Studies on Yield-Forecast in Main Crops : 14. Trend of the productivity of paddy rice and its regional classification in the Chugoku district.

Abstract

The regional characteristics were analized from the standpoints of the similarity of yearly fluctuations of yield, the type of grain production and the state of damages of paddy rice in the Chugoku district. Based on the results thus obtained the regional classification of the trend of productivity was given, which may be summarized as follows: 1. The Chugoku district is divided into four regions, the Setouchi region, the mountainous zone, the eastern and western areas of the San-in region, each showing similar variation of yield. 2. The damage percentage in the Chugoku district is only 7-8%. The largest damage is caused by diseases, and the weather damage ranks next. In the San-yo region, the damage by diseases and insects is large. The large weather damage is added to this in Yamaguchi prefecture. The large damage in the eastern area of San-in is due to weather, while in the western area to diseases and insects. 3. Putting all the results together the writers obtain the following regional classification ; the Chugoku district is divided into six regions, that is, the Setouchi littoral zone (high, stable and stagnant yield area), the Suonada littoral zone (low, stable and stagnant Yield area), the Tottori littoral zone (high, stable and stagnant yield area), the Izumo plane zone (high or middle, unstable and increasing yield area), the Iwami littoral zone (middle or low, unstable and increasing yield area), and the Chugoku mountain range zone (middle, unstable and increasing yield area).