The effect of water deficit, combined application of manure and chemical fertilizer on yield and some morpho-physiological characteristics of Arnica montana L.

Arnica montana L. is a rare plant under strict protection in several European countries and similar to medicinal plants has high commercial value. Water is one of the environmental factors which has a high impact on the growth and the essential oil content of medicinal plants. Plants are faced with various environmental stresses during their growing period. Each of these stresses has different effects on growth, metabolism, and yield according to the sensitivity level and stage of the plant growth. Management of nutrients consumption along with water consumption management influences the quantitative and qualitative yield of crops and medicinal plants. Manure is one of the organic fertilizer sources whose application in the sustainable management system of soil is conventional. In this regard, organic sources combined with chemical fertilizer can lead to soil fertility and increase crop production, because this system provides most of the plant's nutritional needs and increases the efficiency of nutrient absorption by the crop. This investigation was conducted to The effect of water deficit, combined application of manure and chemical fertilizer on yield, and some morpho-physiological characteristics of Arnica montana L.

A factorial experiment was carried out in a randomized complete block design with three replications at the research greenhouse, Zist Exsir kemia Company of Esfahan in 2019. The first factor was 5 levels of manure application: 1) no amended fertilizer, 2) 25 percent urea + 75 percent manure 3) 50 percent urea + 50 percent manure 4) 100 percent urea and 5) 100 percent manure, while 4 levels of irrigation regimes: 100 percent, 75 percent, 60 percent and 50 percent of water requirement were used as the second factor. The water need of the other treatments was considered based on the water demand of control with the TDR (Temperature Dependent Resistor) humidity meter. Harvesting of the flowers from each pot was done once a week till the full flowering stage and the number of flowers per plant, dry flower yield, harvest index of the flower, biological yield, proline, electrolyte leakage, stomatal conductance, total chlorophyll, nitrogen uptake efficiency, phenol, and flavonoid content was studied.

The results of the experiment showed that the effect of fertilizer, irrigation regimes, and their interaction was significant on all the characteristics. Means comparison of the interaction effect of fertilizer and irrigation regimes showed that the maximum number of flowers per plant, dry flower yield, and biological yield in 100 percent manure with 100 percent plant water requirement, the maximum harvest index of flower in control with 75 percent plant water requirement, the maximum electrolyte leakage in 100 percent manure with 60 percent plant water requirement, the maximum stomatal conductance in 100 percent manure with 100 percent plant water requirement, the maximum total chlorophyll in 100 percent urea with 100 percent plant water requirement and the maximum phenol, flavonoid and proline contents were derived in 100 percent urea with 50 percent plant water requirement were obtained.

Based on the results obtained in this experiment, it can be concluded that the 100 percent plant water requirement caused a reduction in proline, electrolyte leakage, phenol and flavonoid content, and improved plant growth condition in most of the fertilizer treatments. Moreover, the application of manure (especially at high stress levels) could reduce the effects of drought stress to some extent. So, according to the findings of this study, in order to obtain the maximum plant yield in similar conditions, the application of 100 percent manure with full irrigation is recommended.