THE RELATION BETWEEN REFLECTED RADIATION AND YIELD ON THE BROADBALK WINTER-WHEAT EXPERIMENT

In the classical experiment on Broadbalk field, Rothamsted, winter wheat has been grown continuously under various treatments since 1843. Reflected radiation in red (R) and near-infrared (NIR) wavebands was measured over the field in 1987, twice with an airborne multispectral scanner (MSS) from an altitude of 600m and five times with a multiband radiometer from 2 m above the crop surface. The normalized difference vegetation index, NDVT=(NIR-R)/(NIR + R), was calculated for each date and its relation with harvest yield investigated. The NDVI determined from the airborne MSS data was correlated with yield, and the correlation was found to increase if the variable effect of productivity was introduced into the relationship. The NDVI values calculated from the ground radiometry were more strongly correlated with yield, however. The differences in yield on Broadbalk are caused mainly by the amounts of nitrogen-containing fertilizer applied. The results suggest that the radiation measured by airborne MSS can give a rough guide to yield and nitrogen nutrition, whereas ground radiometry could be used to predict yield and potential deficiencies of nitrogen. © 1990 Taylor & Francis Group, LLC.