Comparison of mineral contents in polished rice in different cultivation years

Contents of minerals (N, P, K. Mg, Ca, Zn, Mn, Na, Fe and Cu) in polished rice (milled to yields of 90 similar to 91%) grown in various regions of Japan in different cultivation years (1991, 1993 and 1994) were investigated. Rice crops of the same variety grown in the same region in different years were analyzed. The polished rice was digested with nitric acid in a microwave oven, and the mineral contents were then measured with an Inductivity Coupled Plasma Atomic Emission Spectrophotometer (ICP-AES). The mineral content data were divided into groups corresponding to individual minerals and subjected to cluster analysis. One result of this analysis was that, in the N, P and K groups, rice crops with similar crop report indexes were classified into the same cluster. The mineral contents of the rice grown in 1994 differed from those of the rice grown in 1991 and 1993. The agricultural climate in 1991 and 1993 resulted in rice crop report indexes of 95 and 74, respectively, whereas the 1994 index was 109. Therefore, the present results indicate that agricultural climate affects the contents of minerals, especially N, P and K, in polished rice.