Influences of Environmental Factors on Lodging of Wheat and Barley Plants : 2. Wind treatment by mobile wind tunnel and measurements of wind over fields

[摘要] Wind is one of the most important factors which cause lodging. This paper mainly deals with the effect of wind on lodging. Inclined angles and the rates of lodged culms of variously treated plants, such as thinned and leaf- or ear-removed, were measured in a mobile wind tunnel blowing 15m/sec of wind velocity. The measurement of drag force by wind were made with a drag meter (Fig. 1) in the wind tunnel. Winds over wheat and barley fields were observed by small cup anemometers. The shear stress which plant surfaces exerted on wind was calculated by aerodynamical method. Results obtained are as follows: 1. Wind treatment (15 m/sec, 1 hr) were caused lodging. Sekitori-sai no. 1 (barley) lodged because of culm breaking, and Norin no. 61 (wheat) because of culm breaking and bending (Table 1). 2. Lodging was increased by thinning treatment, and the contributions of, various organs of barley to drag force were different from those of wheat, that is, leaves was 20 %, ear 50 % and culm 30 % in barley, and leaved wad 30 %, ear 10 % and culm 60 % in wheat. 3. Both total drag force and the force of unit silhouette area exerted on Hagane-mugi (barley) were higher than those on Norin no. 61 (wheat), because of higher values of silhouette area and drag coefficient (Fig. 2, 4 and 5). Total drag force was related to the third power of wind velocity (Eq. 8), and the force of unit silhouette area was to the second power of wind velocity (Eq. 6) both in the case of wheat and barley. 4. The shear stress obtained by observations of wind was different from the drag force obtained by wind tunnel experiments. But the tendency of the shear stress reported here was in good accord with that of rice fields described by Tani (Fig. 9). 5. It is considered that the discrepancy between the drag force and the shear stress needs further experiments under field and laboratory conditions, and Reynold's similarity theory could afford to solve this problem.

[学科分类] 农业科学（综合）