{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,4]],"date-time":"2026-07-04T03:08:02Z","timestamp":1783134482045,"version":"3.54.6"},"reference-count":197,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2020,8,11]],"date-time":"2020-08-11T00:00:00Z","timestamp":1597104000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Recent development of non-destructive optical techniques, such as spectroscopy and machine vision technologies, have laid a good foundation for real-time monitoring and precise management of crop N status. However, their advantages and disadvantages have not been systematically summarized and evaluated. Here, we reviewed the state-of-the-art of non-destructive optical methods for monitoring the N status of crops, and summarized their advantages and disadvantages. We mainly focused on the contribution of spectral and machine vision technology to the accurate diagnosis of crop N status from three aspects: system selection, data processing, and estimation methods. Finally, we discussed the opportunities and challenges of the application of these technologies, followed by recommendations for future work to address the challenges.<\/jats:p>","DOI":"10.3390\/rs12162578","type":"journal-article","created":{"date-parts":[[2020,8,11]],"date-time":"2020-08-11T09:28:57Z","timestamp":1597138137000},"page":"2578","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["Recent Development and Challenges in Spectroscopy and Machine Vision Technologies for Crop Nitrogen Diagnosis: A Review"],"prefix":"10.3390","volume":"12","author":[{"given":"Daoliang","family":"Li","sequence":"first","affiliation":[{"name":"National Innovation Center for Digital Fishery, China Agricultural University, P.O. Box 121, 17 Tsinghua East Road, Beijing 100083, China"},{"name":"Beijing Engineering and Technology Research Centre for Internet of Things in Agriculture China Agriculture University, Beijing 100083, China"},{"name":"China-EU Center for Information and Communication Technologies in Agriculture, China Agriculture University, Beijing 100083, China"},{"name":"Key Laboratory of Agricultural Information Acquisition Technology, Ministry of Agriculture, China Agriculture University, Beijing 100083, China"},{"name":"College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5206-4749","authenticated-orcid":false,"given":"Pan","family":"Zhang","sequence":"additional","affiliation":[{"name":"National Innovation Center for Digital Fishery, China Agricultural University, P.O. Box 121, 17 Tsinghua East Road, Beijing 100083, China"},{"name":"Beijing Engineering and Technology Research Centre for Internet of Things in Agriculture China Agriculture University, Beijing 100083, China"},{"name":"China-EU Center for Information and Communication Technologies in Agriculture, China Agriculture University, Beijing 100083, China"},{"name":"Key Laboratory of Agricultural Information Acquisition Technology, Ministry of Agriculture, China Agriculture University, Beijing 100083, China"},{"name":"College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3941-1603","authenticated-orcid":false,"given":"Tao","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Chemical and Process Engineering, University of Surrey, Guildford GU2 7XH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0860-121X","authenticated-orcid":false,"given":"Wei","family":"Qin","sequence":"additional","affiliation":[{"name":"College of Resources and Environmental Sciences; National Academy of Agricultural Green Development; Key Laboratory of Plant-Soil Interactions, Ministry of Education, China Agricultural University, Beijing 100193, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,8,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1455","DOI":"10.1093\/jxb\/erq425","article-title":"A holistic view of nitrogen acquisition in plants","volume":"62","author":"Kraiser","year":"2011","journal-title":"J. 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