Effect of Bio and Chemical Fertilizers on Some Physiological Responses and Yield of Black Cumin under Different Irrigation Levels

In order to investigate the effects of integrated management of chemical and biological fertilizers on physiological traits, and grain yield of black cumin (Nigella sativa L.) under different irrigation levels, a split-plot experiment has been conducted based on a randomized complete block design with four replications at research farm University of Kurdistan in the spring of 2016. Two irrigation levels (irrigation at 100% and 70% of the plant water requirement) are randomized on the main plot. Five fertilizer levels (including 100% chemical fertilizers, 80% chemical fertilizers + biofertilizers, 60% chemical fertilizers + biofertilizers, 40% chemical fertilizers + biofertilizers, and non-fertilizer application) are randomized on a sub-plot. The results reveal that under irrigation at 70% of the plant water requirement conditions, proline concentration, soluble carbohydrates concentration, and lipid peroxidation have increased, while the values of other studied physiological parameters as well the grain yield have dropped. The combination of biological and chemical fertilizers positively affect the studied physiological traits and grain yield, such that the highest grain yield belongs to the combined treatment of 60% chemical fertilizers + biofertilizers (798.18 kg ha-1), showing an increase of 37.22% compared to the control (without fertilizer). Due to the positive effects of combining bio-chemical fertilizers on physiological parameters and grain yield, it is recommended to replace the combination of bio-chemical fertilizers instead of employing only chemical fertilizers.