The Effect of Biochar Application and Planting Pattern on the Physiological and Biochemical Traits of Garden Thyme (Thymus vulgaris L.) at Different Levels of Irrigation

Water scarcity is a principal limitation for production in arid and semi-arid regions. Biochar increases the water-holding capacity of the soil in drought-stress conditions. To investigate the effect of biochar and planting patterns on the physiological, biochemical, and thyme (Thymus vulgaris L. (essential oil traits, an experiment was carried out as a factorial split-plot based on a randomized complete block design for two crop years (2017-2019). The findings revealed that furrow irrigation treatments, both fixed and variable, decreased the flowering branches' yield, relative water content, total chlorophyll, Chlorophyll a, and thymol percentage. Instead the essential oil yield, proline content, soluble sugar content, chlorophyll b, and carvacrol under these treatments increased. The decrease in flowering branches yield and the relative water content in variable alternate furrow irrigation was lower compared to fixed alternate furrow irrigation. Biochar application reduced the effects of drought stress caused by variable alternate furrow irrigation and fixed alternate furrow irrigation treatments but had no significant impact on chlorophyll b, thymol percentage, and total chlorophyll. The highest carvacrol and thymol percentages were obtained in fixed alternate furrow irrigation, variable alternate furrow irrigation treatments, and irrigation of all furrows, respectively. The planting pattern did not affect flowering branch yield, relative water content, soluble sugars content, and proline content. The highest essential oil yield (24.73 kg/ha) was obtained in the treatment combination of variable alternate furrow irrigation, biochar application, and Planting double rows of thyme on the ridge. The study recommended that farmers must observe alternate furrow irrigation methods and biochar application (amount 8 t/ha) as a better option in the limited water environment.ABBREVIATIONFI: Full irrigation, FAFI: Fixed Alternate Furrow Irrigation, VAFI: Variable Alternate Furrow Irrigation, POR: planting a single row of thyme on the ridge, PTR: planting double rows of thyme on the ridge, BC: Biochar application, NBC: No application of biochar, FBY: Flowering branch yield, SUGC: Soluble sugars content, RWC: relative leaf water content, Chl a: Chlorophyll a, Chl b: Chlorophyll b, T Chl: Total Chlorophyll, EOY: Essential oil yield, CVR: Carvacrol, and THYM: Thymol.