The effect of cobalt application on the growth, nodulation and nitrogen fixing capacity of sesbania rostrata

The effect of cobalt at 0.5, 1.0, 1.5 ppm as investigated on the dry matter yield, nodulation response (number and weight of nodules plant-1) and nitrogen fixing capacity of sesbannia Rostrata in a pot culture experiment. The results revealed that application of cobalt did not improve nodulation, however, it significantly improved the nitrogenase activity of nodules. Increasing rates of cobalt increased the dry matter yield of shots and roots by 48.2, 49.4, 58.5 percent as compared to control. All the applied doses of cobalt significantly improved the N concentration and uptake by Sesbania Rostrate. The increase in shoots N uptake was up to 134.5 percent and in roots up to 62.2 percent. It is thus clear that application of cobalt greatly improved the nitrogenase activity and n-fixing capacity of sesbania rostrta which in turn increased the dry matter yield of plant. The rate of 0.5 ppm cobalt was the optimum dose in the experiment. (author)