Effect of different irrigation regimes and bio-fertilizers on grain yield, essential oil content, some physiologic traits and uptake of nutrient status in cumin (Cuminum cyminum L.)

Introduction Since medicinal plants in natural areas spread within the broad geographic limitations and collection and access to them is not cost-effective and on the other hand, the use of natural habitats will not be enough for the pharmacy industry, therefore, it is necessary to grow these plants in agricultural areas. In this regard, the choice of the landraces and suitable cultivars and nutrition and irrigation management, play an important role in increasing the quantity and quality of medicinal plants and reduce the negative effects of various environmental stresses on plants. Water deficit stress, permanent or temporary, limits the growth and the distribution of natural vegetation and the performance of cultivated plants more than any other environmental factor. Water stress have altered plants ‘metabolism significantly, thereby attenuating the growth, photosynthesis, and ultimately yield of the plants. Accordingly, it is very important to identify the mechanisms through the plant adapts to various conditions and resists against stresses, and to understand possible ways to address such stresses. In addition, under such conditions, drought management is an essential necessity. Cultivating plants with lower water requirements is a solution for effective management of available water resources. Being largely adaptable to a wide spectrum of various weather conditions, cumin serve as an economically efficient product in terms of water scarcity. Furthermore, in order to effectively manage water consumption in agriculture, adoption of various farming techniques, such as application of organic fertilizers or improving biological conditions of soil may render effective for reducing the impacts of water stress, while less use of chemical fertilizers may add to agricultural sustainability and health of medicinal plant. Materials and methods In order to study the effects of water deficit stress and biofertilization on seed yield, essential oil percentage and essential oil yield of green cumin, a split plot experiment was laid out in a randomized complete block design with three replications in the Alborz research station field in 2015 and 2016. Main factor included of irrigation with 60, 110 and 160 mm evaporation from pan and sub factor consisted of four biological fertilization (control, nitroxin fertilizer, biological phosphorus and nitroxin with biological phosphorus). In this experiment total chlorophyll (chl a+b), chl a and b, relative water content, potassium, phosphorus and nitrogen content of grain, proline, essential oil percentage and essential oil yield and seed yield were measured. Findings The results showed whit increasing severity water deficit stress, decreased total chlorophyll (chl a+b), chl a and b, relative water content and potassium, phosphorus and nitrogen content of grain, while increasing proline and essential oil content. Biofertilizer increased the total chl, chl a and b content, seed yield, essential oil percentage and essential oil yield and potassium, phosphorus and nitrogen content of grain. The highest seed yield were provided by nitroxin with biological phosphorus application (474.22 kg ha-1). Also, the interaction effect of biofertilizer and irrigation regime were significant on total chl, chl a and b, proline, potassium and phosphorus content of grain, so that the highest total chl, chl a and b content and potassium in seed were obtained in irrigation with 60 mm evaporation from pan and nitroxin whit bio- phosphorus application treatment. Conclusion Overall, the results showed that the use of nitroxin and bio- phosphorus fertilizer could improve essential oil percentage and essential oil yield (15.9% and 47%), seed yield (36.9%) and absorption of nitrogen (3.8%), phosphorus (21.9%) and potassium (10.4%) seeds in green cumin. Finally, it can be concluded that water deficet stress whit biofertilizers were suitable strategy for improve drug performance (essential oil percentage and essential oil yield) in green cumin and reducing environmental pollution. Keywords: Drought stress, nitoxin, bio- phosphorus, percentage and essential oil yield.