In order to study competition response among saffron corms, a split plot experiment was conducted based on a complete randomized block design with three replications in a field in Ashkezar City of Yazd province for 3 years. The main plots were irrigation with three levels (100%, 75%, and 50% of ETc) and the subplots were fertilization management methods including control (without any fertilizer or manure), applying 10 t.ha-1 cow manure, 10 t.ha-1 vermicompost both by spreading, 10 t.ha-1 or 5 t.ha-1vermicompost buried under planting corm rows, 10 l.ha-1 Humaster Saffron fertilizer for 1 or 2 times after flowering during irrigation. Results showed that under moderate water stress in comparison with control, total corm number and total corm weight per plant declined by more than 30% and 17% respectively. But the average corm weight was enhanced by 12%. Total effective corm weight and total effective corm number declined by more than 50% under strict water stress in comparison with control. During 3 experimental years, total effective corm number, total effective corm weight, total corm number, and total corm weight were increased by 189%, 205%, 470%, and 263% respectively while average corm weight, effective corm weight ratio, and effective corm number ratio were declined by 38%, 17%, and 48% respectively. In summary, results showed that increases in corm weight per plant during experimental years were mostly a result of increasing in corm numbers. Although, big corms per small corms decreased year by year as a result of competition among corms. Under moderate stress water, the saffron plant grew up each corm weight in comparison with increasing corm number per plant while under strict water stress allocated assimilates among more corms and increases corm numbers per plant.

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