Comparison of germination and seedling growth indices of Iranian Ox-Tongue (Echium amoenum) seeds resulting from the rootstock in different plant densities and in condition of organic and chemical fertilizers

Introduction: In recent years, the effect of exogenous organic amendments on soil properties and plant growth characteristics has received renewed attention (Motta and Maggiore, 2013). Although the utilization of mineral fertilizers could be viewed as the best solution in terms of plant productivity, this approach is often inefficient in the long-term in tropical ecosystems due to the limited ability of low-activity clay soils to retain nutrients. Intensive use of agrochemicals in agricultural systems is also known to have irreversible effects on soil and water resources (Weber et al, 2014). Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost can greatly enhance the physical structure of soil. Decomposing organic amendments slowly release nutrients which may be taken up by plants and thus result in improved agroecosystem productivity (Csizinszky, 2002). Vermicompost is currently being promoted to improve soil quality, reduces water and fertilizer needs and therefore increases the sustainability of agricultural practices in tropical countries. Vermicomposting is a process which stabilizes organic matter under aerobic and mesophilic conditions through the joint action of earthworms and microorganisms. The products of vermicomposting have been successfully used to suppress plant pests and disease as well as increase crop productivity (Sadeghi et al, 2014). Cow manure is an excellent fertilizer containing nitrogen, phosphorus, potassium and other nutrients. It also adds organic matter to the soil which may improve soil structure, aeration, soil moisture-holding capacity, and water infiltration (Motta and Maggiore, 2013). Plant density is the number of individuals of a given plants that occurs within a given sample unit or study area. Planting density can impact the overall health of plants. Plantings that are too sparse (the density is too low) may be more susceptible to weeds, while planting that are too dense might force plants to compete over scarce nutrients and water and cause stunted growth (Ibrahim, 2012). Evaluation of germination and biological characteristics of seed is the basic and primary studies in field of medicinal plants cultivation (Canter et al, 2005). Despite of many researches on the effect of organic fertilizers and plant density on different crops, information on the effects of these factors for seed resulting from rootstock of many medicinal plants is scarce, therefore, in this study germination and seedling growth indices of Echium amoenum seeds resulting from the rootstock in different plant densities and in condition of organic and chemical fertilizers was studied.

Materials and Methods:In order to evaluation of germinaton characteristics and seedling growth of Iranian Ox-Tongue (Echium amoenum) seeds resulting from the rootstock in different plant densities and in conditions of organic and chemical application, a factorial experiment based on CRD design with three replications was conducted in 2014 year, in Ferdowsi University of Mashhad, Iran. The experimental treatments included seeds resulting from treated Iraninan Ox-Tongue with different agronomic factors in farm including 3 plant densities (3, 5 and 10 plants per m2) and 4 different types of organic and chemical fertilizers (10 t.ha^-1 compost, 7 t.ha^-1 vermicompost, 30 t.ha^-1 cow manure, 90 kg.ha^-1 nitrogen chemical fertilizer and control).
Results and Discussion: The results showed that in all studied plant densities, the highest germination percentage obtained from vermicompost treatment. Germination rate in density of 5 plants per m² and application of compost, vermicompost, cow manure and chemical fertilizers was 6, 43, 49 and 40% more than the application of these fertilizers in density of 3 palnts per m2, respectively. The all studied organic fertilizers decreased the mean germination time compared to control, so that the mean germination time in compost, vermicompost and cow manure treatments decreased 58, 55 and 42% compared to control. The highest radicle and plumule length obtained in density of 5 plants per m2 and compost, vermicompost and chemical fertilizers increased radicle to plumule length ratio 3, 5 and 12% compared to control, respectively. Organic fertilizers are among the most significant resources for development of agricultural soil quality and increase in the yield of different medicinal plants. It has been reported that this ecological inputs provide favorable conditions for plant growth and development through improvement of physical, chemical and biological properties of the soil (Motta and Maggiore, 2013), therefore, it can be concluded that improvement of the most studied traits on germination characteristics of resulting seeds of Echium amoenum in the present study were due to use of organic fertilizers. Fallahi et al., (5) have reported the positive effects of organic fertilizers on the improvement of quantitative and qualitative characteristics in chamomile (Matricaria chamomilla L.). It seems plants compete with each other over scarce nutrients and water in high plant density and cause stunted growth (Ibrahim, 2012). In a study, effect of row spacing 20×40, 30×40 and 30×50 cm on yield and yield components of lemon balm (Melissa officinalis) reviewed and reported the related properties of seeds in treatment of 20×40 cm had the highest value (Saglam et al, 2004). Overall, according to the findings of this study, it seems that application of ecological inputs and use of optimum plant density in cultivation of Echium amoenum, can reduce the damage caused by the use of chemical fertilizers, meanwhile effective in improving the quality and properties of the resulting seeds.