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The current study investigates the effects of humic acid concentration, its application methods as well as nitrogen ratios on the morphological, yield and biochemical characteristics of strawberry cv. Paros, during 2014–2015 in Ardabil Province, Iran. The study has been conducted within the framework of a double split plot randomized complete block design with three replications and density of 10 plants per replications. Different nitrogen levels (50, 100 and 150 kg ha−1) were examined in the main plots while application methods of humic acid (foliar and soil) and its different concentrations (0, 2, 4 and 6 kg ha−1) were considered in the subplots and sub-sub plots, respectively. The results of the analysis of variance (ANOVA) indicated that the interaction effects of different concentrations of nitrogen, humic acid and its application methods are significant on most of the measured variables at 5% probability level. Mean comparisons showed that the highest values for the leaf area, fruit yield, chlorophyll a, carotenoids and titratable acidity are associated with the combined treatments of nitrogen and humic acid with concentrations of 100 kg ha−1 and 4 kg ha−1, respectively. In three-way interactions, the highest shoot and root biomass and total chlorophyll content were obtained from the application of 100 kg ha−1nitrogen and 4 kg ha−1 foliar humic acid, while the highest nitrogen and protein contents of leaf and root were achieved upon applying 2 kg ha−1 foliar humic acid and 150 kg ha−1 nitrogen. Moreover, the highest amounts of ascorbic acid and total soluble solids were found at a concentration level of 100 kg ha−1 nitrogen along with applying 2 and 6 kg ha−1 foliar and soil humic acids, respectively. Finally, the best results of most of the studied traits were observed at 100 kg ha−1 nitrogen and 4 kg ha−1 foliar humic acid application. [ABSTRACT FROM AUTHOR]

• Three independent experiments on peach and nectarine cultivars and genotypes in Iran showed significant variations in growth, yield, and biochemical behaviors. • 'Henri' was found to have superior yield, tissue firmness, and total soluble solids. • Specific cultivars were found to have higher yield efficiency and nutrient levels compared to control cultivars, and the study recommends 'Flamino', 'Nectared', and 'Henri' as the best nectarine cultivars and 'Shasta', 'Sorkho-Sefid Mashhad', 'Suncrest', 'Fayette', and 'Shandabad-Hasteh-Joda' peaches as superior cultivars for specific locations. • These findings emphasize the importance of selecting appropriate cultivars for optimal growth and yield and continued research in stone fruit breeding. Stone fruit breeders face a significant challenge in obtaining new and high-yielding cultivars, and utilizing unknown ones. Among stone fruit, peaches and nectarines are the most prominent fruits. To address this issue, three independent experiments were conducted on various peach and nectarine cultivars and genotypes at two locations in Iran during 2018–2019 and 2019–2020 using a randomized complete block design with three replications. The results showed significant variations in growth, yield, and biochemical behaviors among the different genotypes and cultivars. 'Henri' was found to have superior yield, tissue firmness, and total soluble solids. Additionally, certain peach cultivars, such as 'Fayette', 'Sorkho-Sefid-Mashhad', and 'Shandabad', had higher yield efficiency than the control cultivar 'J.H. Hale'. Furthermore, 'PMsh-5′ had higher levels of ascorbic acid, antioxidant capacity, and carotenoids. 'Haj-Kazemi' had the tallest average tree height, trunk diameter, and crown of the tree in Golmakan, while 'Anjiri-Zaferani' had the highest levels of total soluble solids, flavor index, and pH. Based on these findings, 'Flamino', 'Nectared', and 'Henri' are recommended as the best nectarine cultivars in Mashhad due to their high pomological and phenological traits. 'Shasta', 'Sorkho-Sefid Mashhad', and 'Suncrest', as well as 'Fayette' and 'Shandabad-Hasteh-Joda' peaches, are recommended as superior cultivars for Mashhad and Golmakan, respectively. This study highlights the importance of selecting appropriate cultivars for optimal growth and yield and emphasizes the need for further research in stone fruit breeding. [ABSTRACT FROM AUTHOR]