Effect of simulated dew on fallout retention and beta radiation damage to a bean crop

A beta-emitting fallout simulant (very fine sand labeled with varying levels of ⁹⁰Y) was applied to a field bean crop Phaseolus vulgaris L.). The foliage was wet or dry in alternate rows at time of application, thus simulating presence or absence of dew conditions. The presence of moisture caused a much larger initial retention of the simulant by the foliage. Dosimetry indicated that the contact dose under moist conditions was substantial, with the wet plants receiving a total dose 60 per cent greater than the dry plants. The yield of string beans was very sensitive to beta radiation and a dose of about 1000 rads to the surface of the apical buds severely reduced the string bean yield. It was estimated that this corresponded to a dose of about 400 rads to the meristematic tissue of these buds. Vegetative growth was much more resistant to the radiation with serious vegetative yield reductions occurring at about 10,000 rads to the surface of the apical buds.