Frontiers in Plant Science (Feb 2020)

Diagnosis of Nitrogen Nutrition in Rice Leaves Influenced by Potassium Levels

  • Wenfeng Hou,
  • Merle Tränkner,
  • Jianwei Lu,
  • Jinyao Yan,
  • Siyuan Huang,
  • Tao Ren,
  • Rihuan Cong,
  • Xiaokun Li

DOI
https://doi.org/10.3389/fpls.2020.00165
Journal volume & issue
Vol. 11

Abstract

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Evaluation of nitrogen (N) status by leaf color is a kind of classic nutritional diagnostic method. However, the color of leaves is influenced not only by N, but also by other nutrients such as potassium (K). Two-year field trials with a factorial combination of N and K were conducted to investigate the effects of different N and K rates on soil plant analysis development (SPAD) readings and leaf N, K, magnesium (Mg), and chlorophyll concentrations. Visual inspections in leaf greenness revealed darker green leaves with increasing N rates, while paler green leaves with increasing K rates. Data showed that SPAD readings, chlorophyll, N and Mg concentrations, and the chloroplast area increased significantly with raising N rates, while declined sharply with the increase in K rates due to the antagonistic relationships between K+ and NH4+ as well as Mg2+. It was also probable that the increase in K promoted the growth of leaves and diluted their N and Mg concentrations. The paler leaf appearance resulting from the application of K may overestimate the actual demand for N in the diagnosis of rice N status. The strong antagonistic relationships between K+, NH4+, and Mg2+ should be considered in rice production and fertilization.

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