Determination of the effects of different sources of salt and salinity levels on growth, efficiency and quality parameters of black cumin

Excess salinity, osmotic stress, harmful effects of toxic ions and ion imbalance negatively affect plant growth and development. Many crops, including black cumin (Nigella Sativa L), are classified as salt-sensitive plant species as they are significantly affected by salt stress, one of the abiotic stress factors. However, no study has been found in the world literature that reveals the effects of different salt sources (TK) and irrigation water salinity levels (TD) on black cumin. The main purpose of this study was to determine the effects of salinity levels created separately by different salt sources on the soil and drainage water salinity and the plant water consumption, growth, yield and quality parameters of the black cumin. The research was carried out for one growing season between November-2020 and May-2021 under semi-controlled conditions in a rain-out shelter area at Akdeniz University. In the study, six different salt sources (CaCl2, MgCl2, NaCl, Ca(NO3)2, MgSO4 and Na2SO4) and four different irrigation water salinity levels for each salt type (TD0 = 0.6 dS/m, TD1 =1.5 dS/m, TD2 = 2.5 dS/m and TD3 = 5.0 dS/m) were investigated. The result showed that, the number of branches did not show statistically significant difference between treatment under the main factor TD, whereas the obtained changes were between 1.00 (TD0) and 6.18 (TD3) dS/m for soil salinity, 0.79 (TD0) and 5.21 (TD3) dS/m for drainage water salinity, 346.5 (TD3) and 373.6 (TD0) for plant water consumption mm/season, 119.5 (TD3) and 135.7 (TD2) cm for plant height, 2.22 (TD2) and 2.45 (TD0) g/plant for vegetative dry weight, 1.36 (TD1 ) and 1.69 (TD0) for number of capsules per plant, 97.6 (TD2) and 116.0 (TD0) mg/plant for seed weight, and 16.8% (TD3) and 27.8 (TD2) for seed oil content. Similarly, soil salinity, plant water consumption, plant height, number of branches, vegetative dry weight and seed oil content did not show statistically significant difference between the treatments under the main factor TK, whereas the were ranged between 2.27 (Na2SO4) and 2.73 (MgCl2) dS/m for drainage water salinity, 1.40 (Na2SO4) to 1.65 (MgCl2) for number of capsules per plant and 89.0 (Na2SO4) and 117.9 (MgCl2) mg/plant for seed weight. With significant interaction between the main factors, the highest number of seeds per plant was observed under MgCl2-TD1 (49.1) and MgSO4-TD1 (42.0) treatments and the highest average seed moisture content (between 15.9% and 16.9%) was obtained with all TKs under TD3 treatment. It was revealed that the slope values of CaCl2, MgCl2, Ca(NO3)2, MgSO4 and Na2SO4 salt sources were as low as 0.60, 1.47, 3.91, 2.95 and 1.29%, respectively, while the threshold salinity values of these salts sources for the seed weight of the black cumin could not be determined. For the NaCl salt source, the threshold salinity and slope values were determined as 2.56 dS/m and 1.73 % / dS/m, respectively. Threshold salinity values for black cumin seed oil content were relatively high under salt sources containing Mg and relatively lower under salt sources containing Ca. In addition, it was determined that the slope values were relatively lower under the Ca-containing salt sources and relatively lower under the Na-containing salt sources. As a result, it can be suggested to consider both the salinity of the irrigation water and the salts in the irrigation water for black cumin growth, since the salinity threshold and slope values for the seed yield and seed oil content of the plant vary depending on the salt types in the irrigation water.