Influence of seedling age and nitrogen application on photosynthesis and yield of rice (Oryza sativa) grown under waterlogged condition

Rice seedlings of three different age groups, i.e.,30, 45 and 60 days old were grown with three different N levels, i.e.,0, 20 and 40 kg ha−1for two consecutive years under waterlogged condition. The highest yield was obtained with 40 kg N ha−1in crop grown with 60 day old seedlings in both the years. Higher dosage of N application as mud ball showed higher stomatal conductance, net photosynthesis and transpiration. The response of N was better in crop grown with older seedlings. Grain yield showed significant positive relationship with net photosynthesis rate (r= 0.82**) and carboxylation efficiency (r= 0.81**) than with stomatal conductance (r= 0.66), and could be critical determinant for better yield in crop grown with older seedlings at higher N level under waterlogged condition.