potassium uptake increased by 2.9- to 3.3-fold, while phosphorus uptake was reported as 5- to 25-fold higher. Because larger nutrient uptake figures reflect both tissue concentrations and total biomass, these values cannot be interpreted independently of the observed increase in plant growth.

The authors proposed that the extracts improved geranium performance through effects on nutrition, photosynthetic activity and secondary metabolism, while successive cutting stimulated regrowth and altered physiological and biochemical processes. They also cautioned that larger-scale field and economic studies are needed to establish commercial feasibility, and that the industrial applicability of the changes in essential oil composition requires further research. The findings therefore come from a greenhouse experiment using potted plants over two seasons, rather than from an open-field trial or commercial production assessment, and the tested extract concentrations should not be assumed to produce the same results under field conditions.

Subject of Research: Effects of Azolla and Moringa extracts on geranium growth, physiology, nutrients and essential oil production in sandy soil

Article Title: Response of geranium to soil applications of Azolla and Moringa extracts: effects on growth, essential oil and physiological parameters

Article References: Abd-Rabbu, H. S., Aboud, F. S., & Khalid, K. A. (2026). Response of geranium to soil applications of Azolla and Moringa extracts: effects on growth, essential oil and physiological parameters. BMC Plant Biology, 26(1), Article 1623. https://doi.org/10.1186/s12870-026-09900-0

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09900-0

Keywords: geranium, Azolla, Moringa, sandy soil, biostimulants, essential oil, plant growth, nutrient uptake, greenhouse study, Response, soil, applications