Zhao Ben, Zhang Yonghui, Duan Aiwang, Liu Zhandong, Xiao Junfu, Liu Zugui, Qin Anzhen, Ning Dongfeng, Li Sen, Ata-Ul-Karim Syed Tahir
Key Laboratory of Crop Water Use and Regulation, Ministry of Agriculture, Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences, Xinxiang, China.
School of Computer Engineering, Weifang University, Weifang, China.
Front Plant Sci. 2021 Apr 8;12:619522. doi: 10.3389/fpls.2021.619522. eCollection 2021.
The non-destructive estimation of plant nitrogen (N) status is imperative for timely and in-season crop N management. The objectives of this study were to use canopy cover (CC) to establish the empirical relations between plant growth indices [shoot dry matter (SDM), leaf area index (LAI), shoot N accumulation (SNA), shoot nitrogen concentration (SNC)], and CC as well as to test the feasibility of using CC to assess N nutrition index (NNI) from Feekes 3 to Feekes 6 stages of winter wheat. Four multi-locational (2 sites), multi-cultivars (four cultivars), and multi-N rates (0-300 kg N ha) field experiments were carried out during 2016 to 2018 seasons. The digital images of the canopy were captured by a digital camera from Feekes 3 to Feekes 6 stages of winter wheat, while SDM, LAI, SNA, and SNC were measured by destructive plant sampling. CC was calculated from digital images developed by self-programmed software. CC showed significant correlations with growth indices (SDM, LAI, and SNA) across the different cultivars and N treatments, except for SNC. However, the stability of these empirical models was affected by cultivar characteristics and N application rates. Plant N status of winter wheat was assessed using CC through two methods (direct and indirect methods). The direct and indirect methods failed to develop a unified linear regression to estimate NNI owing to the high dispersion of winter wheat SNC during its early growth stages. The relationships of CC with SDM, SNC and NNI developed at individual growth stages of winter wheat using both methods were highly significant. The relationships developed at individual growth stages did not need to consider the effect of N dilution process, yet their stability is influenced by cultivar characteristics. This study revealed that CC has larger limitation to be used as a proxy to manage the crop growth and N nutrition during the early growth period of winter wheat despite it is an easily measured index.
植物氮素（N）状况的无损估测对于适时进行季中作物氮素管理至关重要。本研究的目的是利用冠层覆盖度（CC）建立植物生长指标[地上部干物质（SDM）、叶面积指数（LAI）、地上部氮积累量（SNA）、地上部氮浓度（SNC）]与CC之间的经验关系，并测试在冬小麦从拔节期到孕穗期利用CC评估氮营养指数（NNI）的可行性。在2016至2018年季开展了四项多地点（2个地点）、多品种（4个品种）和多施氮量（0 - 300 kg N ha）的田间试验。在冬小麦从拔节期到孕穗期，用数码相机拍摄冠层的数字图像，同时通过破坏性植株采样测定SDM、LAI、SNA和SNC。CC由自编软件处理数字图像计算得出。除SNC外，CC与不同品种和施氮处理下的生长指标（SDM、LAI和SNA）均表现出显著相关性。然而，这些经验模型的稳定性受品种特性和施氮量的影响。通过两种方法（直接法和间接法）利用CC评估冬小麦的植株氮素状况。由于冬小麦生长早期SNC离散度高，直接法和间接法均未能建立统一的线性回归方程来估算NNI。利用这两种方法在冬小麦各生长阶段建立的CC与SDM、SNC和NNI之间的关系均极显著。在各生长阶段建立的关系无需考虑氮稀释过程的影响，但其稳定性受品种特性影响。本研究表明，尽管CC是一个易于测量的指标，但在冬小麦生长早期将其用作管理作物生长和氮营养的替代指标存在较大局限性。
