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This article in AJ

  1. Vol. 103 No. 2, p. 441-448
     
    Received: Sept 27, 2010
    Published: Mar, 2011


    * Corresponding author(s): jinjian29@hotmail.com
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doi:10.2134/agronj2010.0344

Leaf Nitrogen Status as a Main Contributor to Yield Improvement of Soybean Cultivars

  1. Jian Jin *,
  2. Xiaobing Liu,
  3. Guanghua Wang,
  4. Judong Liu,
  5. Liang Mi,
  6. Xueli Chen and
  7. Stephen J. Herbert
  1. Key Laboratory of Black Soil Ecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, PR China

Abstract

The N demand would increase with genetic improvement of soybean [Glycine max (L.) Merr.] yield. Since yield improvement largely attributes to photosynthetic rate, which requires considerable N-derived enzymes to activate the photosynthetic metabolism, the variation of leaf N status over time and its association with nodulation are essential for understanding the mechanism of genetic gain of yield. In agronomic practice, this is also necessary for developing N management in combination with newly released cultivars to increase N use efficiency and yield. However, these issues have not been addressed in Northeast China, where is a major area of soybean production. A field experiment was conducted with 45 representative soybean cultivars, from maturity groups (MG) 00 to 0, released from 1950 to 2006 in Northeast China. The leaf N concentration and content at R5 had positive correlations with the year of release (P < 0.001) with 23.0 and 39.3% of rises over the period, respectively. Nitrogen content per unit area had been improved significantly (P < 0.01), resulting in a 1.08% increase per year. Both photosynthetic rate and C assimilation had significantly positive association with leaf N concentration or N content per unit area, which suggests that both indicators of leaf N status could be essential contributors to genetic yield improvement. The stable content of leaf N across different environments was enhanced over years, which could contribute to yield stability. Among soybean cultivars released across 56 yr, nodule number and fresh weight were progressively increased and a close and significant correlation between leaf N concentration and nodule fresh weight was observed. This indicates that modern cultivars have a better leaf status that poses superior nodulation ability than their predecessors.

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Copyright © 2011. American Society of AgronomyCopyright © 2011 by the American Society of Agronomy