{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,20]],"date-time":"2026-03-20T17:00:06Z","timestamp":1774026006617,"version":"3.50.1"},"reference-count":47,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2014,3,31]],"date-time":"2014-03-31T00:00:00Z","timestamp":1396224000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Estimating crop nitrogen (N) status with sensors can be useful to adjust fertilizer levels to crop requirements, reducing farmers\u2019 costs and N losses to the environment. In this study, we evaluated the potential of hyperspectral indices obtained from field data and airborne imagery for developing N fertilizer recommendations in maize (Zea mays L.). Measurements were taken in a randomized field experiment with six N fertilizer rates ranging from zero to 200 kg\u2219N\u2219ha\u22121 and four replications on two different dates (before the second fertilizer application and at flowering) in 2012. Readings at ground level were taken with SPAD\u00ae, Dualex\u00ae and Multiplex\u00ae sensors, and airborne data were acquired by flying a hyperspectral and a thermal sensor 300 m over the experimental site. The hyperspectral imagery was used to calculate greenness, chlorophyll and photochemical indices for each plot. The Pearson coefficient was used to quantify the correlation between sensor readings and agronomic measurements. A statistical procedure based on the  N-sufficient index was used to determine the accuracy of each index at distinguishing between N-deficient and N-sufficient plots. Indices based on airborne measurements were found to be as reliable as measurements taken with ground-level equipment at assessing crop N status and predicting yield at flowering. At stem elongation, the reflectance ratio, R750\/R710, and fluorescence retrieval (SIF760) were the only indices that yielded significant results when compared to crop yield. Field-level SPAD readings, the airborne R750\/R710 index and SIF760 had the lowest error rates when distinguishing N-sufficient from N-deficient treatments, but error reduction is still recommended before commercial field application.<\/jats:p>","DOI":"10.3390\/rs6042940","type":"journal-article","created":{"date-parts":[[2014,3,31]],"date-time":"2014-03-31T10:26:55Z","timestamp":1396261615000},"page":"2940-2962","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":124,"title":["Airborne Hyperspectral Images and Ground-Level Optical Sensors As Assessment Tools for Maize Nitrogen Fertilization"],"prefix":"10.3390","volume":"6","author":[{"given":"Miguel","family":"Quemada","sequence":"first","affiliation":[{"name":"School of Agricultural Engineering, Technical University of Madrid, Avda. Complutense s\/n,  E-28040 Madrid, Spain"}]},{"given":"Jose","family":"Gabriel","sequence":"additional","affiliation":[{"name":"School of Agricultural Engineering, Technical University of Madrid, Avda. Complutense s\/n,  E-28040 Madrid, Spain"}]},{"given":"Pablo","family":"Zarco-Tejada","sequence":"additional","affiliation":[{"name":"Instituto de Agricultura Sostenible (IAS), Consejo Superior de Investigaciones Cient\u00edficas (CSIC), Alameda del Obispo s\/n, E-14004 C\u00f3rdoba, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2014,3,31]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"671","DOI":"10.1038\/nature01014","article-title":"Agricultural sustainability and intensive production practices","volume":"418","author":"Tilman","year":"2002","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"140","DOI":"10.1016\/j.eja.2005.05.005","article-title":"Evaluation of chlorophyll meters as tools for N fertilization in winter wheat under humid Mediterranean conditions","volume":"24","author":"Arregui","year":"2006","journal-title":"Eur. J. Agron"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"800","DOI":"10.2134\/agronj2008.0162Rx","article-title":"Strategies to make use of plant sensors-based diagnostic information for nitrogen recommendations","volume":"101","author":"Samborski","year":"2009","journal-title":"Agron. J"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1051\/agro:2003060","article-title":"Distortion of the SPAD 502 chlorophyll meter readings by changes in irradiance and leaf water status","volume":"24","author":"Guimat","year":"2004","journal-title":"Agronomie"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Schepers, J.S., and Raun, W.R. (2008). Nitrogen in Agricultural Systems, Agronomy Monograph 49, ASA, CSSA, SSSA. Chapter 16.","DOI":"10.2134\/agronmonogr49"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"403","DOI":"10.2134\/agronj1995.00021962008700030003x","article-title":"Use of a chlorophyll meter at the early dent stage of corn to evaluate nitrogen sufficiency","volume":"87","author":"Piekielek","year":"1995","journal-title":"Agron. J"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"69","DOI":"10.21273\/HORTSCI.27.1.69","article-title":"Inherent limitations of nondestructive chlorophyll meters: A comparison of two types of meters","volume":"27","author":"Monje","year":"1992","journal-title":"HortScience"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1663","DOI":"10.1046\/j.1365-3040.2002.00942.x","article-title":"The use of chlorophyll fluorescence excitation spectra for the non-destructive in situ assessment of UV absorbing compounds in leaves","volume":"25","author":"Cerovic","year":"2002","journal-title":"Plant Cell Environ"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1007\/s13593-011-0041-1","article-title":"Sensing crop nitrogen status with fluorescence indicators. A review","volume":"32","author":"Tremblay","year":"2011","journal-title":"Agron. Sustain. Dev"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1046\/j.1461-0248.2001.00192.x","article-title":"The carbon-nutrient balance hypothesis: Its rise and fall","volume":"4","author":"Hamilton","year":"2001","journal-title":"Ecol. Lett"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/j.fcr.2004.05.002","article-title":"Optically assessed contents of leaf polyphenolics and chlorophyll as indicators of nitrogen deficiency in wheat (Triticum. aestivum L.)","volume":"91","author":"Cartelat","year":"2005","journal-title":"Field Crop. Res"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1491","DOI":"10.1109\/36.934080","article-title":"Scaling-up and model inversion methods with narrow-band optical indices for chlorophyll content estimation in closed forest canopies with hyperspectral data","volume":"39","author":"Miller","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1007\/s11119-011-9231-8","article-title":"Normalization of uncalibrated late-season digital aerial imagery for evaluating corn nitrogen status","volume":"13","author":"Kyveryga","year":"2012","journal-title":"Prec. Agric"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1000","DOI":"10.2135\/cropsci2009.04.0203","article-title":"Sensitivities of normalized difference vegetation index and a green\/red ratio index to cotton ground cover fraction","volume":"50","author":"Ritchie","year":"2010","journal-title":"Crop Sci"},{"key":"ref_15","unstructured":"Rouse, J.W., Haas, R.H., Schell, J.A., Deering, D.W., and Harlan, J.C. (1974). Monitoring the Vernal Advancements and Retrogradation of Natural Vegetation, NASA\/GSFC."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"647","DOI":"10.14358\/PERS.69.6.647","article-title":"Remote sensing for crop management","volume":"69","author":"Pinter","year":"2003","journal-title":"Photogramm. Eng. Remote Sens"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1442","DOI":"10.2134\/jeq2002.1442","article-title":"Narrow-waveband reflectance ratios for remote estimation of nitrogen status in cotton","volume":"31","author":"Reed","year":"2002","journal-title":"J. Environ. Qual"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.rse.2011.10.007","article-title":"Fluorescence, temperature and narrowband indices acquired from a UAV platform for water stress detection using a micro-hyperspectral imager and a thermal camera","volume":"117","author":"Berni","year":"2012","journal-title":"Remote Sens. Environ"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1016\/j.rse.2013.02.003","article-title":"Spatio-temporal patterns of chlorophyll fluorescence and physiological and structural indices acquired from hyperspectral imagery as compared with carbon fluxes measured with eddy covariance","volume":"133","author":"Morales","year":"2013","journal-title":"Remote Sens. Environ"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1016\/j.rse.2013.05.011","article-title":"Relationships between net photosynthesis and steady-state chlorophyll fluorescence retrieved from airborne hyperspectral imagery","volume":"136","author":"Catalina","year":"2013","journal-title":"Remote Sens. Environ"},{"key":"ref_21","unstructured":"Soil Survey Staff (2003). Keys to Soil Taxonomy, USDA, Natural Resources Conservation Service. [9th ed.]."},{"key":"ref_22","unstructured":"Papadakis, J. (1966). Climates of the World and Their Agricultural Potentialities, DAPCO."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/j.eja.2010.11.006","article-title":"Replacing bare fallow with cover crops in a maize cropping system: Yield, N uptake and fertiliser fate","volume":"34","author":"Gabriel","year":"2011","journal-title":"Eur. J. Agron"},{"key":"ref_24","unstructured":"Allen, R.G., Pereira, L.S., Raes, D., and Smith, M. (1998). FAO 56 Irrigation and Drainage Paper: Crop Evapotranspiration, Food and Agriculture Organization."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"335","DOI":"10.1007\/s00271-007-0097-5","article-title":"Use of thermal units to estimate corn crop coefficients under semiarid climatic conditions","volume":"26","year":"2008","journal-title":"Irrig. Sci"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"561","DOI":"10.1111\/j.1744-7348.1991.tb04895.x","article-title":"An uniform decimal code for growth stages of crops and weeds","volume":"119","author":"Lancashire","year":"1991","journal-title":"Ann. Appl. Biol"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1449","DOI":"10.21273\/HORTSCI.21.6.1449","article-title":"A rapid and nondestructive method to determine chlorophyll in intact leaves","volume":"21","author":"Yadava","year":"1986","journal-title":"Hortscience"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1355","DOI":"10.1080\/01904160701555689","article-title":"Evaluation of the Dualex for the assessment of corn nitrogen status","volume":"30","author":"Tremblay","year":"2007","journal-title":"J. Plant Nutr"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"722","DOI":"10.1109\/TGRS.2008.2010457","article-title":"Thermal and narrow-band multispectral remote sensing for vegetation monitoring from an unmanned aerial vehicle","volume":"47","author":"Berni","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1016\/0034-4257(94)00114-3","article-title":"Estimating PAR absorbed by vegetation from bidirectional reflectance measurements","volume":"51","author":"Rougean","year":"1995","journal-title":"Remote Sens. Environ"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"416","DOI":"10.1016\/S0034-4257(02)00018-4","article-title":"Integrated narrow-band vegetation indices for prediction of crop chlorophyll content for application to precision agriculture","volume":"81","author":"Haboudane","year":"2002","journal-title":"Remote Sens. Environ"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/0034-4257(92)90059-S","article-title":"A narrow-wave band spectral index that tracks diurnal changes in photosynthetic efficiency","volume":"41","author":"Gamon","year":"1992","journal-title":"Remote Sens. Environ"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1016\/j.rse.2005.09.002","article-title":"Assessing vineyard condition with hyperspectral indices: Leaf and canopy reflectance simulation in a row-structured discontinuous canopy","volume":"99","author":"Miller","year":"2005","journal-title":"Remote Sens. Environ"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1233","DOI":"10.2136\/sssaj1997.03615995006100040032x","article-title":"Ability for in season correction of nitrogen deficiency in corn using chlorophyll meter","volume":"61","author":"Varvel","year":"1997","journal-title":"Soil Sci. Soc. Am. J"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1987","DOI":"10.1016\/j.rse.2010.04.006","article-title":"New spectral indicator assesing the efficiency of crop nitrogen treatment in corn and wheat","volume":"114","author":"Chen","year":"2010","journal-title":"Remote Sens. Environ"},{"key":"ref_36","first-page":"934","article-title":"Light reflectance compared with other nitrogen stress measurements in corn leaves","volume":"6","author":"Blackmer","year":"1996","journal-title":"Agron. J"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1814","DOI":"10.2135\/cropsci2000.4061814x","article-title":"Reflectance indices with precision and accuracy in predicting cotton leaf nitrogen concentration","volume":"40","author":"Tarpley","year":"2002","journal-title":"Crop Sci"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"781","DOI":"10.1071\/AR05361","article-title":"Detection of nitrogen deficiency in wheat from spectral reflectance indices and basic crop eco-physiological concepts","volume":"57","author":"Rodriguez","year":"2006","journal-title":"Aust. J. Agric. Res"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"246","DOI":"10.1016\/0034-4257(94)90020-5","article-title":"Estimating crop water deficit using the relationship between surface air temperature and spectral vegetation index","volume":"46","author":"Moran","year":"1994","journal-title":"Remote Sens. Environ"},{"key":"ref_40","first-page":"1","article-title":"Spectral and thermal sensing for nitrogen and water status in rainfed and irrigated wheat environments","volume":"1","author":"Fitzgerald","year":"2006","journal-title":"Prec. Agric"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"29","DOI":"10.13031\/2013.12546","article-title":"Ground-based remote sensing of water and nitrogen stress","volume":"46","author":"Kostrzewski","year":"2003","journal-title":"Trans. ASAE"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1016\/j.agwat.2007.05.020","article-title":"Ground-based remote sensing for assessing water and nitrogen status of broccoli","volume":"92","author":"Waller","year":"2007","journal-title":"Agric. Water Manag"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"277","DOI":"10.2134\/agronj2007.0187","article-title":"Strategies to improve nitrogen-use efficiency in winter cereal crops under rainfed Mediterranean conditions","volume":"100","author":"Arregui","year":"2008","journal-title":"Agron. J"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.agee.2013.04.018","article-title":"Meta-analysis of strategies to control nitrate leaching in irrigated agricultural systems and their effects on crop yield","volume":"174","author":"Quemada","year":"2013","journal-title":"Agric. Ecosyst. Environ"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"S56","DOI":"10.1016\/j.rse.2008.01.026","article-title":"PROSPECT + SAIL models: A review of use for vegetation characterization","volume":"113","author":"Jacquemoud","year":"2009","journal-title":"Remote Sens. Environ"},{"key":"ref_46","unstructured":"Williams, N. (1987). Near-Infrared Technology in Agriculture and Food Industries, American Association of Cereal Chemists."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1016\/j.compag.2010.05.006","article-title":"Comparative analysis of three chemometric techniques for the spectroradiometric assessment of canopy chlorophyll content in winter wheat","volume":"73","author":"Atzberger","year":"2008","journal-title":"Comput. Electron. Agric"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/6\/4\/2940\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:09:46Z","timestamp":1760216986000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/6\/4\/2940"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,3,31]]},"references-count":47,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2014,4]]}},"alternative-id":["rs6042940"],"URL":"https:\/\/doi.org\/10.3390\/rs6042940","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2014,3,31]]}}}