Post on 20-Mar-2020
Effects of biochar on soil chemical and biological properties in high and
low pH soils.Phil Brookes, Luo Yu, Mark Durenkamp and
Qimei Lin
Rothamsted Research, UK
China Agricultural University, Beijing, China
The Hoosfield Acid strip at Rothamsted
• More than 100 years old.
• Sown with wheat every year.
• pH range about 8.3 to 3.8.
• Never received fertilizer.
Site: Hoosfield acid strip
pH 8.0
pH 5.0
pH 4.0
flinty silty clay loam (18-27 % clay)
HOOSFIELD ACID STRIPStarted more than 100years ago
3.5
4.5
5.5
6.5
7.5
8.5
0 20 40 60 80 100 120 140 160 180 200
Distance (m)
Soil pH
Wheat crop along Hoosfield acid strip
pH 8.0 pH 6.7 pH 5.0 pH 4.5
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
0 20 40 60 80 100 120 140 160 180 200
Distance (m)
Org
an
ic C
(%
)Hoosfield acid strip
g
bio
ma
ss C
g-1
so
il
0
50
100
150
200
250y = 188 - 3496(-0.8x)
R2 = 0.80
p < 0.0001
Soil pH
3 4 5 6 7 8 9
g
nin
hyd
rin
-N g
-1 s
oil
0
1
2
3
4
5y = -18 + 9.8 x - 1.6 x
2 + 0.1 x
3
R2 = 0.90
p < 0.0001
Biomass C and ninhydrin-N v soil pH
Experimental Hypothesis
• Incorporation of biochar could improve soil properties and overcome the adverse effects of soil pH.
Experimental design
• Soil: Hoosfield pH 4 and pH 8
• Biochar: Miscanthus produced at 350 and 700 oC,added at 5 % C by weight.
• Incubation: 90 and 180 days at 40 % Water Holding Capacity.
• Substrate: with and without ryegrass at 5000 µg C g-1
Treatments
• O Nil
• S Substrate (5000 ug ryegrass C/g soil)
• BC350 Biochar made at 350 °C
• BC700 Biochar made at 700 °C
• BC350 + S Biochar made at 350 °C + substrate
• BC700 + S Biochar made at 700 °C + substrate
Measurements
• Water-extractable elements.
• K2SO4-extractable Mn, Al (Mg and Ca).
• Extractable ammonium and nitrate.
• Microbial biomass C.
• Adenosine 5 triphosphate (ATP).
• Total C and N and CO2-C
Water extractable elements in biochar.
0
40
80
120
160
Ca K Mg Mn Na P S Cl
µg g-1 biochar
BC350
BC700
K2SO4 extractable Al at 90 daysat pH 4
0
100
200
300
400
500
600
O S 350 700 350+S 700+S
µg g-1 soil
K2SO4 -extractable Mn at 90 daysat pH 4
020406080
100120140
O S 350 700 350+S 700+S
µg g-1 soil Mn
Soil pH at 90 and 180 days
6
7
8
9
pH 8 pH 8 + substrate
pH 8 + BC350
pH 8 + BC700
pH 8 + substrate+
BC 350
pH 8 + substrate+
BC 700
pH
treatments
pH 8 soil
Day 0 Day 90 Day 180
Soil pH at 90 and 180 days
3.66
3
4
5
6
pH 4 pH 4 + substrate
pH 4 + BC350
pH 4 + BC700
pH 4 + substrate+
BC 350
pH 4 + substrate+
BC 700
Ph
treatments
pH 4 soil
Day 0 Day 90 Day 180
Al and Mn at 180 days incubationat pH 4
• Practically identical results with Al and Mn at 180 d incubation at pH 4.
• Al and Mn practically undetectable at pH 8 in all treatments
Extractable Al and Mn at 90 and 180 days incubation at pH 4
• Al decreased by 50 % or more with biochar at 350 and 700 °C, with or without substrate, at pH 4.
• Mn decreased by 90 % with biochar at 700 °C, with and without substrate, at pH 4. No effect with biochar at 350 °C.
• We do not fully understand the mechanisms involved. Probably linked to soil pH changes.
Al and Mn not detectable at pH 8.
Effects of pH on soil CO2 evolution
Effects of soil pH 4 on CO2 evolution
0
500
1000
1500
2000
2500
3000
0 50 100 150 200
µg
CO
2-C
g-1
soil
incubation days
cumulative
pH 4 pH 4 + substrate
pH 4 + biochar 350 pH 4 + biochar 700
pH 4 + substrate + biochar 350 pH 4 + substrate + biochar 700
Effects of soil pH 8 on CO2 evolution
0
500
1000
1500
2000
2500
3000
3500
4000
0 50 100 150 200
µg
CO
2-C
g-1
soil
incubation days
cumulative
pH 8 pH 8 + substrate pH 8 + biochar 350
pH 8 + biochar 700 pH 8 + substrate + biochar 700 pH 8 + substrate + biochar 350
• Effects of biochar on biomass C
Changes in biomass C at pH4
0
50
100
150
200
250
300
O S 350 700 350+S 700+S
Microbial biomass C (µg C g-1 soil) Changes in biomass C
pH 4
Changes in biomass C at pH 8
0
50
100
150
200
250
300
O S 350 700 350+S 700+S
Microbial biomass C (µg C g-1 soil) Changes in biomass C
pH 8
Microbial ATP and biochar
Mean biomass ATP concentration10.6 µmol ATP g-1 biomass C
Jenkinson, Davidson & Powlson (1978)
ATP concentration of microbial biomass
10.4 moles ATP g-1 biomass C (n=207)
Contin et al. (2001)
Acidic reagents only
ATP and biomass C relationships in soils at pH 4 and 8 with and without biochar
y = 0.0113xR² = 0.7594
y = 0.0135xR² = 0.9875
00.5
11.5
22.5
33.5
4
0 100 200 300
ATP µmol g-1 soil
Biomass C (µg g-1 soil)
Biomass ATP relationships at Day 180
with Biochar
without Biochar
Biomass ATP concentrations
• Jenkinson et al. (1978) 10.6 umol ATP g-1
biomass C
• Contin et al. (2001) 11.7 umol ATP g-1 biomass C
• Luo Yu (2010) 12.4 umol ATP g-1 biomass C
Efficiency of biosynthesis - Eb
• % of added substrate C incorporated into biomass:
Eb = [100 (biomass C in soil +substrate)
minus
(biomass C in soil)]
_______________
(C in substrate)
Efficiency of biosynthesis at 90 days of incubation
Treatment Soil pH 4 Soil pH 8
Control + ryegrass 1.42% 4.86 %
BC350 + ryegrass 2.22 % 2.96 %
BC700 = ryegrass______________________5000 ug C g-1 soil5% C by weight
0.76 %______________________
3.48 %______________________
Efficiency of biosynthesis
• Higher efficiency of biosynthesis at pH 8 than pH 4. There is a ‘metabolic cost’ for organisms living in difficult environments.
• No evidence of increased efficiency of biosynthesis with biochar at high or low pH.
Efficiency of biosynthesis
• Higher efficiency of biosynthesis at pH 8 than pH 4. There is a ‘metabolic cost’ for organisms living in difficult environments.
• No evidence of increased efficiency of biosynthesis with biochar at high or low pH.
Conclusions
• Significant increase in pH with biochar added at 350 and 700 °C. Greater with 700 °C.
• No change in biosynthesis efficiency with biochar but greater efficiency at pH 8.
• Increases in biomass C following substrate addition and with biochar at 350 °C. No change (or even small decrease)with biochar at 700 °C.
• Biochar did not change ATP concentration in microbial biomass.
Acknowledgements
• Rothamsted Research is funded by the Biotechnological and Biological Sciences Research Institute (BBSRC).
• We thank Rhys Ashton for help with the experiments.
Site: Hoosfield acid strip
Site: Hoosfield acid strip
Site: Hoosfield acid strip