title: Use of Spectral Radiance to Estimate In-Season Biomass and Grain Yield in Nitrogen- and Water-Stressed Corn.
abstract: Current technologies for measuring plant water status are limited, while recently remote sensing techniques for estimating N status have increased with limited research on the interaction between the two stresses. Because plant water status methods are time-consuming and require numerous observations to characterize a field, managers could benefit from remote sensing techniques to assist in irrigation and N management decisions. A 2-yr experiment was initiated to determine specific wavelengths and/or combinations of wavelengths indicative of water stress and N deficiencies, and to evaluate these wavelengths for estimating in-season biomass and corn (Zea mays L.) grain yield. The experiment was a split-plot design with three replications. The treatment structure had five N rates (0, 45, 90, 134, and 269 kg N ha(-1)) and three water treatments [dryland, 0.5 evapotranspiration (ET), and full ET]. Canopy spectral radiance measurements (350-2500 nm) were taken at various growth stages (V6-V7, V13-V16, and V14-R1). Specific wavelengths for estimating crop biomass, N concentration, grain yield, and chlorophyll meter readings changed with growth stage and sampling date. Changes in total N and biomass in the presence of a water stress were estimated using near-infrared (NIR) reflectance and the water absorption bands. Reflectance in the green and NIR regions were used to estimate total N and biomass without water stress. Reflectance at 510, 705, and 1135 nm were found for estimating chlorophyll meter readings regardless of year or sampling date.
authors.affiliation: USDA-ARS, Northern Grain Insects Research Laboratory, 2923 Medary Ave., Brookings, South Dakota 57006. Dep. of Agronomy and USDA-ARS, Univ. of Nebraska-Lincoln, Lincoln, NE 68583.
authors.forename: S. L.
authors.initials: SL
authors.lastname: Osborne
authors.forename: J. S.
authors.initials: JS
authors.lastname: Schepers
authors.forename: D. D.
authors.initials: DD
authors.lastname: Francis
authors.forename: M. R.
authors.initials: MR
authors.lastname: Schlemmer