Ph.D. Dissertation:

Agrophysiological response of cumin to Irrigation interruption time and type of cultivation in weed interference and non-interference conditions

In order to investigate the agrophysiological response of cumin to irrigation cut-off time and type of cultivation in interference and non-interference of weeds conditions, the experiments were performed as a split split plot in a randomized complete block design with three replications in Hakmabad Joven Agricultural Service Center (Khorasan Razavi) in the two cropping years 2018 and 2019. Irrigation cut-off time (full irrigation, irrigation cut-off in flowering stage, irrigation cut-off in seed-filling stage and rainfed cultivation) were considered as main plot, Planting method conventional and organic) as a sub plot and weed interference (interference and non-interference) was considered as sub-sub plot. The results showed that in the rainy year, the yield and yield components of cumin did not respond to irrigation cut-off times, but in the drought year, the highest seed and essential oil yield was obtained with full irrigation and delay in cessation of irrigation had less negative effects on yield and yield components. In both years, rainfeed cultivation produced the lowest seed yield and essential oil and the highest percentage of essential oil in both conventional and organic growing conditions, and supplementary irrigation in both conditions increased grain yield and essential oil and decreased the percentage of essential oil. In both cropping conditions, no statistically significant difference was observed between complete irrigation and cessation of irrigation at the grain stage. And in rainy year when the amount of rainfall was more than water needs, full irrigation reduced grain yield and essential oil by reducing yield components such as the number of umbrellas per plant and the number of seeds per umbrella. While cuminal (20.7%) was the main component of the essential oil in cut-off irrigation in the seed formation stage, ?-terpinene (20.8-25.84%) was the main component of essential oil in other irrigation regimes. The percentage of compounds detected in organic cultivation was higher than in conventional cultivation. In organic cultivation, ?-terpinene (25.6%), cuminal (20.6%), ?-pinene (13.8%), and p-Cymene (10.1%) and under conventional conditions, ?-Terpinen-7-al (21.4%), p-Cymene (21.1%), cuminal (16.3%) and ?-Pinene (11.1%) were the main components of the essential oil. Weed interference significantly reduced height, number of lateral branches, number of umbels per plant, number of seeds per umbel, 1000-seed weight, seed yield and essential oil yield, but essential oil percentage was not affected by weed interference. Weed interference in all irrigation regimes reduced yield and yield components. Delays in cessation of irrigation produced more grain and essential oil yield in both interference and non-interference conditions. In general, the results of this experiment showed that irrigation cut-off at the time of sowing is able to produce good seed yield in both conventional and organic condition without weed interference. Although the yield was higher in conventional cultivation, the quality of essential oil produced under organic cultivation was better than conventional cultivation. Accordingly, due to the importance of essential oil compounds, organic cultivation of cumin along with weeding during the growing season and cessation of irrigation in the seed closure stage is recommended for the proper quantitative and qualitative production of cumin. Although the seed yield is higher in conventional cultivation, the quality of essential oil produced under organic cultivation was better than conventional cultivation conditions. Consequently, due to the importance of essential oil compounds, organic cultivation of cumin and full irrigation is recommended for adequate quantitative and qualitative cumin production

Keywords: Competition, Drought Stress, Irrigation Regime, Weed Interference Cultivation system, cumin, oil qua