| چکیده انگلیسی مقاله |
Background and objectives: Significant efforts are made during the early establishment and growth stages of seedlings to enhance their resistance to environmental stresses, thereby increasing the success of afforestation projects. One of the research goals is to extend irrigation periods and reduce associated costs. In recent years, afforestation projects have experienced considerable growth, driven by the importance of environmental, economic, and social factors, and cutting-edge technologies are utilized in this field. Various methods, such as the use of superabsorbent treatments and Herbam mineral fertilizer, have been tested to mitigate the negative effects of drought stress. This study aims to evaluate the impact of superabsorbent treatments and Herbam mineral fertilizer on the drought resistance of one-year-old bitter olive seedlings.
Methodology: One-year-old bitter olive seedlings were obtained from the Qareq Nursery in Golestan Province. A total of 1,000 seedlings were collected, and 360 seedlings with equal collar diameter, height, and root length were selected. The seedlings were planted in size seven pots (exact diameter: 23 cm and height: 21.5 cm) in mid-March. After applying the fertilizer and superabsorbent (0, 25, 50, and 75 grams), irrigation was carried out every five, ten, and fifteen days for 140 days. Subsequently, measurements were taken for various growth parameters including diameter growth, height growth, leaf count, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, leaf water potential, relative water content, leaf area, specific leaf area, leaf dry weight, length of the longest lateral root, fresh and dry biomass, and leaf nitrogen, phosphorus, and potassium. Data were compared using Duncan’s test at one and five percent statistical levels.
Results: Results showed that the maximum leaf area, using 50 grams of superabsorbent with a five-day irrigation interval, was 63.127 square centimeters, while the minimum was 68.958 square centimeters with the same amount of superabsorbent but a fifteen-day irrigation interval. The interaction effect of treatment levels and drought stress on chlorophylls, carotenoids, leaf dry weight, and relative water content was significant. The highest water potential was observed with 25 grams of superabsorbent under five-day irrigation conditions, while the lowest was with the same amount under fifteen-day irrigation conditions. Seedlings irrigated every five days with 75 grams of superabsorbent had the highest nitrogen and potassium content, while 25 grams of superabsorbent under fifteen-day irrigation conditions resulted in the highest phosphorus content. The interaction of treatment levels and drought stress significantly affected nitrogen, phosphorus, potassium, chlorophylls, carotenoids, leaf dry weight, and relative water content, but had no effect on other measured traits. Drought stress significantly impacted all traits, while different levels of superabsorbent only had a significant effect on the three measured elements, leaf area, specific leaf area, and leaf dry weight. The highest leaf dry weight and relative water content were observed with 50 and 25 grams of superabsorbent and five-day irrigation. Additionally, 50 grams of superabsorbent with ten-day irrigation produced the highest levels of chlorophylls and carotenoids. The highest nitrogen, phosphorus, and potassium were found with five-day irrigation and 75 grams of superabsorbent. Drought stress and different levels of superabsorbent did not affect seedling diameter but did affect height and leaf count. The greatest stem height was achieved under five-day irrigation with 50 and 75 grams of superabsorbent, twice that of the control height.
Conclusion: It can be generally stated that the use of superabsorbent and Herbam mineral fertilizer enhances moisture availability and strengthens the area around the root, thus providing better conditions for growth, especially under drought and water stress. Although further research over another growing season could provide more reliable recommendations, the positive effects of superabsorbent and Herbam mineral fertilizer on the establishment and strengthening of bitter olive seedlings suggest that these materials could be recommended for use in afforestation projects with this valuable species. |