Majallah-i ̒Ulum-i Bāghbānī (Jul 2016)
The Effect of Phosphorus and Zinc Fertilizers on Nutrient Content and Essential Oil Yield of German Chamomile under Drought Stress (Matricaria recutita L.)
Abstract
Introduction: The German chamomile (Matricaria recutita L.) is mainly cultivated for essential oil. Nowadays, it is a highly favored and much-used medicinal plant in reqular and traditional medicine. Water deficit is one of the most important limiting factors on crops production in arid and semi-arid regions (Sharafi et al. 2002). Drought stress limits the growth of plants by reducing water content of tissues and causes some metabolic and physiological changes. On the other hand, the availability of nutrients in the soil is affected by drought stress. Thus, nutritional management of plants under drought stress conditions is one of the most important factors in crop production. A better understanding of the role of nutrients in plant resistance to drought is associated with improvement of fertilizer management in arid and semi-arid areas. Our objectives were to investigate the effects of phosphorus and zinc fertilizers on nutrient content and essential oil yield of German chamomile under drought stress. Material and Methods: The experiment was conducted in split plot factorial based on randomized complete block design with three replications at Research farm of University of Zabol in 2013. Drought stress consisted of three levels 75% (control), 50% (mild stress) and 25% of field capacity (severe stress) as main plots, and factorial combinations of three triple superphosphate fertilizer (CaH4P2O8) levels (0, 150, and 300 kg ha-1) and two zinc sulphate fertilizer (ZnSO4H2O) levels (0 and 30 kg ha-1) as sub plots (the fertilizers were applied before planting time). The seeds were sown at 20 cm apart in rows 40 cm wide, on first half of March 2013. Drought stress levels were determined by the Time Domain Reflectometry (TDR). The success of chamomile cultivation as a commercial venture lies in how efficiently and effectively one can collect the flowers at the right stage during the peak flowering season extending over a period of 3–6 weeks. So, flowers were selectively collected on 27 April, 30 April, 4 May, 8 May, and 12 May 2013. German chamomile essential oil was extracted from the dried flowers and using Clevenger system. In the study, the content of potassium, sodium, zinc, phosphorus, chlorophyll a, chlorophyll b and essential oil yield were measured. Statistical analysis was carried out using SAS software (version 9.1). Significant difference was set at P ≤ 0.05 and determined using the Duncan's multiple-range test. Results and Discussion: The results showed that exposing chamomile plants to soil moisture stress during its life cycle might lead to a significant effect on essential oil yield and the nutrient content except zinc and phosphorus. The phosphorus fertilizer also affected the content of potassium, sodium, zinc, phosphorus, chlorophyll and essential oil yield while the zinc fertilizer just affected zinc and phosphorus content, chlorophyll b and essential oil yield significantly. Also, we observed that high application of phosphorus fertilizer (300 kg ha-1) had a negative effect on yield of chamomile. This plant growth disorder is maybe because of interaction between P and Zn that is usually termed ‘P-induced-Zn deficiency’. This disorder in plant growth is associated with high levels of available P or with application of P to soil. Thus, it is important that the application of nutrients to be in balance. Having a good nutrient balance is therefore an important factor to improve plant growth by indicating the actual amount and the combination of nutrients that the production needs. Also, this is a good way to save money. In summary, the results of this study indicated that drought stress caused significant effects on physiological traits, essential oil yield and nutrient content. The results showed that optimum amount of Zn and P can improve the studied traits of chamomile. According to the results of this experiment, it seems that the application of Zn under drought stress condition can decrease damage of drought stress that this is maybe because of the critical role of that in plant nutrition and production. Conclusion: In general, the results suggested that irrigation based on 50% of field capacity with application of 150 kg phosphorus fertilizer ha-1 and 30 kg zinc fertilizer ha-1 can improve essential oil yield and medicine components of German chamomile essential oil.
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