EUROSOIL 2008

Book of Abstracts

Winfried H. Blum, Martin H. Gerzabekand Manfred Vodrazka (Eds.)

University of of Natural Resources and Applied Life Sciences (BOKU)Vienna, Austria, August 2008-08-04

Nilrogen relenlion and ...2008 SP-S8S94

1111111111111111111111 !IIII 11111111111111I1111111111111111111111111 11111111------------- CPAA-21023-1

ISBN: 978-3-902382-05-4

S8594

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potential for SOC storage has to be taken into account whenland use change effects on SOC are assessed.

S01.J.05Impact of tiIIage on carbon and nitrogen storage oftwo Haplic Luvisols

A. Jacobs', R. Raubei, B. Ludwig';1University of Kasse/, Oep. of Environmenta/ Chemistry,Witzenhausen, Germany, 2University Df Gottingen, Institute ofAgronomy, Gottingen, Germany.

The effects of reduced tiIIage systems (minimum tiIIage = MT) onsoil organic carbon (Corg) and N sequestration are notcompletely understood. Thus, the objectives were to investigatethe impact of a MT system (to 5-8cm) on water-stableaggregates and particulate organic matter (POM) and on storageof Corg and N in two loamy Haplic Luvisols in contrast toconventional tiIIage (CT) (to 25cm). Surface soils (0-5cm) andsubsoils (5-20cm) of two experimental fields near G6ttingen,Germany, were investigated. Both sites (Garte-Süd and HohesFeld) received both tiIIage treatments since 37 and 40 years,respectively. In the bulk soil of both fields Corg, N, microbialcarbon (Cmic), and microbial N (Nmic) concentrations wereelevated under MT in both depths. Likewise, water-stablemacroaggregates (>0.25mm) were on average 2.6 times moreabundant under MT than under CT but differences in the subsoilwere generally not significant. For surface soil under MT, aliaggregate size classes <1mm showed about 48% and 56%increased Corg concentrations at Garte-Süd and Hohes Feld,respectively. For greater macroaggregates (1-2, 2-10mm),however, differences were inconsistent but elevations of Ncontents were regular over ali size classes reaching 72% and64%, respectively. In the surface soil, tiIIage system did neitheraffect the yields of free POM and occluded POM nor their Corgand N contents. Moreover, more Corg and N (125-238%) wasassociated under MT within the mineral fractions investigated.To sum up, similar to no-tillage, a long-term MT treatment of soilenhanced the stability of macroaggregates and thus was able tophysically protect and to store more organic matter (OM) in thesurface soil in contrast to CT. The increased storage of Corg andN did not occur as POM but as mineral-associated OM.

S01.J.06Nitrogen retention and plant uptake on a highlyweathered central Amazonian Ferralsol amendedwith compost and charcoal

C. steiner', B. Glasei, W. G. Teixeire", J. Letimenn', W. E. H.Bium", W. Zecb";1Biorefining and Carbon Cycling Program, University of Georgia,Athens, GA, United States, 20epartment of Soi! Physics,University of Bayreuth, Bayreuth, Germany, JEmbrapa AmazoniaOcidental, Manaus, Brazi/, "Depenment of Crop and Soi!Sciences, Cornell University, Ithaca, NY, United States, slnstituteof Soi! Research, University of Natural Resources and App/iedLife Sciences, Vienna, Austria, "tnstitute ot Soi! Science and Soi!Geography, University of Bayreuth, Bayreuth, Germany.

Inspired by the sustained fertility of anthropogenic Terra Pretasoils in the central Amazon Basin, we studied the effect ofcharcoal as soil amendment. The use of charcoal as recalcitrantsoil amendment can have important implications for sustainableland use in the humid tropics and the earth's carbon budget.Leaching losses of nitrogen (N) are a major limitation of cropproduction on strongly weathered soils and under heavyrainfalls, as in the humid tropics. We established a field trial inthe central Amazon Basin (near Manaus, Brazil), in order tostudy the influence of charcoal and compost on the retention ofN. Fifteen months after organic matter admixing (O - 0.1 m soildepth), we added 15N labelled ammonium sulphate (27.5 kg Nha' (NH.hSO. at 10 atom% excess). The tracer was measuredin the top soil (O - 0.1 m) and plant samples were taken at two

successive sorghum (Sorghum bicaor L. Moench) harvests. TheN recovery in biomass was significantly higher when the soilcontained compost (14.7 % of applied N) in comparison to onlymineral fertilized plots (5.7 %), due to a significantly higher cropproduction during the first growth period. After the secondharvest, the N-retention in the soil was significantly higher in thecharcoal amended plots (15.6 %) in comparison to only mineralfertilized plots (9.7 %). The total N recovery in soil, crop residuesand grains was significantly (P < 0.05) higher in compost(16.5%), charcoal (18.1%) and charcoal plus composttreatments (17.4%), in comparison to only mineral fertilized plots(10.9%). Organic amendments increased the retention of appliedfertilizer N. One process within this retention was found to be therecycling of N taken up by the crop.

S01.K.01Soil structure dynamics and carbon sequestration

U. Franko, K. Kuka;UFZ, Halle, Germany.

Soil structure has a strong impact on SOM turnover. Therecently developed CIPS model demonstrates this verysuccessful. The partition of the total pore space into micro,rneso- and macropores and the subsequent distribution ofspecific microbial activity to these classes proofed to be veryuseful to understand long term dynamics without sophisticassumptions like an inert pool. The CIPS model has recenttybeen integrated in the CANDY model in order to perform morecomplex scenario simulations.It is well known that SOM has an impact on soil structure. A newsubmodel in CANDY has been developed in order to simulatethese effects also. In this context we consider as structuralindicators field capacity (FCAP), permanent wilting point (PWP)and total pore volume (PV) because these are used to controlthe soil water dynamics in the CANDY model and also asproxies to identify the pore space classes in CIPS. The maindriver of soil structure changes is PV depending on the ratio ofbulk density to particle density which are both dependent onSOM. FCAP and PWP can be calculated using a pedotranslerfunction if PV is known. Particle density is calculated using theapproach of RÜHLMANN ET AL. (2006) depending on SOMcontento Bulk density is modelled following the concepts 01SCHAAF(1998) (tillage and recompaction) andRÜCKNAGEL(2007) (compaction from machinery). The resultingmodel handles soil structure no longer as a constant para meterbut a soil state variable depending on management, clirnata andSOM.The integrated CANDY&CIPS model simulates not only thedynamics of SOM pools but also their ages that are varyingbetween 10 to 3000 years if SOM is in steady state.

S01.K.02Micro-scale modelling of carbon turnover driven bymicrobial succession at a biogeochemical interface

J. Ingwersen, C. Poli, T. Streck, E. Kandeler;/nstitute of Soi! Science and Land Evaluation, Stuttgart,Germany.

The detritusphere is a very thin but microbiological highly activezone in soil. To trace the fate of litter carbon in the detrituspherewe developed a new 1D dynamic mechanistic model. In amicrocosm experiment soil cores were incubated with 13Clabelled rye residues (Õ'3C=299%o), which were placed on thesurface. Microcosms were sampled after 3, 7, 14,28,56 and 84days and soil cores were separated into layers of increasingdistance to the litter. Gradients in soil organic carbon, dissolvedorganic carbon, microbial biomass and activity were detectedover a distance of 3 mm from the litter layer. The newlydeveloped 1D model simulates both the total carbon and the 13Ccarbon pools and fluxes, so that it was possible to include the13Cdata in model optimisation. The special feature of the model

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