Biological and chemical nitrogen fertilizer impact on cumin (Cuminum cyminum L) under different irrigation regimens

Water and nitrogen deficits are the most important limiting factors for plant growth and crop production in the world. Drought stress would be amplified by the global warming. Moreover, nitrogen scarcity is occurred in most arid and semi-arid areas. Cumin (Cuminum cyminum L.) is an important plant due to export benefits and low water demand. This study was aimed to evaluate nitrogen fertilizer effect on yield and some physiological characteristics of cumin under different irrigation regimens.

The experiment was performed based on a split plot as randomized complete block design. Experiment treatments were irrigation regimens (field capacity, irrigation by draining 40% of soil water as middle stress, and irrigation by draining 80% of soil water as severe stress) and nitrogen fertilizers (60 kg ha-1 urea, 30 kg ha-1 urea, Nitroxin, and Nitroxin + 30 kg ha-1 urea).

Drought stress reduced cumin dry weight, seed yield, and chlorophyll content. In contrary, proline content, malondialdehyde (MDA) rate, phenol content, anthocyanin amount, and activity of catalase (CAT) and peroxidase (POX) increased by water stress. Increment urea use resulted in amending cumin growth and seed yield in the field capacity. Also, nitrogen use and raising its rate under the middle water stress caused to improve cumin drought tolerance. However, under the severe water stress, nitrogen application had not a significant impress on drought acclimation and seed yield.

Nitroxin inoculation with use of 30 kg ha-1 urea was the most effective treatment to ameliorate seed yield and drought tolerance.