Abstract
Two-line hybrid rice (2LH) is accompanied by more nitrogen (N) input. To explore the difference in response of two-line and three-line hybrid rice (3LH) to N application, a three-year split-plot experiment was conducted. Three 2LHs and three 3LHs were set as main plots, and four N rates including 0 kg ha−1 (N0), 90 kg ha−1 (N90), 150 kg ha−1 (N150), and 210 kg ha−1 (N210) were set as subplots. 3LH had more panicles and yielded 7.95%, 6.31%, and 5.48% higher than 2LH in N0, N90, and N150, respectively. 2LH had a greater panicle weight in N210 and yielded 1.45% higher than 3LH. Leaf area index (LAI) had the greatest effect on the yields of both 2LH and 3LH, while the contribution of light extinction coefficient (K) was 46.35% and 12.80% those of LAI, respectively. The LAI, K, and radiation interception rate (RIR) of 2LH were smaller than those of 3LH in N0 and N90. The K of 2LH increased significantly as the N rate increased from 150 kg ha−1 to 210 kg ha−1, while that of 3LH showed no significant change, making the maximum RIR of 2LH greater than that of 3LH. 2LH, which intercepted more radiation through greater leaf extension to achieve higher yields, was able to use nitrogen fertilizer efficiently under a high N rate in China.
Highlights
As nitrogen (N) is the main factor affecting rice yield, optimizing N management is important to achieve a continuous rice yield increase in China
Sterile lines have to cross with maintainer lines to produce seeds as their sterility is determined by the cytoplasm and the nucleus, and sterile lines cross with restorer lines to produce hybrid rice seeds for field production
In N210, 2LH had a greater advantage in panicle weight and yielded 1.45% higher than that of 3LH
Summary
As nitrogen (N) is the main factor affecting rice yield, optimizing N management is important to achieve a continuous rice yield increase in China. Many studies have focused on the genotypic differences in N uptake and utilization among rice varieties, including different growth periods, different sink sizes, and different panicle weights [4,5,6] Those studies have provided references for N fertilizer reduction in rice production, the N use efficiency cannot serve directly as the basis for N fertilizer reduction. Due to the scarcity of public reports on the N tolerability difference between 2LH and 3LH, increasingly higher N rates are being applied to 2LH, resulting in a much slower increase in AEN of rice production in Southwest China than those of the other regions, which reduces the economic benefits of rice production, and contradicts the fertilizer reduction policy of China. This study could provide valuable theoretical support and technical guidance for the targeted N management practices of 2LH and 3LH
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