Detection of nitrogen-overfertilized rice plants with leaf positional difference in hyperspectral vegetation index.
The main objective of this work was to compare the applicability of the single leaf (the uppermost leaf L1 and the third uppermost leaf L3) modified simple ratio (mSR(705) index) and the leaf positional difference in the vegetation index between L1 and L3 (mSR(705L1)-mSR(705L3)) in detecting nitrogen (N)-overfertilized rice plants. A field experiment consisting of three rice genotypes and five N fertilization levels (0, 75, 180, 285, and 390 kg N/ha) was conducted at Xiaoshan, Hangzhou, Zhejiang Province, China in 2008. The hyperspectral reflectance (350-2500 nm) and the chlorophyll concentration (ChlC) of L1 and L3 were measured at different stages. The mSR(705L1) and mSR(705L3) indices appeared not to be highly sensitive to the N rates, especially when the N rate was high (above 180 kg N/ha). The mean mSR(705L1)-mSR(705L3) across the genotypes increased significantly (P<0.05) or considerably from 180 to 285 kg N/ha treatment and from 285 to 390 kg N/ha treatment at all the stages. Also, use of the difference (mSR(705L1)-mSR(705L3)) greatly reduced the influence of the stages and genotypes in assessing the N status with reflectance data. The results of this study show that the N-overfertilized rice plants can be effectively detected with the leaf positional difference in the mSR(705) index.
Zhou
Qi-fa
QF
College of Life Sciences, Zhejiang University, Hangzhou 310058, China. zqifa2002@yahoo.com
Liu
Zhan-yu
ZY
Huang
Jing-feng
JF
D005308:Fertilizers; D009584:Nitrogen / Q000008:administration & dosage*; D012275:Oryza / Q000187:drug effects* / Q000254:growth & development*; D018515:Plant Leaves / Q000187:drug effects* / Q000254:growth & development*; D013057:Spectrum Analysis / Q000379:methods
D005308:Fertilizers; D009584:Nitrogen