Reduction of Soil Fertility by Decontamination and Efforts for Its Recovery (1^st report)

<p>Agricultural soil contaminated with radioactive materials due to the Tokyo Electric Power Company's (Tepco's) Fukushima Daiichi Nuclear Power Station accident was mainly decontaminated by topsoil removal and soil dressing. These processes may adversely affect fertility of agricultural soil. We conducted a research in farmer's yard in Yamakiya district, Fukushima Prefecture:1. to elucidate the effects of decontamination and 2. to restore soil fertility using three types of green manures for 2 years. As a result, 1. a significant decrease in total carbon and nitrogen content, available nitrogen content, and cation exchange capacity in the soil was observed due to the decontamination. Fertility decrease was more remarkable in paddy fields than in vegetable fields. 2. Rye grew vigorously as compared to hairy vetch and sorghum. The mass loss rate of rye and hairy vetch, measured using litter bag for 9 month, was 66 % and 83 %, respectively. Approximately 20 % of input C by green manures remained in soil after 9 months, and the carbon sequestration in soil is also an important aspect of this trial. Rye incorporation significantly increased easily decomposable carbon amount and soluble total nitrogen. Hairy vetch incorporation significantly increased soluble total nitrogen and soil microbial biomass. Fertility recovery for long-term in this region is extremely important. Green manure application may be useful to recover soil microbial available carbon and nitrogen, and it helps to recovery nutrient cycling.</p>