Achat,D.L., Augusto,L., Gallet-Budynek,A. and Bakker,M.R.(2012): Drying-induced changes in phosphorus status of soils with contrasting soil organic matter contents - Implications for laboratory approaches. Geoderma, 187-188, 41-48.

『対照的な土壌有機物成分を伴う土壌のリン状態における乾燥由来の変化−実験室でのアプローチとの関係』

『Abstract
　Phosphorus (P) fractions are commonly assessed on dried soils in environmental and long-term field research, because this is the most convenient method of storing large quantities of samples before analysis. However sample pre-treatment may seriously affect the results, especially those regarding the organic P fractions. The objective of the present study was to assess the effect of soil drying under laboratory conditions on the P status of soils with contrasting physico-chemical and microbial properties. We used soils from a (Pinus pinaster) forest in southwest France sampled from different soil depths and different site classes featuring a gradient of soil organic matter (SOM), and aluminium (Al) and iron (Fe) oxides. Total P, total organic and inorganic P, water soluble phosphate ions (iP), microbial P and the potentially mineralizable P in ‘dead’ organic matter were determined on fresh, moist soils maintained at 4℃ and on the same soils, oven-dried at 60℃. Laboratory-drying resulted in a general decrease in total organic P, which was positively correlated with microbial P and SOM content. These drying-induced changes in total organic P were associated with a concomitant increase in total inorganic P and water soluble iP, which were dramatic in the organic forest floor samples (on average + 2965％ (×31 increase) in total inorganic P, and +11880％ (×123 increase) in water soluble iP). The changes in water soluble iP were correlated with the SOM: Al and Fe oxides ratio and showed little effect of soil drying in deeper soil layers with a low SOM and high oxide contents. Our results indicated that soil drying mainly resulted in the lysis of the microbial pool, and to a much lesser extent, in the physical disruption and mineralization of the SOM. We conclude that soil drying before analyses can generate a significant bias in the evaluation of soil P stocks and fluxes, especially in SOM-rich layers. We recommend that fresh soil samples should be used as far as possible to determine soil P status.

Keywords: Microbial P; Water soluble phosphate ions; Soil drying; Soil organic matter; Surface and deep forest soils; Total organic P』

1. Introduction
2. Materials and methods
　2.1. Study sites and soil preparation
　2.2. Phosphorus status
　2.3. Soil properties
　2.4. Data processing and statistics
3. Results
　3.1. Soil moisture
　3.2. Drying-induced changes in total organic P
　3.3. Drying-induced changes in water soluble iP
　3.4. Nutritional implications
4. Discussion
　4.1. Drying-induced changes in P status
　4.2. Effects of soil properties
　4.3. Methodological implications
　4.4. Nutritional implications
5. Conclusions
Acknowledgments
References

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