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Phosphorus budget and phosphorus availability in soils under organic and conventional farming

Oehl, F.; Oberson, A.; Tagmann, H.U.; Besson, J.M.; Dubois, D.; Mäder, P.; Roth, H.-R. and Frossard, E. (2002) Phosphorus budget and phosphorus availability in soils under organic and conventional farming. Nutrient Cycling in Agroecosystems, 62, pp. 25-35.

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Summary

The aim of this work was to assess to which extent organic farming practices would affect the accumulation of total and available phosphorus (P) in a cropped soil in comparison to conventional practices. In order to achieve this, soil samples were taken from a long-term field trial comparing a non-fertilised control (NON), two conventionally cultivated treatments (MIN, CON), and two organically cultivated treatments (ORG, DYN). Soil samples were taken from each treatment at two depths (0-20 and 30-50 cm) before starting the field trial (1977) and at the end of every three crop rotations (1984, 1991 and 1998). They were then analysed for total P (Pt ), total inorganic P (Pi ), total organic P (Po) and isotopically exchangeable Pi . After 21 years, the average P input-output budget reached -20.9 kg P ha−1 a−1 for NON, -7.8 for DYN, -5.7 for ORG, -5.0 for MIN and +3.8 for CON. Total P, Pi as well as the amount of Pi isotopically exchangeable within 1 minute (E1) were positively correlated to the P budget. Comparison between P budget and Pt in the top- and subsoils of the fertilised treatments suggested a net transfer of P from the 0–20 to the 30–50 cm layers between 13 and 26 kg P ha−1 a−1during the first rotation and between 3 and 12 kg P ha−1 a−1during the second rotation. During the third rotation a net upward movement of P from the subsurface to the topsoil ranging between 3.7 and 10.5 kg P ha−1 a−1was estimated. In the topsoil, E1decreased from an initial value of 12 mg P kg−1 to 11 in CON, 8 in MIN, 6 in ORG, 5 in DYN and 2 in NON after 21 years. In the subsoil, E1 increased from an initial value of 2 mg P kg−1 to 4 in MIN, ORG, DYN and NON and to 6 in CON. These results show that, with the exception of NON, all treatments had still an adequate level of available P after 21 years of trial and that, in this low to moderately P sorbing soil, an equilibrated input-output budget allows to maintain P availability at a constant level. In the organic systems, yields have so far partly been attained at the expense of soil reserves or residual P from earlier fertiliser applications.


EPrint Type:Journal paper
Keywords:conventional farming, integrated production, organic farming, P availability, P budget, P loss, P movement, Department of Soil Sciences, Long-term Experiments, DOK-Trial, Systems comparison
Agrovoc keywords:
LanguageValueURI
Englishconventional farmingUNSPECIFIED
Englishintegrated productionUNSPECIFIED
Englishorganic farmingUNSPECIFIED
EnglishP availabilityUNSPECIFIED
EnglishP budgetUNSPECIFIED
EnglishP lossUNSPECIFIED
EnglishP movementUNSPECIFIED
Subjects: Soil
Research affiliation: Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Switzerland > ETHZ - Agrarwissenschaften
Switzerland > Other organizations
Deposited By: Mäder, Paul
ID Code:26761
Deposited On:26 Sep 2014 11:36
Last Modified:26 Sep 2014 11:36
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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