{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T17:36:32Z","timestamp":1778607392524,"version":"3.51.4"},"reference-count":24,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2022,8,15]],"date-time":"2022-08-15T00:00:00Z","timestamp":1660521600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Key Research and Development Program of China","award":["2019YFE0125500-02"],"award-info":[{"award-number":["2019YFE0125500-02"]}]},{"name":"National Key Research and Development Program of China","award":["2019B020216001"],"award-info":[{"award-number":["2019B020216001"]}]},{"name":"Science and Technology Department of Guangdong Province","award":["2019YFE0125500-02"],"award-info":[{"award-number":["2019YFE0125500-02"]}]},{"name":"Science and Technology Department of Guangdong Province","award":["2019B020216001"],"award-info":[{"award-number":["2019B020216001"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>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\u2219ha\u22121) 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 N0 and N25 were significantly lower than those of high-N treatments (N50, N100, N150, and N200) for all three years. The variables of CC \u00d7 Height had a significant linear relationship with dry matter, with R2 values above 0.87. The good performance of the CC \u00d7 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 \u00d7 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\u2013100 kgN\/ha are recommended as optimal for a good yield of Choy Sum production in the study region.<\/jats:p>","DOI":"10.3390\/rs14163964","type":"journal-article","created":{"date-parts":[[2022,8,15]],"date-time":"2022-08-15T23:44:03Z","timestamp":1660607043000},"page":"3964","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Estimation of Dry Matter and N Nutrient Status of Choy Sum by Analyzing Canopy Images and Plant Height Information"],"prefix":"10.3390","volume":"14","author":[{"given":"Zhao","family":"Wang","sequence":"first","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Huanan Industrial Technology Research Institute of Zhejiang University, Guangzhou 510700, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture and Rural Affairs, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jiang","family":"Shi","sequence":"additional","affiliation":[{"name":"Hangzhou Academy of Agricultural Sciences, Hangzhou 310024, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sashuang","family":"Sun","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Huanan Industrial Technology Research Institute of Zhejiang University, Guangzhou 510700, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture and Rural Affairs, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lijun","family":"Zhu","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Huanan Industrial Technology Research Institute of Zhejiang University, Guangzhou 510700, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture and Rural Affairs, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yiyin","family":"He","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Huanan Industrial Technology Research Institute of Zhejiang University, Guangzhou 510700, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture and Rural Affairs, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rong","family":"Jin","sequence":"additional","affiliation":[{"name":"Agricultural Experiment Station, Zhejiang University, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Letan","family":"Luo","sequence":"additional","affiliation":[{"name":"Hangzhou Academy of Agricultural Sciences, Hangzhou 310024, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lin","family":"Zhao","sequence":"additional","affiliation":[{"name":"Hangzhou Academy of Agricultural Sciences, Hangzhou 310024, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Junxiang","family":"Peng","sequence":"additional","affiliation":[{"name":"Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhenjiang","family":"Zhou","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Huanan Industrial Technology Research Institute of Zhejiang University, Guangzhou 510700, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture and Rural Affairs, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,8,15]]},"reference":[{"key":"ref_1","unstructured":"Kok, P.T., Keng, H., Avadhani, P., and Foo, J.T. (1991). Guide to Common Vegetables, Singapore Science Centre."},{"key":"ref_2","first-page":"1219","article-title":"Effects of nitrogen fertilizer application rate on nitrogen use efficiency and grain yield and quality of different rice varieties","volume":"28","author":"Cong","year":"2017","journal-title":"J. Appl. Ecol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"922","DOI":"10.2134\/agronj2015.0435","article-title":"Designing corn management strategies for high yield and high nitrogen use efficiency","volume":"108","author":"Guo","year":"2016","journal-title":"Agron. J."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Lemaire, G., Plenet, D., and Grindlay, D. (1997). Leaf N content as an indicator of crop N nutrition status. Diagnosis of the Nitrogen Status in Crops, Springer.","DOI":"10.1007\/978-3-642-60684-7_11"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Greenwood, D., Neeteson, J., and Draycott, A. (1986). Quantitative relationships for the dependence of growth rate of arable crops on their nitrogen content, dry weight and aerial environment. Fundamental, Ecological and Agricultural Aspects of Nitrogen Metabolism in Higher Plants, Springer.","DOI":"10.1007\/978-94-009-4356-8_55"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"614","DOI":"10.1016\/j.eja.2008.01.005","article-title":"Diagnosis tool for plant and crop N status in vegetative stage: Theory and practices for crop N management","volume":"28","author":"Lemaire","year":"2008","journal-title":"Eur. J. Agron."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1093\/oxfordjournals.aob.a088118","article-title":"Growth rate and% N of field grown crops: Theory and experiments","volume":"67","author":"Greenwood","year":"1991","journal-title":"Ann. Bot."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1016\/j.fcr.2013.03.012","article-title":"Development of critical nitrogen dilution curve of Japonica rice in Yangtze River Reaches","volume":"149","author":"Yao","year":"2013","journal-title":"Field Crops Res."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1007\/s42106-018-0009-z","article-title":"Localization of maize critical N curve and estimation of NNI by chlorophyll","volume":"12","author":"Liang","year":"2018","journal-title":"Int. J. Plant Prod."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"13084","DOI":"10.1038\/s41598-020-70065-3","article-title":"Construction of a critical nitrogen dilution curve for maize in Southwest China","volume":"10","author":"Du","year":"2020","journal-title":"Sci. Rep."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1016\/j.fcr.2016.08.032","article-title":"A critical nitrogen dilution curve for japonica rice based on canopy images","volume":"198","author":"Wang","year":"2016","journal-title":"Field Crops Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2244","DOI":"10.1080\/00103624.2020.1822376","article-title":"Determination of Critical Nitrogen Dilution Curve Based on Canopy Cover Data for Summer Maize","volume":"51","author":"Ranjbar","year":"2020","journal-title":"Commun. Soil Sci. Plant Anal."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1016\/j.fcr.2018.09.005","article-title":"Determination of critical nitrogen concentration and dilution curve based on leaf area index for summer maize","volume":"228","author":"Zhao","year":"2018","journal-title":"Field Crops Res."},{"key":"ref_14","first-page":"66","article-title":"Critical nitrogen dilution curve of drip-irrigated maize at vegetative growth stage based on leaf area index","volume":"36","author":"Jia","year":"2020","journal-title":"Nongye Gongcheng Xuebao"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"379","DOI":"10.2134\/agronj2013.0213","article-title":"New critical nitrogen curve based on leaf area index for winter wheat","volume":"106","author":"Zhao","year":"2014","journal-title":"Agron. J."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"108139","DOI":"10.1016\/j.fcr.2021.108139","article-title":"A new canopy chlorophyll index-based paddy rice critical nitrogen dilution curve in eastern China","volume":"266","author":"Zhang","year":"2021","journal-title":"Field Crops Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1006\/anbo.1994.1133","article-title":"Determination of a critical nitrogen dilution curve for winter wheat crops","volume":"74","author":"Justes","year":"1994","journal-title":"Ann. Bot."},{"key":"ref_18","first-page":"101","article-title":"Simultaneous effects of water and nitrogen stress on the vegetative and yield parameters of choy sum (Brassica chinensis var. parachinensis)","volume":"39","author":"Khairun","year":"2016","journal-title":"Pertanika J. Trop. Agric. Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"406","DOI":"10.3389\/fpls.2018.00406","article-title":"Water stress scatters nitrogen dilution curves in wheat","volume":"9","author":"Hoogmoed","year":"2018","journal-title":"Front. Plant Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"271","DOI":"10.2134\/agronj2007.0059","article-title":"Critical nitrogen curve and nitrogen nutrition index for corn in eastern Canada","volume":"100","author":"Ziadi","year":"2008","journal-title":"Agron. J."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1016\/j.compag.2011.09.005","article-title":"Assessment of forage mass from grassland swards by height measurement using an ultrasonic sensor","volume":"79","author":"Fricke","year":"2011","journal-title":"Comput. Electron. Agric."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Batistoti, J., Marcato Junior, J., \u00cdtavo, L., Matsubara, E., Gomes, E., Oliveira, B., Souza, M., Siqueira, H., Salgado Filho, G., and Akiyama, T. (2019). Estimating pasture biomass and canopy height in Brazilian savanna using UAV photogrammetry. Remote Sens., 11.","DOI":"10.3390\/rs11202447"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1016\/0304-4238(90)90063-K","article-title":"The effect of nitrogenous fertilizer and plant spacing on the yield of three Chinese vegetables\u2014Kai lan, Tsoi sum and Pak choi","volume":"45","author":"Hill","year":"1990","journal-title":"Sci. Hortic."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"814","DOI":"10.1016\/S1002-0160(17)60392-8","article-title":"A new critical nitrogen dilution curve for rice nitrogen status diagnosis in Northeast China","volume":"28","author":"Huang","year":"2018","journal-title":"Pedosphere"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/16\/3964\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:08:57Z","timestamp":1760141337000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/16\/3964"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,8,15]]},"references-count":24,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2022,8]]}},"alternative-id":["rs14163964"],"URL":"https:\/\/doi.org\/10.3390\/rs14163964","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,8,15]]}}}