Document Type : Research Article
Authors
1 Shahid Chamran university of Ahvaz
2 sahid chamran university of Ahvaz
Abstract
Introduction: Basil (Ocimum basilicum L.), is considered as one of the main edible crops of Lamiaceae family. In addition of consuming as a leafy vegetable, basil is known as a medicinal plant due to its aromatic and phytochemical compositions. The common edible basil has two main varieties i.e. Green and Opal. Although the production of this plant is highly happened in open farms during hot seasons, recent changes in agricultural policies in terms of year-round production, using less water and increasing the yield and quality, have encouraged the production of basil under controlled environments such as hydroponic systems. The main criteria to proceed a successful hydroponic culture are selecting proper cultivar, planting density and nutrition management. Optimum plant density alleviates the competition between plants and as a consequence, sufficient light and nutrient can lead to higher quantity and quality. This study aimed to discover the impact of plant density on the quality and yield properties of two main varieties of basil under hydroponics system.
Material and Methods: The experiment was done at Shahid Chamran University of Ahvaz during 2015-2016 growing season. A pot experiment was conducted based of Split-plot in time design with three replications. Cultivar (Green and Opal) and planting density (150, 200 and 250 plants per m2) were considered as the main and sub plot respectively. The plants were cut twice and different morphological and biochemical properties including number of leaves, leaf area, leafy parts yield, chlorophyll, carotenoids, soluble solid content, titrable acidity, total phenolic content, antioxidant capacity and essential oil content were analyzed.
Result and Discussion:The results showed that among applied treatments, the highest number of leaves (30.61), leaf area (26140 mm2) and stem fresh weight (3.28 g) were recorded for the var. Green with 150 p/m2 planting density at second cut. In contrast, this treatment had the lowest number of leaves (12.33) and leaf area (10810 mm2) at first cut. While maximum leaf fresh weight (5.84 g) was obtained for second cut of 150 p/m2 planting density, minimum leaf and stem fresh weight (3.09 and 2.01 g respectively) were found for second cut of 200 p/m2 planting density. Total fresh yield as an important criteria for a leafy vegetable was affected by both variety and planting density factors. The highest amount of yield (1427 g/m2) was recorded at second cut when plants were at 250 p/m2. In contrast, the plants of 150 p/m2 had the minimum yield at first cut (1020 g/m2). The chlorophyll content was higher in Opal variety surprisingly and the plants of 250 p/m2 and 150 p/m2 had around 2.09 mg/g chlorophyll at second cut. Similar findings were obtained for total phenolic content of leaves that was around 104.3 mg/Kg fresh weight for these treatments. Lowest levels of chlorophyll (1.29 mg/g FW) and total phenolic content (6.158 mg/kg) were seen in the leaves of var. Green when they were planted at 150 plant/m2 density. The data for total carotenoids content showed that the level of this pigments were affected by both parameters of variety and planting density. The leaves of var. Opal of 250 p/m2 density had the highest (6.252 mg/g fresh weight) carotenoids content. The highest (2.021 mmol Fe II/g FW) and lowest (0.69 mmol Fe II/g) amount of antioxidant capacity was recorded in Opal and Green varieties respectively, when they were at 150 plant/m2 density. The taste related parameters including total soluble solids, titrable acidity and essential oil content were not affected by planting density and variety. However, the level of acidity was increased by increasing plant density. On the other hand, a significant difference was seen in terms of TSS, acidity and essential oil between first and second cuts.
Conclusion: Overall and based on obtained data, it can be said that the var. Opal at 150 and 250 plants/m2 density showed the best results in terms of evaluated morphological and qualitative traits and can be recommended for hydroponics basil cultivation. Basil is harvest in 2-3 cuts and this experiment showed that for almost all vegetative parameters, the second cut had better results. The improved yield and quality at second cut could be attributed to the better establishment of roots and providing higher levels of nutrients.
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