relation between the increasing soluble phosphorus and nitrogen uptake and its effects on phosphorus harvest index of black seed

in order to evaluate the effect of increasing soil soluble phosphorus (p) and its effect on nitrogen (n) and p uptake, p uptake efficiency and p harvest index of black seed (nigella sativa l.) in a calcareous soil; a field experiment was conducted as factorial layout based on a randomized complete block design with three replications at research station, faculty of agriculture, ferdowsi university of mashhad, iran, in year 2013. the experimental treatments were all combination of soil amendment in four levels (vermicimpost (v) + tiobacilus (t), sulfur (s) + t, v+s+t and control) and three levels of phosphorus (0, 30 and 60 kg.ha-1). results showed that s+t and v+s+t had significant effects on reducing soil ph (by 0.94 and 0.61 units, respectively). the resources of soil amendment (v+t, s+t and s+v+t) significantly increased the p uptake by plant and p harvest index of black seed. a significant positive correlation was observed between p and n concentration of plant. however, there was a significant negative correlation between grain yield and p uptake efficiency of black seed.