Drying-induced changes in phosphorus status of soils with contrasting soil organic matter contents - Implications for laboratory approaches

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• 作者：David L. Achat^a ; ^{dachat@bordeaux.inra.fr} ; Laurent Augusto^b ; Anne Gallet-Budynek^b ; Mark R. Bakker^a
• 关键词：Microbial P ; Water soluble phosphate ions ; Soil drying ; Soil organic matter ; Surface and deep forest soils ; Total organic P
• 刊名：Geoderma
• 出版年：2012
• 期刊代码：28_00167061
• 类别：ear
• 出版时间：October, 2012
• 卷：187-188
• 期：Complete
• 页码：41-48
• 文件大小：763 K

摘要

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 鈥榙ead鈥?organic matter were determined on fresh, moist soils maintained at 4 掳C and on the same soils, oven-dried at 60 掳C. 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%(脳 31 increase) in total inorganic P, and + 11880%(脳 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.