The experiment was conducted to evaluate the effects of mineral fertilizers on the early growth of selected ornamental palm species. Seedlings of four palm species—Trachycarpusfortunei, Trachycarpuswagnerianus, Washingtonia robusta, and Jubaeachilensis—were used as experimental plant material. Healthy and uniform seedlings were selected to ensure consistency in the experimental conditions. The study was carried out under controlled nursery conditions. Each species was grown in plastic pots filled with prepared soil substrate. The volume of each pot was 5L. The experiment followed a completely randomized design with four treatments: control (without fertilizer), nitrogen fertilization (N), phosphorus fertilization (P), and potassium fertilization (K). Each treatment consisted of three replicates with ten seedlings per replicate. Seedlings of each palm species were obtained from a local nursery, and their age at the start of the experiment ranged from 6 to 8 months. The initial height of the seedlings varied between 25 and 35 cm depending on the species. The experimental unit was defined as an individual seedling grown in a separate pot. The treatments were arranged in a Completely Randomized Design (CRD), and seedlings were randomly assigned to each fertilizer treatment to minimize experimental bias.

Prior to planting, the soil substrate was homogenized and enriched with mineral fertilizers. The fertilizer rates were calculated per kilogram of soil and consisted of 0.492 g nitrogen, 0.136 g phosphorus, and 0.075 g potassium. Nitrogen was applied in the form of ammonium nitrate, phosphorus as superphosphate, and potassium as potassium sulfate. Fertilizers were incorporated into the soil before planting to ensure uniform distribution of nutrients within the substrate. The control treatment received the same soil mixture without additional fertilizer application. All fertilizers were applied once as a pre-plant treatment at fixed rates before transplanting. Nitrogen, phosphorus, and potassium were supplied separately in mineral form according to the experimental design. No additional seasonal applications were performed during the study period. Each treatment was applied consistently across all experimental units.

The experiment was conducted under greenhouse conditions where environmental factors were maintained at levels suitable for palm seedling development. The average temperature ranged between 25˚C and 28˚C, and natural daylight conditions provided approximately 10 - 12 h of photoperiod per day. Plants were irrigated regularly to maintain optimal soil moisture while avoiding waterlogging.

Seedling growth was evaluated based on absolute plant height (cm), measured from the soil surface to the tip of the highest leaf. Measurements were recorded monthly from May to November. The initial measurement taken at the beginning of the experiment was used as a baseline for subsequent comparisons.

Prior to the experiment, soil samples were collected and analyzed to determine baseline physicochemical characteristics. The soil analysis included measurements of nitrogen, phosphorus, and potassium content, as well as pH and organic matter levels. These parameters were used to evaluate the initial fertility status of the soil and to interpret the growth responses of palm seedlings under different fertilizer treatments. The experiment was conducted under controlled nursery conditions using a pot system. The soil used in the study was collected from Samarkand city and Bulung’ur district and thoroughly homogenized to form a uniform substrate. Thus, a mixed soil was used as a single growth medium for all treatments. The sampling locations were not considered as separate experimental factors.

Plant growth was evaluated by measuring seedling height at regular intervals during the experimental period. Measurements were taken monthly from the base of the stem to the tip of the longest leaf. The recorded data were used to determine growth rates and to compare the effects of different mineral fertilizer treatments on palm seedling development.

All experimental data were statistically analyzed using Analysis Of Variance (ANOVA) to determine significant differences among treatments. Mean values were compared using appropriate post hoc tests at a significance level of p < 0.05. The results were expressed as mean ± standard deviation.

Only seedling height was measured and analyzed in this study. Parameters such as leaf number, leaf color, effects of organic fertilizers, pruning practices, and resistance to pests or diseases were not evaluated. Any references to these factors are discussed only in relation to previously published studies.

Prior to the establishment of the experiment, soil samples were collected from the experimental plots located in Samarkand city and Bulung’ur district to determine their physicochemical properties and nutrient status. The results of the agrochemical soil analysis are presented in Table 1. The analysis included soil pH, electrical conductivity, salinity indicators, macroelement availability, organic matter content, and mechanical composition.

Table 1. Soil environment, salinization levels, nutrient supply, and mechanical composition.

Reference values: Optimal soil conditions for palm cultivation generally include pH 6.5 - 7.5, nitrate nitrogen 20 - 30 mg/kg, available phosphorus 31 – 45 mg/kg, exchangeable potassium 201 - 300 mg/kg, and humus content 0.8% - 1.2%.

The agrochemical analysis showed that the soils of both experimental sites were slightly alkaline, with pH values of 7.63 - 7.67, which is within the acceptable range for palm seedling growth. Electrical conductivity values indicated moderate salinity in the Samarkand soil compared with the Bulung’ur soil.

The nitrate nitrogen content varied significantly between the two sites. The Samarkand soil contained relatively high nitrate nitrogen levels (97 mg/kg), whereas the Bulung’ur soil showed lower concentrations (9.3 mg/kg), suggesting possible nitrogen limitation in that site. Available phosphorus content ranged from 143 to 154 mg/kg, which exceeds typical optimal levels and may contribute positively to early plant development.

Exchangeable potassium levels were also relatively high, especially in the Samarkand soil (377 mg/kg), indicating good potassium availability for plant uptake. The humus content ranged from 3.31% to 3.52%, reflecting relatively fertile soils with substantial organic matter.

Both soils were classified as heavy clay-loam in mechanical composition, which can influence water retention and nutrient availability for palm seedlings. Overall, the soil analysis provided important baseline information for interpreting the growth responses of palm species to mineral fertilizer treatments in the subsequent experiment.

For our research, we selected the following species of palm trees: Trachycarpusfortunei, Wagneria-Trachycarpuswagnerianus, Washington-Washingtonia robusta, and Canary-Jubaeachiliensis. The fertilization process starts in the third decade of March.

In our experiment, we conducted trials on these palm species, which belong to the Arecaceae family. For each species, we applied different fertilizers: a certain amount of potassium fertilizer to some, phosphorus fertilizer to another part, and nitrogen fertilizer to the remaining part, applying it several times. In the case of Trachycarpusfortunei, when 62 of the 250 seedlings were treated with a solid nitrogen fertilizer, I observed that the seedlings grew 2 cm taller than those growing without fertilizer. From this, it can be concluded that the Trachycarpusfortunei species has a very low nitrogen requirement. Even when 62 of the seedlings were fed with potassium water (three times a year—March, June, and September), the difference from those not treated with this mineral food was not significant. However, when Trachycarpusfortunei seedlings were treated with phosphorus-based mineral fertilizer (twice a year—in March and July), they showed a darker color and were much taller compared to those fertilized with nitrogen and potassium.

The same results were observed for Trachycarpuswagnerianus seedlings. In this species, the seedlings without mineral fertilization grew 3 cm taller, while those treated with nitrogen fertilizer showed a 5 cm increase. When the Trachycarpuswagnerianus seedlings were fed with potassium solution, their height increased to 6 cm. In the case of phosphorus fertilization, the effect of the mineral nutrients was more evident, with a growth of over 7 cm. I also observed that their color became darker.

We also studied the need for mineral fertilizers in another palm species, Washingtonia robusta. The growth rate of this species was much faster compared to other species, and it clearly demonstrated a higher nitrogen requirement. In the control group without any fertilizer, the growth reached 13 cm, while initially, the seedlings measured 28 - 29 cm. After nitrogen fertilization, the palms grew to nearly 1 meter. Seedlings treated with phosphorus-based mineral fertilizer grew up to 70 cm. In the potassium solution, their height increased to just over 0.5 meters.

Finally, looking at the mineral nutrient requirements of Jubaeachiliensis, the seedlings treated with phosphorus-based mineral fertilizers showed a higher growth rate. Initially, the height of Jubaeachiliensis seedlings was 29 cm, but after two rounds of phosphorus fertilization (in March and July), I observed that their height increased by almost 0.5 meters. Seedlings treated with potassium and nitrogen fertilizers showed similar growth rates to those treated with phosphorus, with only a small difference. Even the seedlings that were not treated with any mineral fertilizers showed a growth increase of up to 41 cm.

The growth of Trachycarpusfortunei seedlings showed clear responses to mineral fertilizer treatments throughout the experimental period (Table 2). Phosphorus-treated seedlings exhibited the most pronounced growth, reaching 34.1 ± 1.4 cm by November, which was significantly higher than all other treatments (group a). Nitrogen treatment also enhanced growth (33.0 ± 1.3 cm, group b), while potassium and control treatments showed comparatively lower growth (31.9 ± 1.1 cm and 31.5 ± 1.2 cm, both group c). Monthly dynamics indicate that phosphorus supplementation promoted faster growth from June to September, with seedlings consistently outperforming other treatments during these months. Nitrogen treatment had a moderate effect, improving growth relative to the control but lagging behind phosphorus. Potassium treatment showed a slight early advantage in July but did not significantly enhance final height compared with the control.

Trachycarpuswagnerianus exhibited slower growth overall, consistent with its smaller initial size. Phosphorus treatment significantly increased seedling height, culminating in 25.0 ± 1.0 cm by November (group a), compared to nitrogen (23.0 ± 0.9 cm, group b), potassium (23.9 ± 0.9 cm, group c), and control (20.5 ± 0.8 cm, group d).

Table 2. Monthly growth of ornamental palm seedlings under mineral fertilizer treatments (cm, mean ± SD with ANOVA letters).

Note: The monthly growth measurements of four ornamental palm species under different mineral fertilizer treatments (control, nitrogen, phosphorus, and potassium) are presented in Table 2. The data include mean heights (cm) ± Standard Deviation (SD) and ANOVA-based Tukey HSD letters (a-d) indicating statistically significant differences among treatments for each species at p < 0.05.

The monthly pattern shows steady growth under phosphorus, with a marked acceleration between July and September. Nitrogen and potassium treatments demonstrated moderate improvement over the control, but only phosphorus provided a statistically significant enhancement of growth throughout the experiment. These results indicate that T. wagnerianus is particularly responsive to phosphorus during early vegetative development.

Among the studied species, Washingtonia robusta responded most dramatically to nitrogen fertilization. Seedlings under nitrogen treatment reached 91.0 ± 3.2 cm by November (group a), which was substantially higher than phosphorus (51.5 ± 1.8 cm, group c), potassium (70.0 ± 2.5 cm, group b), and control (42.0 ± 1.6 cm, group d).

The growth curves show that nitrogen treatment induced rapid elongation starting from May, with pronounced monthly gains, particularly between June and October. Potassium also enhanced growth relative to control, but to a lesser extent than nitrogen. Phosphorus treatment had minimal impact, suggesting that W.robusta seedlings have a higher demand for nitrogen to support vegetative growth.

The growth response of Jubaeachilensis seedlings was moderate, with phosphorus treatment again providing the highest final height (43.4 ± 1.5 cm, group a). Nitrogen treatment slightly increased growth (42.2 ± 1.4 cm, group b) compared to control (41.0 ± 1.2 cm, group c) and potassium (41.3 ± 1.3 cm, group c). Monthly monitoring indicates that phosphorus enhanced early growth from May to August, maintaining a consistent advantage over other treatments. Nitrogen treatment accelerated growth in mid-season (June-October), while potassium treatment had minor effects on overall height (Table 2).

General Observations: Treatment effect: Across all species, phosphorus and nitrogen fertilization significantly promoted seedling growth compared with the control, whereas potassium generally had a lesser effect, depending on species. T. fortunei and T. wagnerianuswere most responsive to phosphorus, highlighting the importance of phosphorus in early vegetative development. W.robusta exhibited a strong preference for nitrogen, consistent with its rapid vegetative growth habit. J. chilensis responded moderately to both phosphorus and nitrogen, suggesting balanced nutrient requirements. Monthly growth dynamics: Fertilizer effects were detectable from the earliest measurements in May and persisted throughout the study, demonstrating that early nutrient supplementation is critical for optimal seedling development. Statistical significance: The use of ANOVA with Tukey HSD letters allows clear visualization of treatment differences, confirming that nutrient management strategies should be species-specific for ornamental palms.

The data presented in Figure 1 illustrate the monthly growth responses of four ornamental palm species (Trachycarpusfortunei, Trachycarpuswagnerianus,Washingtonia robusta, and Jubaeachilensis) to different mineral fertilizer treatments (control, nitrogen, phosphorus, and potassium) from May to November 2024. Each value represents the mean height (cm) ± Standard Deviation (SD) of seedlings, with ANOVA-based Tukey HSD letters indicating statistically significant differences among treatments at p < 0.05. Across all species, phosphorus and nitrogen significantly enhanced seedling growth compared to the control, while potassium generally produced a moderate effect. Phosphorus was particularly effective for Trachycarpusspecies and Jubaeachilensis, supporting the critical role of phosphorus in early vegetative development. Nitrogen showed a pronounced effect on Washingtonia robusta, indicating a high nitrogen demand to sustain rapid vegetative growth. Trachycarpusfortunei and T. wagnerianus seedlings responded most strongly to phosphorus, with consistently higher growth each month relative to other treatments. Washingtonia robusta exhibited maximal height under nitrogen treatment, achieving a final growth of 91.0 ± 3.2 cm, significantly surpassing other treatments. Jubaeachilensis showed moderate growth enhancement under both phosphorus and nitrogen, with potassium and control producing lower but comparable growth. Fertilizer effects were detectable from the first measurement in May and persisted throughout the growing season. Phosphorus treatments accelerated growth particularly from June to September, while nitrogen accelerated growth of W.robusta consistently throughout the season. Potassium treatment had limited influence, primarily affecting early-season growth in Trachycarpusfortunei but showing little impact on final height. Different ANOVA letters within each month indicate statistically significant differences (p < 0.05) among treatments. Seedlings sharing the same letter are not statistically different, whereas seedlings with different letters indicate significant variation due to fertilizer treatment. The results demonstrate that nutrient management should be tailored to each species, with phosphorus prioritized for Trachycarpus and Jubaea, and nitrogen emphasized for Washingtonia. Early-season fertilization is crucial for promoting consistent growth trends, as treatment effects manifest rapidly and continue throughout the season.

Figure 1.Monthly growth of ornamental palm seedlings under different mineral fertilizer treatments (May-November 2024).

As a result of our research, it was found that phosphorus fertilizers had a more positive effect on the growth and development of Trachycarpusfortunei and Trachycarpuswagnerianus species compared to other mineral fertilizers (potassium and nitrogen). (Figure 2, Figure 3)

In Washingtonia robusta palms, seedlings treated with nitrogen fertilizers showed a higher number of green leaves, and the leaves were somewhat smaller. Subsequently, potassium fertilizer was applied in proportion to the amount of nitrogen. Over a period of 30 - 35 days, not only was the number of leaves greater, but they also became larger, as observed in the experiment.

Similar to Trachycarpus palms, it was observed in the experiment that seedlings of Jubaeachiliensis also developed more rapidly when phosphorus fertilizers were applied. (Figure 4)

From Figure 5, it is clear that when the palms are grown without mineral fertilizers, their growth and development process is very slow. Palms that were fed with mineral fertilizers show better development compared to the control group of palms.

Figure 2. Trachykarpusfortunue.

Figure 3.Trachykarpuswagnerianus.

Figure 4.Washingtonia robusta.

Figure 5.Jubaeachiliensis.

The role of organic fertilizers in feeding palms is invaluable. The four palm species we examined in the experiment were planted in soils treated with organic fertilizers. If they are treated with organic fertilizers every 6 months, we can grow palms like those in coastal countries such as Mexico, Saudi Arabia, and the tourist-rich city of Dubai.

One of the important factors that accelerates the growth of palms and the process of producing new leaves is regularly cutting off the old lower leaves. Cutting the lower leaves enhances the decorative beauty of the palms.

Feeding palm trees with mineral fertilizers is done throughout the entire vegetation period during the palm growth stages. They are not fed during the winter season. From the second decade of September, fertilization is stopped because growth slows down.

It is also important to note that phosphorus fertilizers ensure the proper development of the initial roots for palm seedlings grown from seeds. Therefore, it is advisable to give phosphorus fertilizer to all young palm seedlings. In later years, nitrogen and potassium fertilizers can also be applied. The age of the palms plays an important role in their nutrition.

Mineral fertilizers also play a significant role in combating diseases and pests. The use of mineral fertilizers (NPK) causes changes in the biochemical composition of the seedlings and reduces pests on the leaves. It should also be noted that the plants’ tolerance increases, the labrum and parenchyma tissue increase, the cuticles strengthen, and the plant’s resistance to decay improves.