Interactive Effects of Phosphorus Nutrition and Atmospheric Carbon Dioxide Levels on Growth, Nitrogen Fixation and Yield of Green Gram

摘要

Experiments were conducted to study the effect of phosphorus (P) nutrition on growth and physiological mechanisms associated with biomass accumulation and yield in green gram [Vigna radiata (L.) Wilczek] cutivars ML-818 and PDM-139 under ambient (390±50 μmol mol~(-1)) and elevated (550±50 μmol mol~(-1)) levels of carbon dioxide (CO2). Seeds sown in pots with sufficient-P (supplied with 17.9 mg P2O5 kg~(-1) soil) and low-P (receiving no external P supply) were exposed to the elevated and ambient CO2 levels in the open top chambers (OTC). Biomass accumulation increased under elevated CO2 level in both the varieties, with maximum increase occurring at the arithesis stage. Plants responded to elevated CO2 level even under low-P supplies and accumulated biomass comparable to that obtained in the plants grown with sufficient-P under ambient CO2 level. Number of nodules and nodule fresh weight increased under sufficient-P and elevated CO2 treatment; 3-folds increase observed in nitrogenase activity maximized the tissue nitrogen concentration and uptake. Number of pods per plant, 100-seed weight and seed yield increased with P addition. Number of seeds per pod remained unaffected at the elevated CO2 level. Although yield was higher in both the varieties under elevated CO2 levels, better yield stability was obtained in PDM-139 as was evident from lesser yield reduction under low-P level as compared to the sufficient-P at the elevated CO2 level. It leads to a conclusion that fertilising green gram with phosphorus at the elevated CO2 level improves the nutrient acquisition, thereby facilitating maximum growth and grain yield.