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Volume 15
Issue 17
10.3390/agriculture15171861
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Leaf Color Chart-Based Nitrogen Management Affects Rice Enzyme Activities and Maintains Soil Nitrogen Balance

by
Jichao Tang
1,2,3,
Wenxuan Zhang
1,
Xi Niu
1,
Chengfang Li
2,
Cougui Cao
2,
Dongliang Xiong
2,
Ying Zhang
1,
Jianhua Qu
1,
Bin Wang
4 and
Tianqi Liu
1,2,*
1
School of Resources and Environment, Northeast Agricultural University, Harbin 150030, China
2
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science & Technology, Huazhong Agricultural University, Wuhan 430070, China
3
Wuhan Tanhe International Technology Co., Ltd., Wuhan 430075, China
4
Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(17), 1861; https://doi.org/10.3390/agriculture15171861
Submission received: 12 July 2025 / Revised: 21 August 2025 / Accepted: 27 August 2025 / Published: 31 August 2025
(This article belongs to the Special Issue Innovative Conservation Cropping Systems and Practices—2nd Edition)
Versions Notes

Abstract

Real-time nitrogen (N) management based on the leaf color chart (LCC) is considered a potential alternative to traditional farmer practices. However, its physiological mechanisms for enhancing rice N utilization and its effects on paddy field N balance remain unclear. We aimed to elucidate the potential enzymatic mechanisms underlying LCC’s influence on rice N use and quantify the impact of LCC on paddy field N balance. In 2022 and 2023, a single-factor randomized block design experiment was conducted during the rice planting season. Four N treatments: no N (ONF), farmers’ conventional practices + urea [FNR] as the control, LCC + urea [SSNM1], LCC + controlled-release urea [SSNM2] were administered. Rice yield and N uptake were positive correlations with nitrate reductase (NR), glutamine synthetase (GS), glutamate-pyruvate transaminase (GPT), glutamate-oxaloacetate transaminase (GOT) and glutamate dehydrogenase (GDH) activities, which were higher under SSNM1 and SSNM2 compared with FNR, but were negative correlation with proteinase activity. Moreover, SSNM1 and SSNM2 increased rice yield by 9.2% and 9.4%, N uptake by 15.4% and 15.3%, and N use efficiency by 46.9% and 65.0%, and reduced reactive N losses by 46.2% and 66.7%, respectively. The annual net soil N inputs under FNR, SSNM1, and SSNM2 were 12.6, 8.9, and 4.2 kg N ha–1, respectively. LCC-based N management increased N uptake and rice yield by enhancing the activities of NR, GS, GPT, GOT, and GDH while reducing protease activity. Moreover, LCC maintained soil N supply capacity even with reduced nitrogen fertilizer application.
Keywords: leaf color chart; nitrogen fertilizer; reactive nitrogen losses; nitrogen balance; enzyme activity leaf color chart; nitrogen fertilizer; reactive nitrogen losses; nitrogen balance; enzyme activity

Share and Cite

MDPI and ACS Style

Tang, J.; Zhang, W.; Niu, X.; Li, C.; Cao, C.; Xiong, D.; Zhang, Y.; Qu, J.; Wang, B.; Liu, T. Leaf Color Chart-Based Nitrogen Management Affects Rice Enzyme Activities and Maintains Soil Nitrogen Balance. Agriculture 2025, 15, 1861. https://doi.org/10.3390/agriculture15171861

AMA Style

Tang J, Zhang W, Niu X, Li C, Cao C, Xiong D, Zhang Y, Qu J, Wang B, Liu T. Leaf Color Chart-Based Nitrogen Management Affects Rice Enzyme Activities and Maintains Soil Nitrogen Balance. Agriculture. 2025; 15(17):1861. https://doi.org/10.3390/agriculture15171861

Chicago/Turabian Style

Tang, Jichao, Wenxuan Zhang, Xi Niu, Chengfang Li, Cougui Cao, Dongliang Xiong, Ying Zhang, Jianhua Qu, Bin Wang, and Tianqi Liu. 2025. "Leaf Color Chart-Based Nitrogen Management Affects Rice Enzyme Activities and Maintains Soil Nitrogen Balance" Agriculture 15, no. 17: 1861. https://doi.org/10.3390/agriculture15171861

APA Style

Tang, J., Zhang, W., Niu, X., Li, C., Cao, C., Xiong, D., Zhang, Y., Qu, J., Wang, B., & Liu, T. (2025). Leaf Color Chart-Based Nitrogen Management Affects Rice Enzyme Activities and Maintains Soil Nitrogen Balance. Agriculture, 15(17), 1861. https://doi.org/10.3390/agriculture15171861

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