Different N fractions and their relationship with available nitrogen, yield and nutrient uptake in safflower (Carthamus tinctorious) in Vertisol

A field experiment was carried out during rabi season of 2007–08 on Vertisol at Marathwada Agricultural University, Parbhani, India to assess the relation of N fraction with available pool and supply of N in safflower. Total nitrogen, NO₃-N, NH4-N, total hydrolysable-N, organic ammonia content and acid insoluble N significantly increased with integrated nutrient management. The highest values of these parameters were recorded with treatment full recommended dose of fertilizer (RDF) + vermi-compost @ 5 mg ha⁻¹ + vermi-wash spray + Azotobacter + phosphate soluble bacteria (PSB)+cow dung urine slurry (CDUS) at criticalgrowth stage) followed by 50% RDF + vermi-wash spray+Azotobacter + PSB + CDUS at critical growth stage and vermi-compost @ 2.5 mg ha-¹ + vermi-wash + Azotobacter+PSB + CDUS at critical growth stage. Available N showed significantly positive correlation with total N, nitrate N, ammonical N, total hydrolysable, organic ammonia and acid insoluble N after harvesting (r = 0.803**, 0.977**, 0.974**, 0.970**, 0.883** and 0.970**, respectively). Yield showed significantly positively correlated with total N, NO₃-N, NH₄-N, total hydrolysable N, organic ammonical N and acid insoluble N related with yield correlation coefficient (r = 0.941**, 0.931**, 0.974**, 0.966**, 0.745** and 0.668*, respectively) and it also showed positive correlation with uptake of nutrients. The multiple regression equation showed that 99% relative contribution of various N fractions to safflower yield and uptake of nutrients.