Effects of Different Water Supply and Corm Planting Density on Crocin, Picrocrocin and Safranal, Nitrogen Uptake and Water Use Efficiency of Saffron Grown in Semi-Arid Region

Abstract

Saffron’s color, taste and odor result from the chemicals crocin, picrocrocin and safranal, respectively. Hence, in addition to quantitative yield, secondary metabolites content are known as crucial factors for a successful saffron production. Moreover, enhancing resources efficiency, especially water and nitrogen, is becoming increasingly important for agricultural improvement in arid and semi-arid regions. Thus, the effects of irrigation levels and corm planting on crocin, picrocrocin and safranal content, water use efficiency (WUE) as well as nitrogen use efficiency (NUE) of saffron were investigated as a two-year field experiment based on a randomized complete block design arranged in split-plot with three replicates. The irrigation levels (100, 75 and 50% of saffron water requirement) and corm planting pattern (50, 100, 200 and 300 corms m^-2) were allocated to main and sub-plots, respectively. Based on the results, crocin and picrocrocin content increased with decreasing irrigation levels. The highest WUE_S (WUE based on dry stigma yield) was obtained when 50% of saffron water requirement was supplied. However, the lowest WUE_C (WUE based on daughter corms yield) and NUE_C (NUE based on daughter corms yield) were obtained when 50% of saffron water requirement was applied. Irrespective of irrigation levels, WUE_S, WUE_C and NUE_C increased with increasing the planting density. The results demonstrated that although relatively severe water stress increases WUE_S and secondary metabolites in saffron stigmas, it could decrease WUE_C and NUE_C through affecting daughter corm growth.