Japanese Journal of Soil Science and Plant Nutrition

The radiocesium interception potential (RIP) was developed as an indicator for frayed edge sites (FES) present in soils and minerals and is widely used to measure soil's ability to retain radiocesium. However, the limiting factors for using RIP to predict radiocesium dynamics in soil have not been adequately investigated. This study aimed to measure RIP using artificially weathered biotite. The solid–liquid partition coefficient (K_d) was determined, and the estimated K_d was calculated using RIP and K⁺ or NH₄⁺ concentrations in the liquid phase. The results consistently showed that the estimated values were lower than the measured values, particularly as the K⁺ or NH₄⁺ concentration in the liquid phase increased. The findings strongly suggest that changes in the swelling state of the solid phase, in combination with the composition of the liquid phase during K_d measurements, play a vital role in the variation of K_d, an aspect that is often overlooked.

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In tea cultivation, excessive use of nitrogen (N) for fertilization can lead to severe soil acidification and environmental pollution due to leaching of N that, in turn, hinders tea plants’ growth. In this study, we investigated the effects of pH neutralization in acidic tea soils using alkaline slag. We applied a mix of blast furnace slag (10, 20％), molten slag (10, 20％), and steelmaking slag (1, 2％) to the tea soils. First-year tea cuttings were planted, and we sampled new tea shoots twice over four months. The findings showed that the application of slag increased the pH of tea soils, with steelmaking slag, blast furnace slag, and then molten slag being the most effective. The growth and quality components of young tea plants remained stable after the application of blast furnace slag and molten slag, but steelmaking slag showed some inhibitory effects. Moreover, the amount of N leaching increased after using blast furnace slag and steelmaking slag, while it decreased after applying molten slag. This suggests that N utilization efficiency improved in young tea plants with molten slag. In conclusion, the application of slag materials can maintain the optimal soil pH range for tea growth, leading to improved growth, quality, and N utilization efficiency of young tea plants. Slag appears to be a useful material for pH neutralization in heavily acidic tea soils.

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