Effect of plant density and phosphorus resources on yield and yield components of Black cumin (Nigella sativa L.) medicinal plant in dryland farming

In order to investigate the effect of plant density and phosphorus resources on yield and yield components of black cumin (Nigella sativa L.), medicinal plant, at dryland conditions, a split-plot experiment based on randomized complete block design with three replications was conducted at Soil and Water Conservation Research Center, University of Tehran, located in kouhin dryland farms in Qazvin Province, Iran in 2016-2017. Phosphorus resources were chemical Phosphorus (150 kg/ha di-ammonium phosphate or control) (p1), 50% chemical Phosphorus + 50% biological Phosphorus (p2), biological Phosphorus Barvar II® alone (p3) and plant density levels were (d1)20, (d2) 30 and (d3)40 plants/m2. Results showed that interaction effect between plant density and phosphorus resource were significant on number of capsule per plant, number of grain per capsule, number of grain per plant, grain yield, biological yield and harvest index. Also number of grain per carpels was affected by phosphorus treatment, but the number of carpels per capsule and 1000 grain weight were not significant. The highest grain yield (206.25 kg/ha) was obtained from biological Phosphorus fertilizer application (P3) with 40 plants/m2 plant density and the lowest grain yield (42.34 kg/ha) was recorded for control (P1) treatment with 40 plants/m2 plant density. So, application of biological phosphorus and high plant density (40 plant/m2) had the highest grain yield however, chemical phosphorus (control) in high plant density produced the lowest grain yield.