Abstract
A field survey was carried out from August 2011 to November 2013 in Miyagi prefecture to evaluate the salt removal performance of a rice paddy due to rainfall after tsunami attack.
It was found that (1) Chlorine ion, Cl-, concentration near the soil surface was reached several to hundred times as much as the allowable Cl-concentration of rice planting in August 2011. Consequently, Cl-concentration in the soil up to 100mm below the soil surface remarkably decreased with time. Two years after the tsunami attack, the time variation of Cl-concentration became small in the whole root zone, (2) In the paddy soil attacked by the tsunami with an inundation height, H, of 3.5m or less, it took one year after tsunami attack before total Cl-concentration in the root zone, ∑Cl-decreased to the allowable ∑Cl-of rice planting, ∑Cl-al, (3) Relationships between H and elapsed days reached ∑Cl-al, Dayal, and cumulative rainfall depth for Dayal can be expressed by equations (6) and (9), respectively.
