Effect of nitrogen application rate on the content and composition of oil, essential oil and minerals in black cumin (Nigella sativa L.) seeds

A field experiment was conducted to study the effect of nitrogen fertility level on the content and composition of oil, essential oil and minerals in black cumin (Nigella sativa L.) seeds. Sixty-three-day-old plants were supplied with varying levels of N, i.e., 0, 30, 60, and 90kg Nha(-1) soil. The fixed oil content of the seeds ranged from 32.7% to 37.8% and it remained almost unchanged at the two higher external N regimes, i.e., 60 and 90 kg N ha(-1), but at 30 kg N ha(-1) the oil content increased significantly. Of the saturated fatty acids analyzed, palmitic acid increased slightly at all external N levels, but in contrast stearic acid decreased considerably at 60 kg N ha(-1). Of the unsaturated fatty acids of fixed oil, the predominant fatty acid was linoleic acid (18:2) followed by oleic acid (18:1). Linoleic acid and dihomolinoleic acid (20:2) showed no change in their amounts at varying levels of N. In contrast, a marked reduction in alpha-linolenic acid (18:3) was found at the two higher N regimes, i.e., 60 and 90 kg N ha(-1). Seed essential oil content did not vary with the change in applied N level. The major component of essential oil of black cumin seed was found to be p-cymene, which showed an increase at 30 kg N ha(-1), whereas no change in the levels of a-pinene or P-pinene was observed at varying levels of N. K, P, Na, Fe, Mn, and Ni were found to be predominant elements in the seeds. Ca, Mg, Cu, and Cr were present in low amounts, but Zn was present in moderate quantity. Increasing N rate did not affect the content of K, P, Ca, Mg, or Cr in the cumin seeds. In contrast, a consistent decrease in seed Mn, Zn, and Ni was observed with increase in external N level. Increasing N level had a marked effect on some of the components of black seed oil. (c) 2006 Society of Chemical Industry.