Response of black cumin (Nigella sativa L.) to digested fertilizer and humic acid in the sustainable agricultural system

The present study was conducted to investigate the effects of natural and organic fertilizers, compared to chemical fertilizers on quantitative and qualitative characteristics of black cumin.

Factorial experiment was carried out in a randomized complete block design with two factors and three replications at the Research Farm of the University of Kurdistan during 2021 growing season. The first factor consisted of three levels of fertilizer (control, digested fertilizer, and chemical fertilizer) and the second factor included three concentrations of humic acid foliar application (0, 200, and 400 mg.L-1).

The digested fertilizer significantly increased plant height, capsules number per plant, seeds number per capsule, grain and biological yield, oil percentage and yield, and essential oil yield. These mentioned traits significantly increased with humic acid foliar application except for essential oil yield. The third level of humic acid had the most effect. The highest values of seed nitrogen and phosphorus content belonged to the integrated treatment of digested fertilizer and 400 mg.L-1 humic acid.

The digested fertilizer and humic acid (400 mg.L-1) improved the quantitative and qualitative characteristics of black cumin and they can be alternative inputs for chemical fertilizers.