Hyperspectral Reflectance and Their Relationships with Spring Wheat Growth Status Characteristics in Rained Agriculture Areas of Loess Plateau

Diagnosis of crop growth and nutrient status is critical for prediction of agriculture yield and quality at Growth stage. Two experiments, one in 2006 and one in 2007 were conducted to find out spr-wheat canopy and leaf spectral characters nondestructively measurement, and for assessing spring wheat growth status non-destructively at the Experimental Farm (30o53′N, 104o25′E) of Lanzhou University and Dingxi arid meteorology and agriculture experiment station(35°32′N,104°37′E) of CMA, China. The experiment included four cultivars (Heshangtou(a), Gaoyuan602(b), Longchun8139(c) and Dingxi24(d) and seven levels of denesity (D) application in year 2006 and four spring cultivars, four levels of density(D) and three repetition treatments in year 2007. Hyperspectral canopy and leaf reflectance (350–2500 nm) data recorded at various growth stages were measured by an ASD Field Spec Pro FR2500 in different stages, and the contents of Leaf area indices (LAI) of spr-wheat,measured by a LAI2000 plant canopy analyzer, chlorophyll of the leaf, measured by a SPAD502, ground dry biomass, ground fresh biomass and the plant height(PH) to the spectra were determined. The results are following: firstly, the spectral differences are clear for the canopy and leaves of spr-wheat under different density levels, and the canopy spectral reflectance are gradually getting smaller in the visible region and bigger in the near infrared region along with density level increasing at jointing, booting, heading and filling stage, but this change is not evidence at ripening stage; secondly, there are obviously difference in four kinds spr-wheat in canopy and leaf scales spectral reflectance; thirdly, There are “double peak” phenomena for the spr-wheat at nutrition grown stage. Additionally, there were‘blue shift’phenomena for the position of red edge (λred ); Fourthly, the relationship between the spectral vegetation indices and the biochemical parameters indicated that the LAI have the best relationship with DVI and the relativity are the best between the spectral index(λred) and the chlorophyll among the selected spectral index, PVI and FW,plant height (PH) are good correlation. This indicated that some right spectral variables would be used to estimate the LAI, FW, the PH and chlorophyll for sprwheat. Furthermore, the correlation of the spectral index and the biochemical properties of vegetation are effected by the different cultivars.