Date Received: 07-02-2025 / Date Published: 21-02-2025
The rice lines that have high number of grains per panicle often have low filled-grain rate, probably attributable to an imbalance between source and sink in plants. Thus, studies on technical management such as fertilization to enhance photosynthetic rate and to improve proper sources for high sinks. Soil pot experiments were conducted in 2023 spring and autumn cropping seasons to assess the effects of three N levels, viz. 0, 1, and 2g N pot-1 on photosynthesis at heading and ripening stages of DCG31 (carrying GN1a gene) and Khang dan 18. The obtained results showed that high applied N fertilizer enhanced photosynthetic rate and its related parameters. It helped maintain high photosynthesis, chlorophyll content, leaf area, and dry matter during the heading-ripening stages. The good maintenance of functional green leaves during the seed-setting period led to an increase in grain yield, especially in the spring season. Compared to the normal N dose, the high N application improved 26.4% of the grain yield in DCG31 (57.3g plant-1), whereas that was 6.7% in the KD18 (43g plant-1). Increasing applied N also led to an improved number of panicles per plant and number of filled grains per panicle and did not reduce nitrogen use efficiency, especially in the spring season.
