Risk assessment for radiocesium concentration in brown rice cultivated in paddy field

The following fact has been found. If the radioactive cesium concentration of brown rice in the previous year's crop is unknown due to reasons such as the first planting after the nuclear accident, the soil before fertilization is used to cultivate rice seedlings for 14 days (period from the start of germination until collecting seedlings). By measuring the radioactive cesium concentration of the seedlings, the radioactive cesium concentration of brown rice without potassium application can be predicted. In the future, it will be necessary to study a method for predicting the concentration of radioactive cesium in brown rice when potassium is applied. On the other hand, rice is cultivated in pots with l/10000 a embedded in a paddy field immediately after transplantation, and the exchangeable potassium content and brown rice radioactive cesium concentration in the soil during the maturity period are measured. It is possible to evaluate the risk of decrease in exchangeable potassium content and the risk of increase in the radioactive cesium concentration in brown rice when continuing fertilization with insufficient potassium application for several years. This paper reports the test results of two plots of paddy fields. (A.O.)