2019 Volume 88 Issue 3 Pages 161-167
The cultivation of buckwheat (Fagopyrum esculentum Moench) started recently on northern Okinawa Island and Miyako Island, Japan. The physicochemical properties such as soil organic matter content and phosphorus (P) form of Kunigami Merge, a red acidic soil on northern Okinawa, and Shimajiri Merge, a dark-red neutral soil in Miyako, are very different from those of Andosols (black soil) in the traditional buckwheat cultivation areas in Japan. In this study, we grew buckwheat on these soils in Okinawa, and compared the growth, yield and nutrient uptake on the red soil with those on the black soil. Growth and yield were lower on the red soil than on the black soil due to fewer flowers on the lateral branches and lower seed-set-ratio. The stem and grain N contents were low on the red soil. The stem P content was significantly higher on the red soil, although the grain P content was low. The K content in all parts was the lowest in the dark-red soil, although the stem Ca content was the highest. The Mg content in all parts was the highest in the red soil. The stem weight, grain weight, and the number of lateral branches had significant positive correlations with the soil N and Al-bound P contents, but no correlations with the soil Fe-bound P and available P contents. Low growth and yield on Okinawa soils seemed to be due to the binding of fertilized P with Fe.
