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Research article - Peer-reviewed, 2022

Estimation of Dry Matter and N Nutrient Status of Choy Sum by Analyzing Canopy Images and Plant Height Information

Wang, Zhao; Shi, Jiang; Sun, Sashuang; Zhu, Lijun; He, Yiyin; Jin, Rong; Luo, Letan; Zhao, Lin; Peng, Junxiang; Zhou, Zhenjiang;


The estimation accuracy of plant dry matter by spectra- or remote sensing-based methods tends to decline when canopy coverage approaches closure; this is known as the saturation problem. This study aimed to enhance the estimation accuracy of plant dry matter and subsequently use the critical nitrogen dilution curve (CNDC) to diagnose N in Choy Sum by analyzing the combined information of canopy imaging and plant height. A three-year experiment with different N levels (0, 25, 50, 100, 150, and 200 kg center dot ha(-1)) was conducted on Choy Sum. Variables of canopy coverage (CC) and plant height were used to build the dry matter and N estimation model. The results showed that the yields of N-0 and N-25 were significantly lower than those of high-N treatments (N-50, N-100, N-150, and N-200) for all three years. The variables of CC x Height had a significant linear relationship with dry matter, with R-2 values above 0.87. The good performance of the CC x Height-based model implied that the saturation problem of dry matter prediction was well-addressed. By contrast, the relationship between dry matter and CC was best fitted by an exponential function. CNDC models built based on CC x Height information could satisfactorily differentiate groups of N deficiency and N abundance treatments, implying their feasibility in diagnosing N status. N application rates of 50-100 kgN/ha are recommended as optimal for a good yield of Choy Sum production in the study region.


Choy Sum; critical nitrogen dilution curve; plant height; canopy coverage; N fertilization

Published in

Remote Sensing

2022, volume: 14, number: 16, article number: 3964
Publisher: MDPI

Authors' information

Wang, Zhao
Zhejiang University
Shi, Jiang
Hangzhou Academy of Agricultural Sciences
Sun, Sashuang
Zhejiang University
Zhu, Lijun
Zhejiang University
He, Yiyin
Zhejiang University
Jin, Rong
Zhejiang University
Letan, Luo
Hangzhou Academy of Agricultural Sciences
Zhao, Lin
Hangzhou Academy of Agricultural Sciences
Swedish University of Agricultural Sciences, Department of Agricultural Research for Northern Sweden
Zhou, Zhenjiang
Zhejiang University

UKÄ Subject classification

Environmental Sciences
Remote Sensing

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