Reflectant Induced Modification of Soybean Canopy Radiation Balance. I. Preliminary Tests with a Kaolinite Reflectant1

Abstract ‘Amsoy’ soybeans (Glycine max (L.) Merr.) grown at Mead, Nebraska were coated with kaolinite during 1969 and 1970 to test whether reflection of incident solar radiation can be effectively increased in the field. Increased reflection reduces the amount of radiant energy available and hence reduces the quantity of water consumed by transpiration. Total reflection (300 to 3,000 nm) from the coated crop, measured with an inverted pyranometer, was increased by about 8%. Net radiation was decreased by about 8%. Spectral reflection, measured with a spectroradiometer, was increased primarily in the visible range (380 to 750 nm). Treatment induced differences in reflection were minor in the near infra red range (750 to 1,150 or 1,550 nm). Treatment caused some redistribution of light onto the lower canopy. Results of this preliminary study indicate that the radiation balance of field grown soybeans can be altered by application of reflectant materials.