The effect of biochar soil-carbon stabilization in a highly SOM-depleted soil

Transcription

1 The effect of biochar soil-carbon stabilization in a highly SOM-depleted soil Claudia MBF Maia & Saran P Sohi Embrapa Forestry, BR, Brazil; Rothamsted Research, UK University of Edinburgh, UK claudia.maia@cnpf.embrapa.br

2 INTRODUCTION Biochar => an important strategy to store stable C in soils but: What is its impact on the dynamics of other soil carbon? How is biochar modified by biological interaction with plant roots in soil?

3 Hypothesis and Aim Hypothesis: The presence of biochar in soil will accelerate the accumulation of plant-derived organic matter Aim: To follow the inputs and dynamics of organic C added into an amended soil profile by maize Approach: 13C/12C isotopic ratio monitored monthly during a cropping cycle

4 13C/12C isotopic ratio δ 13 C (in ): ( 13 C/ 12 C)sample ( 13 C/ 12 C)standard x ( 13 C/ 12 C)standard PDB standard ( Belemnite (carbonate from a fossil marine shell, Pee Dee C3 from -22 to -30 C4 from -10 to -14

5 13C/12C isotopic ratio Maize* Eucalyptus** Eucalyptus charcoal ( 2004 *( Kristiansen et al ( 2010 **(Mendonça et al

6 Materials and preparation methods ( pyrolysis Biochar: eucalyptus charcoal fines (slow ( dunnii (from Brazil, Eucalyptus Initial basic properties: moisture, ash content, volatile and fixed carbon Homogenization: crushing, sieving and leaching

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8 Biochar analysis Moisture (%) Ash (%) Calorific Value Volatile s Fixed Carbon (%) 37,34 29,46 16,61 28,39 42,14

9 crushing leaching grading

10 Table 2. Size distribution of the biochar after grinding and washing: Biochar analysis Predominant size > 2.5 <4.0 mm diameter Fragments < 53 m total 0.48 %. Sieve Mass SD mm g >6.7 3,39 0,62 > 5.6 9,33 2,81 > ,03 1,48 >2.5 16,63 1,64 > ,77 1,73 > ,56 2,69 >0.5 14,29 0,44 > ,72 1,38 > ,80 0,81

11 ( Research Woburn farm (Rothamsted

12 Woburn biochar experiment site and layout Soil mine is area kept bare for 62 yr ( 0.5 very depleted in soil organic mater ( av 0.9 sd sensitive background for crop-induced effects Four treatments (all +lime, +fertilizer): Maize planted, biochar amended soil Unplanted, biochar amended soil Maize-planted soil Unplanted soil Plots 3.5 m x 6 m ( reps Randomized block design (5

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14 Woburn biochar experiment implementation ( recommended Liming and fertilizer applied (as ( mass Biochar rate 30 t ha -1 (dry a doubling of soil carbon ( -1 ha equivalent of 20.5 tc ha -1 (and 153 KgN Incorporated to 15 cm deep Sampling monthly from 0 25 cm and cm ( 2009 (April to October

15 Liming Biochar application

16 Incorporation and planting

17 Soil sampling: nine subsamples per plot ( reference ) 28/04/ /05/ /06/ /07/ /08/ /10/2009 ( 08/09/2009 (maize harvest

18 Woburn biochar experiment soil fractionation Fractionation of soil organic carbon pools ( 2001 al., (development of Sohi et

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20 Results: biomass production No biochar planted: 28.8 t ha -1 + biochar treatment: 33.7 t ha -1 ( nutrients (+17%, even without readily leachable

21 Results: isotopic ratio ( cm At harvest δ 13 C top soil (0 to 25 ( (-27.5 soil Unplanted non-amended ( (-26.6 soil Highest δ 13 C in planted, non-amended ( (-28.0 soil Unplanted, biochar amended ( (-28.4 C Planted, biochar-amended δ 13 biochar-amended soil has more as well as low carbon than unamended

22 Results Dynamics of isotopic ratio variation (δ C 13 ) in soil at 0 to 25 cm depth during the first maize cycle (2009).

23 Results: isotopic ratio %C d elta13c % 0-25cm 0,38-26,20-1,45 1,26 Soil -28,55 SOM -4,43 from SOM 1,16 from - 28,73-4,04 0,50-27,31-1, cm Carbon 0,31 (tc -27,07 maize (%) (by -1,16 maize 0,45-27,73-1,63 0,44-27,52-1,59 0,46-27,44 ha-1) -1,68 d 13 C) (t ha -1 ) No biochar (planted) -26,20 13,3 7,98 1,06 30 t ha -1 biochar (charcoal) -28,55 44,1 1,17 0,52 No biochar or crop -26,20 17, t ha -1 biochar (charcoal) -28,55 40,6 - -

24 Results: isotopic ratio Subsoil (25 to 50 cm): Differences between δ 13 C smaller ( plots but less biochar carbon in amended ( ) Highest δ 13 C in planted un-amended soil ( ) Lowest δ 13 C in biochar-amended fallow plots Plots un-amended unplanted δ 13 C is

25 Results: isotopic ratio of organic fractions -25,00 delta 13C -25,00 delta 13C -25,50-25,50-26,00-26,00-26,50-26,50-27,00-27,00-27,50-27,50-28,00 None Maize Biochar Maize -28,50 Biochar Fallow 1 None Fallow 5 Free light fraction -28,00-28,50 None Maize Biochar Maize Biochar Fallow 1 None Fallow 5 Intraggregated fraction Isotopic variation in organic fraction by treatment at the 1st and at the 5th soil sampling

26 Conclusion The isotopic signature of biochar is distinct in soils and organic fractions not amended with biochar. Although total SOC difference between amended and unamended is 30,8 t/ha (equivalent to the biochar input ), estimated SOC % from maize in the amended treatments is half of unamended. This difference can indicate higher 13 C losses by root or microbial respiration, for example, on amended plots. 30, 24 t of biochar in a sandy soil: increases 2,7 times the total C content and 17% biomass production of maize.

27 Acknowledgements This study was supported by Rothamsted Research UK* The fellowship of Dr Maia was funded by Embrapa and the Ministry of Agriculture of Brazil *Keith Goulding, Steven Goward, And Hunt, Andy MacDonald, Paul Poulton, Mark Durekamp

28 Thank you for your attention

29 Thank you for your attention!