Industrial Crops and Products 77 (2015) 167–174 Contents lists available at ScienceDirect Industrial Crops and Products jo ur nal home p age: www.elsevier.com/locate/indcrop Influence of phosphorus and soil amendments on black seed (Nigella sativa L.) oil yield and nutrient uptake Seyyed Mohammad Seyyedi a , Parviz Rezvani Moghaddam a , Mohammad Khajeh-Hosseini a,∗ , Hamid Shahandeh b a Department of Agronomy, Faculty of Agriculture, Ferdowsi University of Mashhad, Iran b Department of Soil & Crop Sciences, Texas A&M University, USA a r t i c l e i n f o Article history: Received 26 June 2015 Received in revised form 27 August 2015 Accepted 30 August 2015 Keywords: Essential oil yield Oil yield Phosphorus acquisition efficiency Phosphorus harvest index Thiobacillus thiooxidans a b s t r a c t In 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 was conducted at Faculty of Agriculture, Ferdowsi University of Mashhad, Iran in a calcareous soil during 2013 and 2014. A randomized complete block design arranged in factorial with four replications was used 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 the second experimental factors, respectively. All calcareous soil amendments (V+ T, S+ T and V + S + T) caused a 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 significantly increased N and P concentration in plants and improved P harvest index. Although a positive correlation was observed between P and N concentration, there was a negative correlation between grain yield and P use efficiency. It seems that any approach that would allocate more P to seeds, during seed development on the mother plants, would increase final yield in black seed. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Black seed (Nigella sativa L.), an annual flowering plant from the Ranunculaceae family, is often cultivated in semi-arid areas (D’Antuono et al., 2002), especially, in Iran (Ghamarnia et al., 2010). The black seed distribution is extended from southern and eastern- rim of the Mediterranean basin countries such as Egypt and Turkey to India (Atta, 2003; Gharby et al., 2015; Tuncturk et al., 2011). The black seed has been used as a medicinal plant because of its spe- cific anti-microbial, anti-tumor and anti-inflammatory properties (Ali and Blunden, 2003; Salem, 2005). In addition, powerful antiox- idant compounds in the seeds have been documented (Erkan et al., 2008). Black seed oil is considered as a new source of edible oil (Piras et al., 2013). Abbreviation: PAE, phosphorus acquisition efficiency; PUTE, phosphorus utiliza- tion efficiency; PUE, phosphorus use efficiency; PHI, phosphorus harvest index. ∗ Corresponding author at: Department of Agronomy, Faculty of Agricul- ture, Ferdowsi University of Mashhad, P.O. Box 91779 48974, Mashhad, Iran. Fax: +98 5138796841. E-mail address: saleh@ferdowsi.um.ac.ir (H. Shahandeh). Phosphorus (P) is one of the most influential factors to improve the performance and quality of black seed (Mohamed et al., 2000; Rana et al., 2012; Shirmohammadi et al., 2014). According to the results of Tuncturk et al. (2011), in P deficient soils, the recommended dose of P for obtaining maximum grain yield is 30–40 kg ha −1 . However, soils with high amount of calcium car- bonate often exhibit low P availability, which is one of the most important problems in crop nutrition, especially, in arid and semi- arid regions of Iran (Sameni and Kasraian, 2004a,b). Hence, the P uptake by black seed might be affected by excessive amounts of calcium carbonate in soil. Calcareous soil is defined as “having the presence of significant quantities of free excess lime (calcium or magnesium carbon- ate) with pH greater than neutral, typically 7.5–8.5” (Hopkins and Ellsworth, 2005). In some cases, the low P uptake in calcareous soils does not mean a low level of P in the soil, in other words, due to for- mation of poorly soluble P complexes with calcium, available P can become unavailable as calcium phosphate (Hopkins and Ellsworth, 2005; Ozturk et al., 2005). In highly calcareous soils of Iran, cal- cium carbonate equivalent reaches up to 650 g kg −1 (Adhami et al., http://dx.doi.org/10.1016/j.indcrop.2015.08.065 0926-6690/© 2015 Elsevier B.V. All rights reserved.