tIn order to investigate the effects of sulfur (S) oxidation and vermicompost (V) application on black seed(Nigella sativa L.) oil yield and its nitrogen and phosphorus uptake, a two-year field experiment wasconducted at Faculty of Agriculture, Ferdowsi University of Mashhad, Iran in a calcareous soil during2013 and 2014. A randomized complete block design arranged in factorial with four replications wasused to analyze 12 treatments. The calcareous soil amendments (control, V + Thiobacillus thiooxidans(T), S + T and V + S + T) and three levels of P (0, 30 and 60 kg ha−1) were considered as the first and thesecond experimental factors, respectively. All calcareous soil amendments (V+ T, S+ T and V + S + T) causeda significant reduction in soil pH, and a significant increase in electrical conductivity (EC). In addition,calcareous soil amendments showed a considerable effect on soil available P content. The highest grain,oil and essential oil yields were obtained from V + S + T treatment. The soil amendments significantlyincreased N and P concentration in plants and improved P harvest index. Although a positive correlationwas observed between P and N concentration, there was a negative correlation between grain yield and Puse efficiency. It seems that any approach that would allocate more P to seeds, during seed developmenton the mother plants, would increase final yield in black seed.

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