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Basal organic phosphorus mineralization in soils under different farming systems

Oehl, F.; Frossard, E.; Fliessbach, A.; Dubois, D. and Oberson, A. (2004) Basal organic phosphorus mineralization in soils under different farming systems. Soil Biology & Biochemistry (36), pp. 667-675.

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Soil organic P (Po) mineralization plays an important role in soil P cycling. Quantitative information on the release of available inorganic P (Pi) by this process is difficult to obtain because any mineralized Pi gets rapidly sorbed. We applied a new approach to quantify basal soil Po mineralization, based on 33PO4 isotopic dilution during 10 days of incubation, in soils differing in microbiological activity. The soils originated from a 20 years old field experiment, including a conventional system receiving exclusively mineral fertilizers (MIN), a bioorganic (ORG) and bio-dynamic (DYN) system. Indicators of soil microbiological activity, such as size and activity of the soil microbial biomass and phosphatase activity, were highest in DYN and lowest in MIN. In order to assess Po hydrolysis driven by phosphatase in sterile soils, a set of soil samples was g-irradiated. Basal Po mineralization rates in non-irradiated samples were between 1.4 and 2.5 mg P kg21 day21 and decreased in the order DYN . ORG $ MIN. This is an amount lower, approximately equivalent to, or higher than water soluble Pi of MIN, ORG and DYN soils, respectively, but in every soil was less than 10% of the amount of P isotopically exchangeable during one day. This shows that physico-chemical processes are more important than basal mineralization in releasing plant available Pi. Organic P mineralization rates were higher, and differences between soils were more pronounced in g-irradiated than in nonirradiated soils, with mineralization rates ranging from 2.2 to 4.6 mg P kg21 day21. These rates of hydrolysis, however, cannot be compared to those in non-sterile soils as they are affected by the release of cellular compounds, e.g. easily mineralizable Po, derived from microbial cells killed by g-irradiation. q 2004 Elsevier Ltd. All rights reserved.

EPrint Type:Journal paper
Keywords:P mineralization, Isotopic dilution, Phosphatase activity, P availability, Farming systems, Anbautechnik Einjährige Kulturen, Bodenfruchtbarkeit
Subjects: Soil > Nutrient turnover
Soil > Soil quality > Soil biology
Soil > Soil quality
Research affiliation: Switzerland > ETHZ - Agrarwissenschaften
Switzerland > Agroscope > ART - Reckenholz location
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Related Links:http://www.fibl.org/forschung/anbautechnik-einjaehrig/index.php, http://www.elsevier.com/wps/find/journaldescription.cws_home/503298/description#description
Deposited By: Fliessbach, Dr. Andreas
ID Code:2791
Deposited On:08 Jun 2004
Last Modified:12 Apr 2010 07:29
Document Language:English
Refereed:Peer-reviewed and accepted

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