Effect of biological and chemical phosphorus fertilizers application on flower yield, essential oil percentage and osmatic adjustments of chamomile (Matricaria chamomilla L.) in response to water deficit stress

Application of chemical fertilizers besides contaminating the water and soil resources, and reducing the quality of agricultural and medicinal products has created serious environmental issues. Thus, to improve the soil fertility and for sustainable production, application of bio-fertilizers as an alternative to the chemical fertilizers have been widely promoted. Drought stress is an important environmental stress that reduces the growth and dry matter production of the medicinal plants, although increasing the effective ingredients production. This experiment was conducted to determine the most suitable amount of biological and chemical phosphorus fertilizers on dry flower yield, essential oil percentage, and osmotic adjustments of chamomile in response to water-deficit. The study was conducted at agricultural research institute of University of Zabol in 2016. The experiment was designed as a split plot using randomized complete blocks with three replicates. The main plots were different levels of water stress regulated by irrigation at 90, 70 and 50% of the field capacity (FC). The subplots were four levels of phosphorus fertilizers application including 100% chemical phosphorus fertilizer, 50% phosphate fertilizer and 50% bio-fertilizers (Phosphate B-2), 100% bio-fertilizer (Phosphate B-2), and the control plot without any fertilizer application. Properties such as flower yield, total leaf chlorophyll, soluble carbohydrate, essential oil percentage, proline, carotenoid, phosphorus (P) and potassium (K) were evaluated. After the data collection, SAS program was used for statistical analysis and means were separated according to the least significant difference (DMRT) at 0.05 level of probability. Results showed that K and soluble carbohydrate were affected by the water stress and phosphorus fertilizer application. Increasing the water stress intensity from 90% of FC (control) to 50% of FC reduced the K uptake and increased the soluble carbohydrate content. The combined application of chemical and biological fertilizers showed the most positive effects. Interaction of the water stress and phosphorus fertilizer application showed significant impacts on dry flower yield, essential oil percentage, proline, total leaf chlorophyll, carotenoids and P content. The highest dry flower yield, total leaf chlorophyll and P were obtained from the control plot and the treatment with integrated application of chemical and biological phosphorus fertilizers. The highest essential oil percentage, proline and carotenoids were obtained from the treatments with severe water stress and with combined application of chemical and biological phosphorus fertilizers. Results showed that the highest dry flower yield (420 kg.ha-1) was related to irrigation after 90% of FC along with the integrated application of chemical and biological phosphorus fertilizers and the highest essential oil percentage (0.846%) and proline (13.95 mg g-1FW) was belong to irrigation after 50% of FC along with integrated application of chemical and biological phosphorous fertilizer. According to these results, to improve the qualitative charactertics of chamomile medicinal plant, integrated application of chemical and biological fertilizer along with water stress would be appropriate.