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:10.7717/peerj.12107

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

PeerJ. 2021 Aug 26:9:e12107. doi: 10.7717/peerj.12107. eCollection 2021.

Authors

Wenfeng Hou¹, Juan Shen¹, Weitao Xu¹, Muhammad Rizwan Khan², Yin Wang¹, Xue Zhou¹, Qiang Gao¹, Behzad Murtaza³, Zhongqing Zhang¹

Affiliations

¹ Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases/College of Resources and Environmental Science, Jilin Agricultural University, Changchun, Jilin, Changchun, China.
² Soil and Environmental Sciences Division, Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad, Pakistan.
³ Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus, Vehari, Pakistan.

Abstract

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.

Keywords: Chlorophyll; Leaf greenness; Nitrogen diagnosis; Non-destructive; SPAD reading.

Grants and funding

This work was supported by the Scientific Research Start-up Fund of Jilin Agricultural University (202023330); the National Key Research and Development Program of China (2016YFD0200101); and the Science and Technology Project of the 13th Five-Year Plan of Jilin Provincial Department of Education (JJKH20190908KJ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.