3.1. Root colonization percentage
In both years, the highest root colonization percentage was measured in the 50:50 intercropping ratio with non-stressed plants (I20). Also, the lowest percentage of thyme root colonization (46.81% in the first year and 56.87% in the second year) was observed in the sole culture of thyme under severe stress (I80) (Fig. 2).
3.2. Dry yield
The highest and lowest dry yield (in both years) was achieved in the sole culture of thyme with well-watered condition (I20) and in the intercropping ratio of 66:34 with I80 water deficit (Fig. 3). Furthermore, in the first and second year, application of AMF enhanced the dry productivity by 17.3 and 14.5%, respectively, in comparison with control. However, the dry productivity in 50:50 and 66:44 intercrops decreased by 42 and 58% in the first year and by 38 and 59% in the second year, respectively, in comparison with thyme sole culture. Furthermore, the thyme dry yield in the moderate (I50) and severe water deficit (I80) decreased by 35 and 44% in the first year, and by 27 and 40% in the second year, respectively, in comparison with I20 (Table 4).
3.3. Nutrient concentrations
The most of macro- and micro nutrient concentrations was significantly impacted by single effects of water deficit levels, cropping patterns and AMF application. Also, interaction of water deficit levels × cropping patterns had a significant impact on Zn content (Table 5).
3.3.1. N concentration
In both years, the highest N concentration was calculated in 50:50 intercropping followed by 66:34. The lowest N concentration was recorded in the sole culture of thyme. The N content in 50:50 and 66:34 cropping patterns increased by 15 and 9% in the first year, and by 20 and 13% in the second year, respectively when compared with sole culture. Among three water deficit levels, the highest and lowest N content in both years was calculated in I20 and I80, respectively. Moreover, the N content in the first and second year enhanced by 10.9 and 9.6% after application of AMF (Table 5).
3.3.2. P concentration
The P content of thyme leaves in the first and second year enhanced by 10.5 and 8.7% after application of AMF. Also, the highest and lowest P concentration was recorded in I20 and I80 water deficit levels, respectively. The P content in the I50 and I80 water scarcity conditions decreased by 17 and 30% in first year and by 18 and 29% in the second year, respectively, when compared with well-watered conditions (Table 5).
3.3.3. K concentration
The maximum K content (15.2 and 17.1 g/kg in 2018 and 2019, respectively) was recorded in the intercropping ratio of 50:50 and 66:34. The content of K decreased by enhancing the water deficit levels. The maximum and minimum concentration of K in both years was achieved in I20 and I80, respectively. Overall, the K content in the first and second year increased by 14.1 and 13.2%, respectively, after application of AMF when compared with control (Table 5).
3.3.4. Ca concentration
The highest Ca content (4.4 and 5.3 g/kg in 2018 and 2019, respectively), was achieved in the intercropping ratio of 50:50. The concentration of Ca decreased under water deficit conditions. The maximum and minimum concentration of Ca in both years was achieved in I20 and I80 water deficits, respectively. The concentration of Ca in I20 was 14 and 30% (in the first year) and 14 and 23% (in the second year) higher than those registered in I50 and I80 treatments, respectively. Overall, the Ca concentration in the first and second year enhanced by 11.3 and 5.8%, respectively, after application of AMF in comparison with control (Table 5).
3.3.5. Mg concentration
The maximum Mg content in thyme leaves (2.6 and 3.4 g/kg in 2018 and 2019, respectively) was recorded in the intercropping ratio of 66:34 and 50:50, corresponding to an increase by 9 and 7% in the first year, and by 17 and 14% in the second year in comparison with sole culture. Also, the content of Mg decreased under water deficit conditions. The maximum and minimum content of Mg in both years was achieved in I20 and I80 water deficit conditions, respectively. The concentration of Mg in the I50 and I80 water deficits decreased by 17 and 33% in the first year, and by 14 and 25% in the second year in comparison with well-watered conditions, respectively. Furthermore, the Mg concentration in the first and second year enhanced by 21.7 and 14.1% after application of AMF compared with control, respectively (Table 5).
3.3.6. Fe concentration
The highest Fe concentration of thyme leaves (377.8 and 503.8 mg/kg in 2018 and 2019, respectively) was recorded in the intercropping ratio of 50:50. The Fe content in the intercropping ratio of 50:50 and 66:34 increased by 22 and 6% in the first year and by 25 and 12% in the second year, respectively, when compared with the sole culture. The maximum and minimum concentrations of Fe in both years were achieved in the I20 and I80 water deficit conditions, respectively. The concentration of Fe in I50 and I80 decreased by 22 and 29% (in 2018), and by 18 and 28% (in 2019), respectively, in comparison with I20 treatment. Overall, the Fe concentration in the first and second growing year increased by 18.1 and 14.6%, respectively, after application of AMF compared with control (Table 5).
3.3.7. Zn concentration
In first and second year, the highest Zn concentration was achieved in the thyme sole culture and 50:50 intercropping ratio with non-stressed water deficit (I20), respectively. However, the lowest content of Zn in both years was recorded in thyme sole culture with severe water deficit (I80) (Fig. 4). The Zn content in I50 and I80 water deficit conditions decreased by 11 and 24% (first year), and by 14 and 25% (second year) in comparison with I20 treatment. Also, the Zn concentration increased by 6.3 (first year) and 8.1% with AMF inoculation (Table 5).
3.4. EO content
Between three levels of water deficit, the maximum EO productivity was measured in I50 water scarcity that was 52 and 34% (in 2018), 22 and 4% (in 2019) higher than those observed in I20 and I80 treatments, respectively (Table 4). Based on the interaction of cropping patterns × AMF application, the highest EO content in both years was achieved in the intercropping ratio of 50:50 after AMF application. Also, the lowest EO content in both years was observed in the sole culture of thyme without usage of AMF (Fig. 5).
3.5. EO yield
In the first and second year, application of AMF increased the EO yield by 59.6 and 23%, respectively, in comparison with control (non-AMF). Based on the interaction of cropping patterns × water deficit, the highest EO yield in both years (5.04 and 9.46 g m-2 in the first and second year) was achieved in the non-stress plants (I20) in sole culture (Fig. 6). In addition, the EO yield in the intercropping ratio of 50:50 and 66:44 decreased by 17 and 53% in the first year, and by 19 and 55% in the second year, respectively, when compared with the sole culture. Finally, the EO yield in I50 and I80 water deficit stresses decreased by 3 and 35% in the first year, and by 9 and 31% in the second year, respectively, when compared with well-watered plants (I20) (Table 4).
3.6. EO composition
In total, 29 compounds were identified in the thyme EOs, accounting for 97.87-99.74% and 97.06%-99.57% of the total compositions at the first and second year, respectively (Table 6 and 7).
In the first year, the main EO constituents were thymol (31.12-37.26%), γ-terpinene (13.14-17.48%), p-cymene (11.37-13.92%), camphene (6.52-8.52%), 1,8-cineole (2.94-5.83%), camphor (3.74-5.61%), (E)-caryophyllene (2.57-4.19%), carvacrol (2.01-3.41%) and β-myrcene (1.72-2.31%). The highest content of thymol was achieved in of 50:50 intercrop with moderate water deficit (I50) and application of AMF. The content of thymol in the intercropping ratio of 50:50 and 66:34 increased by 6.3 and 5.9%, respectively, when compared with thyme sole culture. Also, the thymol percentage in the I50 and I80 water deficit increased by 7.7 and 3.5%, respectively, when compared with control (I20). Furthermore, application of AMF increased the content of thymol by 6.3% in comparison with control. The highest content of γ-terpinene was observed in 50:50 intercrop under severe water deficit (I80) and application of AMF. The content of γ-terpinene in the intercropping ratio of 50:50 and 66:34 increased by 14.6 and 4.4% when compared with thyme sole culture. Also, the γ-terpinene percentage in I50 and I80 water scarcity increased by 13.9 and 9.9% when compared with I20. The highest percentage of p-cymene was measured in 66:34 intercropping with severe water deficit (I80) and application of AMF. Also, the p-cymene percentage in I80 water deficit increased by 4.8% when compared with non-stressed water deficit (I20). Furthermore, application of AMF increased the content of p-cymene by 2.7% in comparison with control (Table 6).
In the second year, the main constituents of thyme EO were thymol (40.89-48.59%), γ-terpinene (16.93-21.55%), p-cymene (13.73-16.26%) and carvacrol (2.95-4.06%). Based on the results, the highest percentage of thymol was achieved in the intercropping ratio of 50:50 with moderate water deficit (I50) and application of AMF. The content of thymol in the intercropping ratio of 50:50 and 66:34 enhanced by 4.2% compared with thyme sole culture. Also, the thymol percentage in I50 and I80 water stress conditions increased by 8 and 2.9%, respectively, in comparison with I20. Overall, the application of AMF increased the content of thymol by 2.8% in comparison with control. The highest percentage of γ-terpinene was observed in 50:50 intercropping with severe water deficit (I80) and application of AMF. The content of γ-terpinene in the intercropping ratio of 50:50 and 66:34 enhanced by 6.5 and 7.6%, respectively, when compared with thyme sole culture. Also, the γ-terpinene percentage in I50 and I80 water deficit conditions increased by 7.3 and 9.7%, respectively, when compared with I20. Finally, the application of AMF increased the content of γ-terpinene by 9.3% when compared with control. The highest percentage of p-cymene was measured in 66:34 intercrop under severe water deficit (I80) and application of AMF. The content of p-cymene in the intercropping ratio of 50:50 and 66:34 enhanced by 4.2 and 6.6%, respectively, when compared with thyme sole culture. Also, the p-cymene percentage in I80 water scarcity conditions increased by 5.3%, respectively, in comparison with I20 (Table 7).