Influence of hydrogel polymer and NO3-: NH4+ ratios on dill (Anethum graveolens L.) seed essential oil composition and yield

To evaluate the effects of hydrogel polymer levels (0, 10, 20, 30 g m-2) and NO3:NH4 ratios (0: 100, 25: 75, 50: 50, 75: 25, and 100: 0) on dill seed yield and its essential oil constituents, an experiment was conducted in October 2012 in the experimental field of Islamic Azad University, Jiroft, Iran. Results showed that using 30 g m-2 hydrogel polymer with 75NO3-: 25 NH4 ratio produced maximum seed yield and the same plus 100NO3-:0NH4 led to a max essential oil yield. GC-MS analysis indicated that major constituents of dill seed oil were carvone, limonene, dillapiole, α-phellandrene, and trans-dihydrocarvone. The interactive effects of concurrent use of hydrogel polymer and NO3-:NH4 ratios on the constituents were evaluated: non-use of super-absorbent polymer reduced components like α-terpinene, limonene, dillapiol, and trans-carvone, whereas its addition to such compounds as α-phellandrene, p-cymene, carvone, and trans-dihydrocarvone left a negative effect. In most cases, application of nitrate above 50℅ and reducing ammonium positively increased the compounds.