Spring wheat-leaf phytomass and yield estimates from airborne scanner and hand-held radiometer measurements†

Abstract

Our objective was to relate radiance measurements from a hand-held radiometer (Exotech 100-A) and an airborne muitispectral scanner (Daedalus DEI 1260) to different wheat (Triticum aestiuum L.) stand densities (simulated winter wheat winterkill) and to grain yield. The field experiment was located 11 km north-west of Sidney, Montana (47°45'N, 104°16'W) on a Williams loam soil (fine-loamy, mixed Typic Argiborolls). Three rates—67, 27 and 13 kg/ha—of ‘Len’, a semidwarf, hard red spring-wheat cultivar, were seeded to represent stands of 100, 40 and 20 per cent. Radiances were measured with a hand-held radiometer on clear mornings throughout the growing season. Aircraft overflight measurements were made at three growth stages: tillering, stem extension and heading period The near-IR/red ratio was used in the.analysis. Both aircraft and ground measurements made it possible to differentiate and evaluate wheat stand densities at an early enough growth stage to make management decisions. The aircraft measurements also corroborated hand-held radiometer measurements when related to yield prediction. Although there was some growth dependency, the near-IR/red ratio correlated with yield when measured from just past tillering until about the watery-ripe stage. The results reinforce the potential of remote sensing for estimating grain yields and evaluating winterkill.