title: Estimation of wheat agronomic parameters using new spectral indices.
abstract: Crop agronomic parameters (leaf area index (LAI), nitrogen (N) uptake, total chlorophyll (Chl) content ) are very important for the prediction of crop growth. The objective of this experiment was to investigate whether the wheat LAI, N uptake, and total Chl content could be accurately predicted using spectral indices collected at different stages of wheat growth. Firstly, the product of the optimized soil-adjusted vegetation index and wheat biomass dry weight (OSAVI×BDW) were used to estimate LAI, N uptake, and total Chl content; secondly, BDW was replaced by spectral indices to establish new spectral indices (OSAVI×OSAVI, OSAVI×SIPI, OSAVI×CIred edge, OSAVI×CIgreen mode and OSAVI×EVI2); finally, we used the new spectral indices for estimating LAI, N uptake, and total Chl content. The results showed that the new spectral indices could be used to accurately estimate LAI, N uptake, and total Chl content. The highest R(2) and the lowest RMSEs were 0.711 and 0.78 (OSAVI×EVI2), 0.785 and 3.98 g/m(2) (OSAVI×CIred edge) and 0.846 and 0.65 g/m(2) (OSAVI×CIred edge) for LAI, nitrogen uptake and total Chl content, respectively. The new spectral indices performed better than the OSAVI alone, and the problems of a lack of sensitivity at earlier growth stages and saturation at later growth stages, which are typically associated with the OSAVI, were improved. The overall results indicated that this new spectral indices provided the best approximation for the estimation of agronomic indices for all growth stages of wheat.
authors.affiliation: Institute of Crop Science, Chinese Academy of Agricultural Sciences/Key Laboratory of Crop Physiology and Production Ministry of Agriculture, Beijing, China ; Beijing Research Center for Information Technology in Agriculture, Beijing, China.
authors.forename: Xiu-liang
authors.initials: XL
authors.lastname: Jin
authors.forename: Wan-ying
authors.initials: WY
authors.lastname: Diao
authors.forename: Chun-hua
authors.initials: CH
authors.lastname: Xiao
authors.forename: Fang-yong
authors.initials: FY
authors.lastname: Wang
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.forename: Ke-ru
authors.initials: KR
authors.lastname: Wang
authors.forename: Shao-kun
authors.initials: SK
authors.lastname: Li
mesh_terms: D000383:Agriculture; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology; D018515:Plant Leaves / Q000033:anatomy & histology / Q000187:drug effects; D015203:Reproducibility of Results; D012987:Soil; D013057:Spectrum Analysis; D014908:Triticum / Q000187:drug effects / Q000254:growth & development*
chemical_list: D012987:Soil; D002734:Chlorophyll; D009584:Nitrogen
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