Investigation of biochar effects as a non-structural BMP on soil erosional responses using a rainfall simulator Ataallah Khademalrasoul1, Nikolaus.J. Kuhn2, Yaxian Hu2, Bo V. Iversen1, Goswin Heckrath1 1- Department of Agroecology, Faculty of Science and Technology, Aarhus University, Blichers Allé, Postbox 50, DK 8830 Tjele, Denmark. 2- Physical Geography and Environmental change, Department of Environmental Sciences, University of Basel, Klingelbergstrasse 27, CH - 4056 Basel, Switzerland Ataalah.khademalrasoul@agrsci.dk,PhD student Introduction Table 2. The average of runoff and infiltration of control and biochar-amended soils A B Recent studies have shown the potential of biochar as a non-structural best management practice (BMP) for improving soil aggregation thereby reducing the erosion risk. Rainfall simulation provides the possibility to efficiently quantify the effects of different management scenarios on erosion and runoff potential under controlled conditions. Plot ID RC Total runoff Total sediment (gr) Eroded SOC Total infiltration (mm) Control 0.29 ± 0.02 67.6 ± 4.4 170 ± 15 182 ± 19 73 ± 3 Biochar 0.23 ± 0.01 50.1 ± 2.7 101 ± 12 85 ± 10 80 ± 4 RC: Runoff coefficent OC: Organic carbon Objectives Fig 1. (A) Rainfall-runoff simulator and (B) Rainfall intensity measurement (1) to compare runoff and sediment generation between a biochar and an unamended control treatment on an arable sandy loam soil (2) to determine the effect of the biochar treatment on soil organic carbon (SOC) erodibility Table 1. Soil properties of studied plots plots Treatment Clay Silt Sand SOC TIC Stable aggregates pH   - % -  1 Control 8.8 12.2 79.0 1.15 0.64 22.0 8.50 2 Biochar 8.5 12.6 78.9 1.44 0.57 69.0 8.75 3 9.3 12.3 78.4 1.16 0.24 39.1 8.45 4 9.5 14.0 76.5 1.55 0.07 74.5 8.30 5 8.7 13.0 78.3 0.04 27.2 7.77 6 10.0 13.5 1.52 0.03 72.1 7 76.7 1.19 23.3 7.50 8 11.0 12.0 77.0 77.1 7.32 A B Materials and Methods Fig. 4. The soil surface patterns of (A) biochar-amended soils and (B) unamended control soils Study site Risø, Denmark 8 plots (6m * 8m) four control and four biochar-amended plots (from Birchwood) (2012, 2 kg m-2) The studied plots cropped in rotation of peas, wheat, barley and oilseed No organic manuring for >25 years Soil samples from 0-0.20 m ploughed layer Measured parameters Aggregate stability SOC in the sediment and crust Total inorganic carbon (TIC) Rainfall-runoff simulation setup (Fig. 1) Nozzle 2 m above the soil surface Rainfall intensity of 30 mm h-1 3.5 hour rainfall event Round flume with an outside diameter of 50 cm and a center opening of 10 cm, 10 % steepness. Collection of runoff and sediment in order to measure erosional responses (runoff, erosion rates, etc.) Biochar application improved soil infiltrability and aggregate stability (Table 1 and 2). The biochar-amended soils compared to unamended soils, showed substantially lower soil erosion and runoff rates (Fig. 2A and B). Enrichment ratio of SOC of biochar-amended soils was lower than the unamended control soils due to depletion of SOC during the rainfall event and due to the decline in the selectivity of soil particle erosion over time (Fig. 3). Total amount of eroded SOC from biochar-amended soils was lower than unamended control soils. The visual assessment of soil surface alterations indicated the differences in soil surface development and crust formation due to armouring effects of biochar particles (Fig. 4A and B). Results Fig. 2. (A) Runoff and (B) erosion rates during the 3.5 hour rainfall simulation Conclusions Biochar application already in a short term leads to an improvement of soil aggregation, increased the soil infiltration leading to a lowering of soil erosion and runoff potential. Acknowledgements The technical assistance of Stig T. Rasmussen for soil sampling and Ruth Strunk in Basel University with the laboratory analyses is gratefully acknowledged. Also help of Henrik Hauggaard-Nielsen in Risø site is gratefully acknowledged. Fig. 3. Enrichment ratio of SOC (sediment to original soil) during rainfall simulation test