Hyperspectral Response And Nutrition Diagnosis Of Maize Leaves Under Different Nitrogen Fertilizer Dose

Maize is widely planted in the world, and its yield has important influence on food security.Nitrogen nutrition, chlorophyll status of maize leaves can be timely, rapidly monitored usinghyperspectral technology, which could be used to guide maize field nitrogen management, improvemaize yield and quality, embody development requirements of modern agriculture. In this thesis, a2-year maize field experiment of nitrogen gradient (N0~N6) was conducted. As the basic researchobjects, spectral response characteristics of maize leaves under many angles (levels, fertilizer dose, leafreflectance mean of per plant, SPAD value) were discussed, and spectral response sensitive areas ofmaize leaves were found. Various spectral parameters were selected to construct prediction models formaize leaf nitrogen contents, SPAD values based on single or the whole growth periods. The mainconclusions of this thesis were as follows:(1) Sensitive areas of maize leaves were found through studies on spectral response of maizeleaves under same fertilizer dose different levels, same levels different fertilizer dose at different growthstages (jointing stage, booting stage, anthesis-silking stage, filling stage and ripening stage). Maizeleaves of lower level or under low nitrogen fertilizer dose are more sensitive to spectral response. Thesensitive areas of maize leaves were in350~760nm visible band (VB) and761~1300nm near infraredband (NIB). Leaf spectral reflectance (LSR) in VB region decreased with the increase of fertilizer dose,and changes of LSR in NIB region were complex, while changes of LSR in1301~2500nm shortwaveinfrared band (SIB) were minor.Under the same fertilizer level, differences among leaf reflectance means (LRM) of per plant atfive growth stages were all obvious, sensitive areas were in VB, NIB regions, and the differencesdecreased with the increase of fertilizer dose. In VB region, LSR decreased with increase of SPADinterval values at five growth stages. Under the same SPAD interval value, changes of LSR at fivegrowth stages were different.(2) Prediction models for maize leaf nitrogen contents (LNC), SPAD values were constructedbased on data of a single growth stage (jointing stage, booting stage, anthesis-silking stage, filling stageand ripening stage). LNC, SPAD values were extremely significantly negatively correlated with LSR inpart of VB and SIB regions. LNC, SPAD values could be effectively predicted using prediction modelsbased on dissimilarity spectral index (DSI).(3) Prediction models for maize leaf nitrogen contents (LNC), SPAD values were constructedbased on data of the whole growth stages (2011,2012, two-year). The mean curves of LSR or its firstderivative, the correlation coefficient curves of LNC and LSR, SPAD values and LSR or its firstderivative were basically the same, while the correlation coefficient curves of LNC and first derivativewere different. Prediction models built with spectral parameters based on first derivative were unstable,LNC could be effectively predicted using models built with DSI (R550around, R680around) and DSI (R680around,R710around), maize leaf SPAD values could be accurately predicted using model built with LCI, DSI (R550around, R680around) and DSI (R680around, R710around).(4) Sensitive areas of maize ear leaves were in VB and NIB regions, and leaf SPAD values wereextremely significantly negatively correlated with LSR in part of VB and SIB regions. Evaluation andstability of prediction models built with LCI, DSI (678,717) and DSI (549,678) were good, thereforeleaf SPAD values could be accurately predicted.(5) Overall, spectral response sensitive areas of maize leaves were in VB and NIB regions underdifferent nitrogen fertilizer dose. LNC, SPAD values were extremely significantly negatively correlatedwith LSR in VB region, and the two maxima of correlation coefficients were in this region. The bestprediction models were all built with spectral parameters DSI (R550around, R680around) and DSI (R680around,R710around). Therefore, the VB region should be mainly studied when crop nitrogen, chlorophyll statuswere monitored using hyperspectral remote sensing technology, and which can provide experiment datafor developing low-cost, high-precision portable spectroscopy diagnosis instruments.