Effect of Irrigation and Planting Date on Yield and Water Use Efficiency of Ajowan (Carum copticum)

Aims: This study was conducted to evaluate the effect of irrigation regimes and different planting dates on yield and water use efficiency of ajowan.
Place and Duration of Study: The study was carried out during 2009/2010 and 2010/2011 seasons in Birjand, Iran.
Methodology: Experimental design was split plot based on randomized complete block with three replications. Irrigation intervals (irrigation cut at the beginning of flowering and complete irrigation) as the main factor and six planting dates (December 6, December 21, January 5, February 29, March 30 and April 30) as sub factors.
Results: Results showed that the highest and lowest seed yields and number of seeds per plant was from planting dates of February 29 and March 30, respectively. Results showed that late planting decreased seed yield, number of umbels per plant and number of seeds per plant; but increased number of seeds per umbel and 1000-seed weight. Winter planting had higher yield and biomass water use efficiency compared to spring planting but seed water use efficiency and harvest index were not affected by planting date. The effect of the water stress treatment on plants’ reproductive structures caused decreases to seed yield, seed water use efficiency and seed harvest index.
Conclusion: In general, these showed that winter planting in conditions of drought stress resulted in higher biomass water use efficiency.