Introduction
Thyme, a plant with valuable metabolites, has been using in the food, pharmaceutical and health industries due to its medicinal properties. Identifying the agricultural factors affecting the quantitative and qualitative changes of medicinal plants is crucial for increment quality and more production. The use of chemical fertilizers has been caused many environmental problems; therefore, it is important to use organic fertilizers in different density patterns of cultivation in order to reduce the consumption of chemical fertilizers to achieve sustainable agriculture.
 Materials and methods
This research was carried out as a split-plot design in the form of a randomized complete block design with two factors and three replications in rainfed conditions in the Mahidasht research station of Kermanshah province during the two crop years 2020-2021 and 2021-2022. The main factor included three levels (20 tons per hectare Caw manure, enriched straw at the rate of 10 tons per hectare and no fertilizer application) along with agricultural soil without applying fertilizer, and the sub factor was three densities (4, 6 and 8 plants per square meter). The three plants were randomly selected from each plot, plant height (cm), number of branches per plant, and canopy diameter (cm) were measured. In the flowering stage, plants of one square meter were harvested from each plot and the wet and dry weights were measured in grams per square meter. Also, the dry weight of leaves and stems was measured in grams per plant for each plot, which, leaf to stem ratio was calculated for each plot by dividing leaf to stem weight. The essential oil of 20 grams of dried leaves were extracted using a Clevenger apparatus, and the percentage of essential oil was determined for each plot, and finally, according to the dry leaf yield per square meter, the amount of essential oil yield of aerial parts of the plant per square meter was calculated.
 Results and Discussion
Analysis of variance showed that different fertilizers and different levels of density had a significant effect on all traits, but the interaction of fertilizer × density had a significant effect only on the traits of percentage and yield of essential oil. According to the mean comparison by Duncan's method, fertilizer increased the growth of thyme. All the vegetative characteristics of the plant were affected by the use of fertilizer. However, animal manure was the best among the two types of fertilizers used. On the other hand, with the increase in density, the plant height increased, but the number of branches in the plant and the canopy diameter showed a decreasing trend. in contrast to these two characteristics, the wet and dry yield of the plant was lower in low and high density than in medium density. A different trend was observed for the essential oil percentage and yield. The essential oil percentage increased by 17.53% by reducing the density from 8 plants to 4 plants. Interstingly, the yield of essential oil showed a decrease of 5.42%. The results of principal components analysis of the traits in different agricultural conditions showed that 94.3% of the variance was expressed based on the first two components, and the bi-plot of the two components confirmed the results of mean comparison.
 Conclusion
According to the final goal of this research, which was to determine the best density, in terms of using manure and enriched straw to achieve the desired result in the cultivation of rainfed thyme, therefore, based on the grouping of the two-factor interaction and principal components analysis, it was observed that the use of manure at the rate of 20 tons per hectare with density cultivation of 6 plants per square meter is the most suitable treatment for the cultivation of thyme in the rainfed conditions of Kermanshah province. Therefore, it can be recommended for the cultivation of this species in the rainy conditions of Kermanshah province.