Eichler-Löbermann, Bettina

Uptmoor, Ralf

Wacker, Katrin

Zicker, Theresa

English

JKI Open Journal Systems (Julius Kühn-Institut)

25th International Symposium of the International Scientific Centre of Fertilizers Significance of Sulfur in High-Input Cropping Systems Groningen (The Netherlands), September 5-8, 2017     15 Phosphorus budgets and bioavailable phosphorus content in soil - results of a long-term field experiment  Bettina Eichler-Löbermann, Theresa Zicker, Katrin Wacker and Ralf Uptmoor University of Rostock, Chair of Agronomy and Crop Science, J. von Liebig Weg 6, 19059 Rostock, Germany (E-mail: bettina.eichler@uni-rostock.de)  Due to the scarcity of mineable phosphorus (P) an efficient use of P is a main objective in sustainable agriculture. An application of P adapted to crop requirements and the nutrient recycling with wastes and residues can help to achieve this aim. The content of bioavailable P in soil can be used to evaluate the current soil P status and to calculate the fertilizer need. However, the availability of P in soil depends not only on the P input but is also regulated by biological and biochemical processes in soil and environmental conditions. Long-term field experiments can give an extensive overview about the effectiveness of P application also considering the influence of annual environmental conditions, P mobilization and translocation processes in soil. At the Rostock long-term field experiment the effect of single and combined P treatments are investigated since 1998.   The long-term field experiment is located in the northeast of Germany and influenced by a maritime climate (600 mm annual rainfall; 8.1°C annual temperature). The initial double-lactate soluble P content (Pdl) of the soil was 42.2 mg kg-1 indicating a sub-optimal P supply according to the German soil P test classification. The trial was designed as a randomized split plot experiment in four replicates. The main plots comprised three organic P treatments (no P, biowaste compost, and cattle manure). The subplots comprised three inorganic P treatments (no P, Triple-super-P (TSP), and biomass ash). Compost and manure were applied at rates of about 30 t ha-1 in September every three years beginning in 1998. TSP and biomass ash were applied annually at rates of 21.8 to 30.0 kg P ha-1. Soil and plant sampling was done twice a year and a broad spectrum of soil characteristics, crop yields and crop P uptakes were investigated.   The different P treatments and their combinations resulted in different crop P uptakes and P budgets (Table 1). These management effects also influenced the bioavailable P contents in soil (measured as Pdl; Table 2). Highest contents of Pdl were measured in the combined fertilizer treatments with compost and inorganic fertilizers (about 55 mg kg-1 soil). Compost application resulted in higher Pdl contents than manure application, which could be explained by the relatively high percentage of mineralized P in compost and its stable organic compounds. The organic fertilizers had a comparable P fertilizer effect as the inorganic fertilizers. Close significant (p<0.05) correlations between the P budgets and the Pdl concentrations in soil in the particular periods were calculated ranging from 0.73 to 0.98. However, the data also showed fluctuations of the Pdl values during the experimental period, which cannot be explained only by the P supply. Here, we expect a decisive role of biological and chemical P turnover processes which may be affected by weather conditions. It can be concluded that P budgets can be used to predict changes in 25th International Symposium of the International Scientific Centre of Fertilizers Significance of Sulfur in High-Input Cropping Systems Groningen (The Netherlands), September 5-8, 2017     16 soil test P over long periods under field conditions but may be unsuitable to reflect the current soil P status.   Acknowledgements: The study was supported by the BonaRes project InnoSoilPhos (No. 031A558, German Federal Ministry of Education and Research).     Table 1. Total P supply, total crop P uptake (P removal) and total P budget accumulated after 17 years in field experiment Rostock  Treatment  Total P supply  P removal (kg ha-1) P budget  Control 0 422   -422 TSP 379 467     -88 Ash 348 439     -91 Manure 391 465     -74 Man + TSP 770 467    303 Man + Ash 739 482    257 Compost 396 470     -74 Com + TSP 775 498    277 Com + Ash 744 508    236 TSP = Triple-Superphosphate, Manure/Man = Cattle manure,  Compost/Com = Biowaste compost, Ash = Biomass ash   Table 2. Contents of bioavailable P (Pdl, mg kg-1 soil) as average of three-year periods and over the whole experimental time from 1998 to 2015 in the Rostock field experiment Treatment 1998-2000 2001-2003 2004-2006 2007-2009 2010-2012 2013-2015 Mean Control 35.7a 41.1a 36.6a 32.3a 30.4a 28.8a 34.a TSP 41.7bc 51.4cd 48.1c 40.1b 38.8b 36.7b 43.8c Ash 36.1a 46.7b 44.6b 41.4b 37.0b 36.8b 41.b Manure 40.7b 50.0c 48.9cd 40.5b 37.1b 37.4b 43.5c Man + TSP 42.2bc 58.7e 54.2f 47.2c 44.6d 44.6d 49.e Man + Ash 46.8de 51.8cd 51.8ef 44.8c 41.7c 43.3cd 47.d Compost 44.3cd 53.1d 51.1de 46.8c 45.2d 41.2c 47.d Com + TSP 48.0e 58.8e 61.1g 54.9d 53.2e 49.5e 55.3f Com + Ash 51.2f 59.3e 60.3g 54.6d 51.3e 49.2e 55.2f Mean 43.0 52.3 50.8 44.7 42.1 40.8  Different letters indicate significant different means between fertilizer treatments, Duncan-test P ≤ 0.05; TSP = Triple-Superphosphate, Manure/Man = Cattle manure, Compost/Com = Biowaste compost, Ash = Biomass ash, each period consists of three single years, soil sampling was done every single year    

Phosphorus budgets and bioavailable phosphorus content in soil - results of a long-term field experiment

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Phosphorus budgets and bioavailable phosphorus content in soil - results of a long-term field experiment

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