Impact of biochar on soil microbial activity and its mechanisms

Transcription

1 Impact of biochar on soil microbial activity and its mechanisms Yu Luo 1,2, Mark Durenkamp 1 Qimei Lin 2 and Phil Brookes 1 1 Department of Soil Science, Rothamsted Research, Harpenden, UK 2 China Agricultural University, Beijing, China

2 Soil microbial biomass The collective mass of all soil micro-organisms Has an important role in nutrient cycling

3 Background Biochar could increase impact of biochar on soil microbial biomass and activity increase Impact of biochar on soil microbial biomass and activity mainly depends on the type of char but also on soiltype and experimental conditions 10/18/2010

4 Research questions What is the impact of biochar produced under two different temperatures on soil microbial biomass and activity in different soil? What are the potential mechanisms by which biochar affects microbial biomass and activity?

5 Experimental setup Biochars: produced from Miscanthus sp. at two pyrolysis temperatures at 350 C (BC350) and 700 C (BC700) Biochar rate: 50 g C kg -1 soil Soil: Hoosfield acid strip at ph 4 and 8 Incubation: 90 days at 25 C

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7 Experimental setup Biochars: produced from Miscanthus sp. at two pyrolysis temperatures at 350 C (BC350) and 700 C (BC700) Biochar rate: 50 g C kg -1 soil Soil: Hoosfield acid strip at ph 4 and 8 Incubation: 90 days at 25 C

8 Measurements Microbial biomass C. Microbial activity (CO2). Water extractable biochar C and N FTIR Scanning electro microscopy. 10/18/2010

9 Research questions What is the impact of biochar produced under two different temperatures on soil microbial biomass and activity in different soil?

10 Experimental setup CO 2 evolution, Day 1, 3, 7, 15, 30, 60, 90 Microbial Biomass Day 90

11 Microbial biomass C (µg C g-1 soil) Soil microbial biomass 200 ph ph O O BC350 increase biomass but BC700 doesn t change All data represent the mean of 3 replicates +/- SE

12 µg of CO2-C g-1 soil Soil microbial activity 1200 cumulative 1200 cumulative incubation days incubation days ph 4 ph 4 + biochar 350 ph 4 + biochar 700 ph 8 ph 8 + biochar 350 ph 8 + biochar 700 Cumulative CO 2 evolution was increased by the addition of biochar, especially that produced at 350 C.

13 µg of CO2-C g-1 soil CO 2 evolution production rate 100 ph ph incubation days incubation days ph 4 ph 4 + biochar 350 ph 4 + biochar 700 ph 8 ph 8 + biochar 350 ph 8 + biochar 700 However, most of the increase was observed in the early stages and there were significant differences up to 40 days of incubation.

14 short conclusion Soil microbial biomass and activity is increased by biochar, especially that produced at lower temperature. most of the increase of soil microbial activity was observed in the early stages

15 Further questions Why most of the soil microbial activity increase was observed in the early stages? what is the potential mechanisms by which biochar affects microbial biomass and activity?

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17 10/18/2010

18 Hypothesis: the initial CO 2 flux and the biomass increase is due to the direct microbial utilization of the labile part of biochar as a nutrient source the physical structure of biochar provides a secure environment for microbes, which resulted in the higher microbial biomass

19 Hypothesis: the initial CO 2 flux and the biomass increase is due to the direct microbial utilization of the labile part of biochar as a nutrient source Experiment: biochars were washed 5 times with water, and washing solutions were analyzed to determine nutrient availability to the microbial biomass.

20 Water Extractable Organic Carbon (WEOC) WEOC is more in the BC350 than BC700

21 Water Extractable Inorganic Nitrogen from biochar - Nitrate not detectable

22 FTIR of BC350 and BC cm cm cm cm -1 IR spectra can only provide qualitative, not quantitative information. graphite B 350 C BC 700 C The ratio between absorption intensity at 2940 cm -1 and 1600 cm -1 decreases from 1.18 (350 C) to 0.80 when the biochar is produced at 750 C, indicating a stronger aromatic contribution to the structure of the material.

23 Hypothesis: the physical structure of biochar provides a secure environment for microbes, which resulted in the higher microbial biomass Experiment: Scanning Electron Microscopy (SEM) was used to determine microbial colonization of biochar after 90 days incubation

24 The SEM pictures at Day 0 BC350 BC700

25 BC700 in ph8 soil

26 BC350 in ph8 soil

27 BC700 in ph4 soil

28 BC350 in ph4 soil

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30 Summary Soil microbial activity is increased by biochar, especially that produced at lower temperature. Soil microbial biomass and the initial CO 2 flux is due to the direct microbial utilization of the labile part of biochar as a nutrient source The physical structure of biochar provides a secure environment for microbes, Biochar350 is more likely to provide a better house

31 Acknowledgements Jean Devonshire Wendy Wilmer -Rothamsted Research, Harpenden, UK Guitong Li Xiaorong Zhao -China Agricultural University, Beijing, China CSC funding