Study on chlorophyll meter-based variable rate fertilizer application and influence on winter wheat Nitrogen rate and timing considerations on yield and physiological parameters of corn canopy Effect on Growth and Development, Yield and Water Use Efficiency of Winter Wheat through Controlled-release Urea Base and Common Urea with Split Application in Loess Plateau East of Gansu Genetic Effects and Diagnosis of Premature Senescence of Leaf in Upland Cotton Estimation of Chlorophyll and Nitrogen Contents in Cotton Leaves Using Digital Camera and Imaging Spectrometer Evaluation of SPAD and Dualex for In-Season Corn Nitrogen Status Estimation