Optimization of Manure and Irrigation Levels on Flower and Corm Yields of Saffron by Using a Central Composite Design

The purpose of this experiment, evaluation of cow manure and irrigation levels on flower and corms of saffron using Central Composite Design was done with 13 treatments and two replications at the Research Field of the Ferdowsi University of Mashhad during two growing seasons of 2017-2018 and 2018-2019. The treatments were based on low and high cow manure levels (0 and 80 t.ha-1, respectively) and water (120 and 50 percent of water requirement, respectively). The results showed that the linear component's effect was significant on (p≤0.05) daughter corm diameter and numbers of daughter corms for 4-8 g. The square component's effect was significant on (p≤0.05) flower number, fresh weight of flower, the dried weight of stigma, and daughter corm diameter. The interaction effect of full quadratic was significant (p≤0.05) on the dried weight of daughter corms. Lack of fit test had no significant effect on the studied traits. The response variables' full square model gave insignificant lack-of-fit, indicating that the data were satisfactorily explained. The highest values of dried weight of stigma, fresh weight of flower, and flower number were observed for 16 t cow manure per ha+ 5440 m3 water per ha (with, respectively 0.65 and 27.75 g.m-2and 60 No.m-2). The maximum amount for dried weight of daughter corms was observed for 32 t cow manure per ha+ 3200 m3 water per ha (with 4463.31 g.m-2). It is necessary to use 4693.33 m3 water per ha 30.12 t cow manure per ha to obtain optimum conditions under the economic scenario (with desirability index= 0.72).