Introduction: Quinoa, a pseudocereal renowned for its exceptional nutritional profile, has garnered significant global attention in recent years due to its high-quality protein, balanced essential amino acids, dietary fiber, and rich micronutrient content. Recognized for its resilience, quinoa can be cultivated in marginal soils and exhibits considerable tolerance to abiotic stresses such as drought and salinity, making it a promising candidate for agricultural systems facing water scarcity. In the context of climate change and the increasing frequency and intensity of drought events in Iran, particularly in Mazandaran province, the introduction and expansion of drought-tolerant crops like quinoa have become imperative. Within this framework, determining the optimal sowing date emerges as a critical agronomic management factor, profoundly influencing successful crop establishment, yield enhancement, and overall resource use efficiency. The primary objective of this research was to identify the most favorable sowing date for a specific quinoa cultivar under the climatic and soil conditions of Galugah county, Mazandaran province, with a specific focus on phenological traits, yield components, and growth indices.
Materials and methods: This study was conducted as a field experiment arranged in a Randomized Complete Block Design with three replications, over two consecutive growing seasons (2019-2020 and 2020-2021) at a research field in Galugah county, eastern Mazandaran province. The experimental treatments consisted of nine sowing dates at 30-day intervals, including: January 6, 2020; February 7, 2020; May 6, 2020; August 19, 2020; September 5, 2020; February 3, 2021; March 8, 2021; May 5, 2021; and September 9, 2021. Throughout the growth cycle, data pertaining to key phenological stages were meticulously recorded, including: days to emergence, days to the four-leaf stage, days to initial flowering, days to panicle color change, and days to physiological maturity and harvest. Furthermore, traits associated with yield and its components—such as grain yield, biological yield, harvest index, 1000-seed weight, number of secondary panicles, and length of the main panicle—were measured and assessed. Combined analysis of variance for the collected data was performed using SAS statistical software version 9.4, and mean comparisons were carried out using the LSD test at the 5% probability level to determine significant differences among treatment means. The results indicated that sowing date had a significant effect on all evaluated traits.
Results: The results of the analysis of variance revealed that the effect of sowing date was highly significant (p ≤ 0.01) on all measured phenological, morphological, and growth-related traits. The longest total growth period (137 days) was associated with the sowing date of January 5, whereas the shortest growth cycle (70 days) was recorded for the sowing date of May 4. The maximum grain filling rate (27.91 g m⁻² day⁻¹) was observed for the August 5 sowing date, while the minimum rate for this parameter was noted in the spring-sown treatments. Additionally, the highest number of secondary panicles and the greatest length of the main panicle were recorded for the treatments sown in late summer, indicative of the positive influence of the environmental conditions prevalent during this period on the development of the plant's reproductive structures. The findings of this investigation demonstrated a significant positive correlation between plant height and main panicle length, suggesting the influential role of robust vegetative growth in supporting the development of reproductive organs. Thousand-seed weight also exhibited significant positive correlations with grain yield, biological yield, and harvest index; however, a negative correlation was observed with the number of secondary panicles. These outcomes suggest that late-summer sowing (September) provides optimal temperature, moisture, and photoperiod conditions, thereby enhancing photosynthetic efficiency, promoting the efficient allocation of photoassimilates, and ultimately leading to increased grain yield and a higher harvest index. Conversely, sowing in spring and early summer resulted in a significant decline in both quantitative and qualitative traits under study, primarily attributable to the synchronization of sensitive growth stages with periods of heat stress and water deficit, which adversely affect plant metabolism and development.
Conclusion: The results of this study demonstrate that the selection of an appropriate sowing date (late summer) for quinoa cultivation in the Galugah region of Mazandaran province, by modulating phenological stages and facilitating the optimal partitioning of photosynthetic assimilates, significantly improves grain yield, enhances the harvest index, and promotes the favorable development of yield components. In contrast, sowing during spring and early summer, due to exposure to concurrent environmental stresses, leads to a substantial reduction in yield and its associated components. Therefore, it is strongly recommended that local farmers in the region adopt late-summer sowing practices to realize the full production potential of quinoa and achieve sustainable agricultural productivity under the prevailing and future climatic scenarios of the area. |
