An experimental investigation of the lodging of wheat

This paper describes an investigation into the fundamental nature of the wheat (Triticum aestivum L.) lodging process, which was carried out to obtain data to help develop a theoretical model of the lodging process. To enable realistic soil/root systems to be investigated in controlled conditions, a portable wind tunnel was constructed that could be placed over crops of various types in various soil conditions. This paper reports a calibration of this wind tunnel against natural conditions and shows that in many respects a good simulation of the natural wind over a crop was achieved, but that the precise structure of the atmospheric turbulence was not fully represented. Measurements of plant characteristics showed significant variations of natural frequency of plant oscillation during the season, and for different levels of crop wetting. Both stem and root lodging were observed within the wind tunnel. The former was found to occur instantaneously, whilst the latter developed over a period of minutes. The damping of individual shoots is shown to be high with damping ratio estimated at 0.08 and to be unaffected by variation in plant types and soil conditions. The plant drag coefficient is determined through strain gauge measurements and is shown to be of the order of unity. Overall the results suggest that the existing theoretical model is adequate in most aspects, but needs to be refined in others, particularly with regard to the progressive failures observed in the root lodging process. (C) 2003 Elsevier B.V. All rights reserved.