{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,20]],"date-time":"2026-06-20T18:27:00Z","timestamp":1781980020559,"version":"3.54.5"},"reference-count":54,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2016,7,19]],"date-time":"2016-07-19T00:00:00Z","timestamp":1468886400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002855","name":"Chinese Ministry of Science and Technology","doi-asserted-by":"publisher","award":["2015CB150405"],"award-info":[{"award-number":["2015CB150405"]}],"id":[{"id":"10.13039\/501100002855","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"Natural Science Foundation of China","doi-asserted-by":"publisher","award":["31421092"],"award-info":[{"award-number":["31421092"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004573","name":"Chinese Ministry of Agriculture","doi-asserted-by":"publisher","award":["2011-G18"],"award-info":[{"award-number":["2011-G18"]}],"id":[{"id":"10.13039\/501100004573","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The nitrogen (N) nutrition index (NNI) is a reliable indicator of crop N status and there is an urgent need to develop efficient technologies for non-destructive estimation of NNI to support the practical applications of precision N management strategies. The objectives of this study were to: (i) validate a newly established critical N dilution curve for spring maize in Northeast China; (ii) determine the potential of using the GreenSeeker active optical sensor to non-destructively estimate NNI; and (iii) evaluate the performance of different N status diagnostic approaches based on estimated NNI via the GreenSeeker sensor measurements. Four field experiments involving six N rates (0, 60, 120,180, 240, and 300 kg\u00b7ha\u22121) were conducted in 2014 and 2015 in Lishu County, Jilin Province in Northeast China. The results indicated that the newly established critical N dilution curve was suitable for spring maize N status diagnosis in the study region. Across site-years and growth stages (V5\u2013V10), GreenSeeker sensor-based vegetation indices (VIs) explained 87%\u201390%, 87%\u201389% and 83%\u201384% variability of leaf area index (LAI), aboveground biomass (AGB) and plant N uptake (PNU), respectively. However, normalized difference vegetation index (NDVI) became saturated when LAI &gt; 2 m2\u00b7m\u22122, AGB &gt; 3 t\u00b7ha\u22121 or PNU &gt; 80 kg\u00b7ha\u22121. The GreenSeeker-based VIs performed better for estimating LAI, AGB and PNU at V5\u2013V6 and V7\u2013V8 than the V9\u2013V10 growth stages, but were very weakly related to plant N concentration. The response index calculated with GreenSeeker NDVI (RI\u2013NDVI) and ratio vegetation index (R2 = 0.56\u20130.68) performed consistently better than the original VIs (R2 = 0.33\u20130.55) for estimating NNI. The N status diagnosis accuracy rate using RI\u2013NDVI was 81% and 71% at V7\u2013V8 and V9\u2013V10 growth stages, respectively. We conclude that the response indices calculated with the GreenSeeker-based vegetation indices can be used to estimate spring maize NNI non-destructively and for in-season N status diagnosis between V7 and V10 growth stages under experimental conditions with variable N supplies. More studies are needed to further evaluate different approaches under diverse on-farm conditions and develop side-dressing N recommendation algorithms.<\/jats:p>","DOI":"10.3390\/rs8070605","type":"journal-article","created":{"date-parts":[[2016,7,19]],"date-time":"2016-07-19T09:48:22Z","timestamp":1468921702000},"page":"605","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":109,"title":["Active Optical Sensing of Spring Maize for In-Season Diagnosis of Nitrogen Status Based on Nitrogen Nutrition Index"],"prefix":"10.3390","volume":"8","author":[{"given":"Tingting","family":"Xia","sequence":"first","affiliation":[{"name":"Key Laboratory of Plant-Soil Interactions, Ministry of Education, International Center for Agro-Informatics and Sustainable Development, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuxin","family":"Miao","sequence":"additional","affiliation":[{"name":"Key Laboratory of Plant-Soil Interactions, Ministry of Education, International Center for Agro-Informatics and Sustainable Development, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dali","family":"Wu","sequence":"additional","affiliation":[{"name":"Key Laboratory of Plant-Soil Interactions, Ministry of Education, International Center for Agro-Informatics and Sustainable Development, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hui","family":"Shao","sequence":"additional","affiliation":[{"name":"Key Laboratory of Plant-Soil Interactions, Ministry of Education, International Center for Agro-Informatics and Sustainable Development, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rajiv","family":"Khosla","sequence":"additional","affiliation":[{"name":"Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guohua","family":"Mi","sequence":"additional","affiliation":[{"name":"Key Laboratory of Plant-Soil Interactions, Ministry of Education, International Center for Agro-Informatics and Sustainable Development, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2016,7,19]]},"reference":[{"key":"ref_1","unstructured":"FAOSTAT Agriculture Database. 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