PROBLEM TO BE SOLVED: To cultivate Japanese buckwheat, Tartar buckwheat, etc. even with soil pH (H20) of 5.5-8.5 as long as the temperature is 18-26°C when flowering, and to attain rotation cultivation with sugar canes and sweet potatoes which are staple crops of Okinawa Prefecture.SOLUTION: At least one crop selected from a polygonaceae buckwheat family such as Japanese buckwheat and Tartar buckwheat is cultivated in soil with soil pH (H20) adjusted to 5.5-8.5 after adding, to the soil, alkaline earth metal comprising calcium and magnesium, or in soil that shows soil chemical properties of soil pH (H20) of 5.5-8.5, at a temperature of 18-26°C when flowering, and buckwheat flour and buckwheat grains are produced and used as a raw material for confectionery, bread, buckwheat Shochu (distilled spirit) or Miso (fermented soybean paste). Rotation cultivation with sugar canes and sweet potatoes can also be attained.【課題】開花時に１８℃～２６℃の温度下であれば、土壌ｐＨ（Ｈ２０）が５．５～８．５でも日本そばや韃靼そば等を栽培し、沖縄県の基幹作物であるサトウキビや甘藷と輪作栽培可能とする。【解決手段】カルシウムやマグネシウムから成るアルカリ土類金属を土壌に添加し、土壌ｐＨ（Ｈ２０）を５．５～８．５に調整した土壌、又は土壌ｐＨ（Ｈ２０）が５．５～８．５の土壌化学的性質を示す土壌に、日本そば及び韃靼そば等タデ科ソバ属から選ばれる少なくとも１作物を開花時に１８℃～２６℃の温度下で栽培し、そば粉及びそばの実を生産し、菓子・パンやそば焼酎や味噌の原料として利用する。また、サトウキビや甘藷と輪作栽培可能とする。
