Effect of different doses of nitrogen on nitrogen fixation and yield of lentil using tracer technique

Legumes play a predominant role in nitrogen cycling having the unique features of biological nitrogen fixation. An experiment was conducted to estimate yield, nitrogen use efficiency (NUE) and the proportion of nitrogen fixation in plant segments i.e. roots, shoots, leafs and seeds of lentil. Three treatments such as 0 kg/ha, 11.5 kg/ha and 25.3 kg/ha were used in this experiment. The highest dry matter yield obtained were 43.44 kg/ha, 2677 kg/ha, 1450 kg/ha and 1604 kg/ha at roots, shoots, leaves and seeds respectively with the treatment 11.5 kg/ha N level. ¹⁵N labelled urea was applied to wheat and lentil at 5% ¹⁵N atom excess. The total nitrogen content in lentil was found 8.39 % with an average yield of 104.5 kg N/ha whereas it was 1.95% with an average yield of 102.8 kg N/ha in case of wheat. Nitrogen derived from fertilizer in lentil was 1.173% with an average fertilizer N yield of 12.085 kg/ha whereas it was 7.538% with an average yields of 223.16 kg N/ha in wheat. Lentil fixed around 85% of its required nitrogen from atmosphere through biological fixation and a minimal amount of 14.387% of nitrogen was drawn from soil source. Nitrogen use efficiency in seed was 110.1 % in lentil and 36.22% in wheat which were much higher than the other plant segments in both cases.