Extended Abstract
Introduction
Date palm (Phoenix dactylifera L.) is one of the most important horticultural crops in Iran. According to the Agricultural Statistics Yearbook (2023), it ranks third in cultivated area and fifth in production among the country's horticultural crops. Beyond its contribution to employment and food security, date production represents an important component of Iran's non-oil agricultural economy. Pollination is an essential cultural practice in date palm cultivation, with pollination costs accounting for approximately 7% of growers' gross income. Mechanization of this operation has the potential to reduce pollination costs by more than 52%, corresponding to approximately 3.5% of total farm income.
The successful implementation of mechanized pollination depends largely on the availability of efficient pollination equipment and application methods. Dry pollen application has been investigated for more than six decades as a cost-effective mechanized alternative to conventional hand pollination, leading to the development of various pollination devices. More recently, mechanized spray pollination using pollen suspensions has attracted increasing attention in fruit crops such as kiwifruit and pistachio because it reduces pollen loss and prolongs pollen retention on receptive flowers. These advantages suggest that pollen suspension may provide a practical alternative for date palm pollination. Therefore, the present study evaluated the feasibility of mechanized spray pollination using pollen suspension in two commercially important date palm cultivars, Saomrun and Barhee.
Materials and Methods
The feasibility of mechanized spray pollination was evaluated over two consecutive growing seasons using Saomrun and Barhee date palms grown at the Om-Altomer Research Station in Khuzestan Province, Iran. The experiment was arranged in a completely randomized design with four treatments consisting of three pollen suspension concentrations (0.25, 0.50, and 1.00 g L⁻¹) and conventional hand pollination as the control, each replicated five times. Twenty palms of each cultivar were included in the experiment.
Pollen grains were collected from the male cultivar Ghannamy, processed, and stored according to the national technical guidelines for date palm pollination. A calibrated rechargeable backpack sprayer equipped with a conical nozzle was used to ensure uniform application of the pollen suspension.
Fruit set was determined by counting pollinated flowers and retained fruits on representative strands. Pollination efficiency was evaluated based on fruit set, parthenocarpic fruit formation, and fruit drop. Yield was determined as the average weight of four harvested bunches per palm. Data were analyzed using SAS software, and treatment means were compared using the least significant difference (LSD) test at the 5% probability level.
Results and Discussion
Analysis of variance showed that pollination treatments significantly affected fruit set, parthenocarpic fruit formation, fruit drop, and yield in both cultivars. For Saomrun, treatment effects were significant at the 1% probability level, whereas year had no significant effect on any measured trait.
In Saomrun, fruit set increased progressively with increasing pollen suspension concentration, reaching 45.79% at 1.00 g L⁻¹, although conventional hand pollination still produced the highest fruit set (55.8%). Similar trends were observed for yield, with the highest value among spray treatments (3.99 kg cluster⁻¹) obtained at 1.00 g L⁻¹, compared with 4.74 kg cluster⁻¹ under hand pollination. Parthenocarpic fruit formation remained low but differed significantly among treatments, whereas no parthenocarpic fruits were observed following conventional hand pollination. Fruit drop showed an inverse relationship with fruit set, being highest at the lowest pollen concentration and lowest under conventional hand pollination.
For Barhee, pollination treatment significantly affected fruit set, parthenocarpy, and yield at the 1% probability level and fruit drop at the 5% probability level. Unlike Saomrun, increasing pollen suspension concentration did not significantly improve fruit set, which remained substantially lower than that achieved with conventional hand pollination. The highest fruit set (50.59%) and yield (7.78 kg cluster⁻¹) were obtained in the control treatment. Parthenocarpic fruit formation was observed in all spray treatments but was absent in the control. Fruit drop decreased as pollen concentration increased, approaching the level observed under conventional hand pollination.
These findings confirm that adequate pollination is essential for profitable date production. The positive response of Saomrun to increasing pollen concentration is consistent with previous reports for other cultivars, including Lulu and Khenizi. In contrast, the weaker response of Barhee suggests that higher pollen concentrations or modifications to the spray application method may be required to achieve satisfactory pollination. Collectively, the results highlight the importance of optimizing pollen concentration and application techniques to improve the efficiency of mechanized spray pollination in commercial date production.
Conclusion
The two cultivars differed markedly in their response to mechanized spray pollination. Owing to its relatively low pollen requirement, Saomrun responded favorably to increasing pollen concentration, suggesting that concentrations of up to 2.0 g L⁻¹ should be evaluated in future studies. Under such conditions, spray pollination could serve as a practical backup method during periods of labor shortages or when unfavorable weather conditions disrupt the timely opening of female spathes.
In contrast, Barhee exhibited a higher pollen requirement and appeared more sensitive to factors affecting pollination success, including the relatively short receptive period of female flowers. Consequently, additional studies are needed to evaluate higher pollen concentrations together with different application timings and spraying strategies before mechanized spray pollination can be recommended for commercial production of this cultivar.
Overall, mechanized spray pollination using pollen suspension represents a promising alternative to conventional hand pollination for date palm. Further optimization of pollen concentration, carrier formulation, spray equipment, application timing, and spray volume will be essential for maximizing pollination efficiency and fruit yield under commercial production conditions.
Author Contributions
Conceptualization, A. Mostaan; Methodology, A. Mostaan; Project administration, A. Mostaan; Validation, A. Mostaan; writing, review, and final editing of the manuscript, A. Mostaan. Software, S. S. Marashi; Data curation, S. S. Marashi; Formal analysis, A. Mostaan; Writing the original draft of the manuscript, A. Mostaan.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
Acknowledgements
The authors thank Ms. Sara Ahmadizadeh and Mr. Seyed Naser Mousavi for their cooperation in the laboratory's affairs.
Ethical considerations
This work is not related to experimental animals or specific human diseases that requires publication and approval of publication ethics.
Conflict of interest
