PeerJ (Aug 2021)

Recommended nitrogen rates and the verification of effects based on leaf SPAD readings of rice

  • Wenfeng Hou,
  • Juan Shen,
  • Weitao Xu,
  • Muhammad Rizwan Khan,
  • Yin Wang,
  • Xue Zhou,
  • Qiang Gao,
  • Behzad Murtaza,
  • Zhongqing Zhang

DOI
https://doi.org/10.7717/peerj.12107
Journal volume & issue
Vol. 9
p. e12107

Abstract

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Modern rice production systems need a reliable, easy-to-use, efficient, and environmentally-friendly method to determine plant nitrogen (N) status , predict grain yield, and optimize N management. We conducted field experiments to determine the influence of different N rates on Soil Plant Analysis Development (SPAD) readings of rice leaves. We also performed field validations to evaluate the grain yield and N use efficiency under recommended N rates. Our results showed that leaf SPAD readings increased as N rates increased. We applied the recommended N based on the relationships between the N rates and leaf SPAD readings at the tillering and booting stages. The recommended N decreased N rates and improved N use efficiency without sacrificing grain yield. When compared to farmer practices (FP), the recommended N rates of optimization (OPT) decreased by 5.8% and 10.0%, respectively. In comparison with FP, the N agronomic efficiency of OPT increased by 5.8 and 10.0% while the partial factor productivity of N increased by 6.0 and 14.2%, respectively. The SPAD meter may be a reliable tool to analyze the N in rice, estimate real-time N fertilization, and improve N use efficiency.

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