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BACKGROUND: The strawberry is an important commercial crop, the improvement of its yield and quality is an imperative task. OBJECTIVE: The present research aimed to study the effect of colored netting and foliar application of amino acids on the physiological characteristics of strawberries subjected to different irrigation intervals. METHODS: The study was carried out as a factorial experiment based on a randomized complete block design with three factors including colored net at 4 levels (no netting, green, red, and yellow netting), organic acids at 4 levels (control, humic acid, glutamine, and arginine), and three levels of irrigation intervals (2, 4, and 6 days) in the greenhouse of Lahijan Agricultural Research Station, Iran. RESULTS: The results showed that the highest leaf number, shoot weight, chlorophyll and carotenoid content were related to yellow netting. The highest fruit yield, anthocyanins, and flavonoids were observed in the treatments of no-netting, green netting, and red netting, respectively. Data for the effect of organic acids showed that the glutamine-treated plants exhibited the highest yield, the humic acid-treated plants displayed the highest anthocyanin and carotenoid content, and the arginine-treated plants demonstrated the highest vitamin C content. The irrigation interval of 6 days caused to the lowest leaf number, flower and fruit number, shoot weight, fruit yield, and carotenoid content. Data for the trilateral effect of 'netting×organic acid×irrigation' showed that the highest flower number and fruit yield were obtained from 'green netting×glutamine×4 days', the highest anthocyanin content was obtained from 'green netting×humic acid×2 days', and the highest chlorophyll content was obtained from 'green netting×control×6 days'. The treatment of 'yellow netting×control×2 days' was related to the highest flavonoid content. CONCLUSIONS: The application of colored nets provides the strawberry with more optimal vegetative and reproductive growth. [ABSTRACT FROM AUTHOR]

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]