Hyper-spectral Characteristics And Inversion Modeling Of Leaf And Soil Moisture Of Winter Wheat

Winter wheat is an important food crops, and winter wheat field spectral characteristics has been a focus in the study of plant spectrum. This paper studied the winter wheat hyperspectral characteristics at different growth period and under different irrigation conditions, changes of water content of winter wheat leaves and canopy under different treatment conditions, coverage and leaf area index changes, based on field water control experiment of winter wheat. Finally, the inversion model of the moisture content of the leaves and soil moisture based on hyperspectral remote sensing is established. The conclusions are as follows:1. In the visible band(350 nm-700 nm) maturity stage of winter wheat field spectral reflectance is the largest, In the near infrared wavelengths(760 nm- 1300 nm) maturity stage of winter wheat field spectral reflectance is the minimum. In the near infrared wavelengths(760 nm- 1300 nm), the change of spectral reflectance of winter wheat field during the whole growth period was first increased and then decreased: The spectral reflectance of winter wheat field in regreening and jointing stage is basically the same, the spectral reflectance of winter wheat field in heading and milk-filling stage is basically the same, and significantly increased then jointing stage. The spectral reflectance of winter wheat in the maturity stage of winter wheat was the largest, and then fell sharply.The spectral reflectance of winter wheat field in maturity and regreening stage is basically the same.2. Near infrared short wavelength(760nm~1300nm) is sensitive band. In sensitive wave bands, drought treatment of winter wheat field canopy spectral reflectance increases with the increase of irrigation water after jointing stage. Within a certain range to irrigation water, no drought treatment of winter wheat field canopy spectral reflectance increases with the increase of irrigation water. Beyond a certain range, the winter wheat field canopy spectral reflectance decreases with the increase of irrigation water. The growth period of winter wheat by 80 mm irrigation quota at full grouth stage was prolonged, and the field canopy spectral reflectance characteristics is also lagged.3. Near infrared short wavelength(760nm-1300nm) and heading stage is the winter wheat drought sensitive bands and period. In sensitive bands, if winter wheat field canopy spectral reflectance average value decreased significantly at heading stage, and the late rebound, indicating that winter wheat is in drought after regreening stage. If winter wheat field canopy spectral reflectance average value is the maximum at heading stage, or winter wheat field canopy spectral reflectance average value decreased after jointing stage,indicating that winter wheat is in drought at wintering and regeneration stage.4. The water content of winter wheat leaves and the canopy first increased and then decreased in the full growth stage. The water content of winter wheat canopy reached the maximum at milk-filling stage. Except for the treatment of 80 mm irrigation quota during the whole growth period, the water content of winter wheat leaves was the maximum at heading stage. Under the condition of 80 mm irrigation quota, winter wheat leaf water content decreased significantly in milk-filling stage if winter wheat in drought after jointing stage. It showed that the winter wheat leaf was higher in water sensitivity.5. The cover degree and leaf area index of winter wheat first increased and then decreased along the growth period, and the increase and decrease trend of the leaf area index is greater than the cover degree’s. Winter wheat coverage and leaf area index in milk-filling stage by 80 mm irrigation quota irrigation during whole growth period, all other winter wheat coverage and leaf area index reached the maximum at heading stage, and the maximum of winter wheat cover degree and leaf area index with higher irrigation quota had obvious lag.Under the condition of 80 mm irrigation quota, winter wheat leaf area index decreased significantly in milk-filling stage if winter wheat in drought after jointing stage, it agreed well with the change law of winter wheat leaf water.6. Heading(april 10th) and milk-filling(april 26th) stage is the best monitoring grouth stage of the moisture content of winter wheat leaf, milk-filling stage(april 26th) is the best monitoring grouth stage of the moisture content of soil. Simple ratio water index is the best monitoring index for the moisture content of winter wheat leaves at heading stage, and water index is the best monitoring index for the moisture content of winter wheat leaves and soil at milk-filling stage.