One of the disadvantages of the windbreak is that the windbreak casts shadow on the cultivated field. This paper deals with some investigations concerning the windbreak at Miyazaki City (31°56′N, 131°26′E).
The calculating methods are as follows.
1. Length (L) and direction of the forest-shadow.
Distance (D) from the forest to the top-line of the shadow.
……Fig. I, Formula I) & 2)
2. Time (T) when the shadow retards towards the forest, and the direct sunshine begins to arrive at a certain place. ……Fig. 2.
3. Comparing the duration of sunshine at several places with whole sunshine duration.
4. Comparing the received solar radiation at several places with whole solar radiation.
The loss in receiving solar radiation is marked only in the narrow band neighbouring the windbreak See Fig. 3, Tables I and 2.