The effect of nitrogen fertilizers (Urea, sulfur coated urea) with manure on the saffron yield

This research in saffron plant nutrition was done in three areas belonging to Khorasan province (Iran), one in Gonabad region, and other two (Boroon and Eslamieh) in Ferdows region. The experiment was carried out as a Randomized Complete Block Design (RCBD) in five farms of each region, with the sum of fifteen different farms. There were nine treatments with three replications in each farm. They consisted in one control using only (30 Ton/ha) manure as fertilizer, together with other treatments using different rates of (23, 34, 46, 57) Kg/ha pure Nitrogen (N) from two different sources of Urea and Sulfur Coated Urea (S.C.U.), plus the 30 Ton/ha manure as the fertilizer needed for each experiment. Relative Yield was calculated as: Relative Yield (%) = (Treatment Yield in each Expt.*100 / MAX. Yield in the same Expt.) Analysis System package (SAS), in the Eslamieh area of Ferdows region and in Gonabad region, the effect of N fertilizer type on the relative yield of saffron was non-significant. For the N-fertilizer rate there was a significant difference at (a = 0.01 %). However, in the Boroon area of Ferdows region, none of the factors had a significant effect on the saffron yield. Maximum yield obtained in each of the areas of Eslamieh, Gonabad and Boroon were in the order of (7.1, 6.5, 7.01) Kg/ha respectively. Based on the Duncan's Multiple Range Test (DMRT) mean comparison analysis at (a = 0.05 %), for simple and interaction effects of the type and rate of N fertilizer for the Eslamieh area, there was no significant effect for the type, but there was a significant difference on the different rates, such that the maximum yield was obtained from the 3(rd) N rate. It seems that the saffron response to the N-fertilizer is based on the characteristics of the different areas. Meanwhile, if %O.C. and NO3-N of soils are low, 46 Kg/ha of pure N from both (Urea, and S.C.U.) sources plus the (30 Ton/ha) manure can be used, and an increase in saffron yield is expected. Nitrogen amounts higher than (57 Ton/ha), if not reducing the yield, will not increase it significantly. Investigating the effect of higher rates of N above (57 Kg/ha), and also the application time and type of N fertilizer, could be good topics for future research.