practical benefits of biochar amendment to agricultural systems: linking soil and microbial...
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Zi vs Pi Node Discrimina/on Phyla Distribu/on Among Network Nodes
Biomass pyrolysis products (biochar) have the poten7al to address both climate change and the degrada7on of agricultural soils. As a soil amendment biochar can provide long-‐term C sequestra7on, improve soil quality, water reten7on, crop produc7vity and food produc7on sustainability. The prac/cal value of biochar as a soil amendment hinges on whether it produces significant and persistent improvements in crop yields and soil quality and can be incorporated into an economically-‐viable, sustainable agronomic system.
Background Molecular Ecological Networks
Prac/cal Benefits of Biochar Amendment to Agricultural Systems: Linking Microbial Processes to Economic Feasibility and Sustainability
Susan Crow 1, Jonathan Deenik 1, C. Ryan Penton 2, John Yanagida 1 (1 Univ. of Hawaii at Manoa, HI; 2 Arizona State Univ., College of LeRers and Sciences)
Acknowledgements: Susan Migita and Poamoho Research Sta7on, Roger Corrales, Waimanalo Research Sta7on, and Diacarbon.
Impact Our long-‐term goal is to improve resource management through more sustainable agricultural prac7ces by addressing the process-‐level origins of improvements in our produc7on systems. Greenhouse gas reduc/on and carbon sequestra/on through biochar amendment, both direct through the incorpora7on of recalcitrant organic maRer and indirect through reduc7on in net GHG flux through impacts on soil biological, chemical, and physical processes, are cri7cal to produc7on systems that strive for environmental sustainability. By focusing in part on the underlying processes driving GHG flux and carbon sequestra7on, the results can be more broadly applied to other agricultural regions.
Experimental Outline
Microbial Analyses . 16S I l lumina sequencing for bacterial community composi7on, 36 samples per treatment/7me, processed through QIIME with chimera detec7on, clustered at 3% dissimilarity. RMT analysis using Zhou Lab Molecular Ecological Analysis pipeline and visualized in Cytoscape, sta7s7cs using PRIMER-‐E.
Field Trials. Sweet corn and Napier (bioenergy grass) are cropped at two sites (Waimanolo-‐mollisol and Poamoho-‐oxisol) in a replicated, randomized block design. Fer7lized with fish bone meal, lime applied to the oxisol. Biochar and no biochar treatments. Corn is harvested ~72 days aeer plan7ng, Napier every 6 months. Biochar is applied at 1% rate on 15x20 e plots, fish bone meal applied at 24 lbs/plot.
Current Conclusions
USDA-‐Annual Project Director’s Mee/ng 2015 USDA-‐NIFA award number 2012-‐67020-‐30234
Current and Future Work Microbial Analyses 1. Fungal ITS sequencing-‐ Subset of field samples 2. qPCR-‐ NosZ and 16S rRNA genes to correlate with N flux data 3. SIP-‐enabled metagenomics -‐ 13C labeled Napier 4. Aggregate-‐size-‐ Geochip for C func7onal genes 5. Buried biochar bags-‐ Bacterial and fungal communi7es 6. Bacterial abundance-‐ temperature sensi7vity incuba7ons Temperature Sensi/vity 1. Expanded temperature range 19-‐43 °C for threshold effect Carbon 1. C incorpora7on into aggregate size frac7ons 2. Priming effects on long-‐term temp. sensi7vity incuba7ons Plant-‐Microbial Interac/ons 1. Greenhouse corn – Analysis of plant hormone produc7on,
possibly PGPR Economic Analyses 1. C value through GHG losses and C sequestra7on 2. Es7mates of payback period also using es7mates of local biochar
produc7on
RMT-‐based Molecular Ecological Network Analysis 1.) Biochar amendment resulted in higher modularity, more nodes and links. Representa7ve of a “larger world” with more interac7ons that link at a higher efficiency between taxa. 2.) Lower avg degree of linkages combined with higher diversity of significant nodes (taxa) indicate a more resilient, less fragile microbial community to external pressures (e.g. less probability of community (and func7onal) collapse). 3.) Biochar module hubs were more likely to be N fixers, chi/n degraders with a high number of linkages 4.) A major no biochar module hub (module 12) was Nitrospira, an ammonia oxidizer, not present in biochar network 5.) Major differences in the number of Acidobacteria, Proteobacteria, and Gemma7monadetes between networks.
Random Matrix Theory-‐based Molecular Ecological Network Analysis was performed based on the significant community differences in the Poamoho Napier biochar / no biochar treatments:
W-‐Napier-‐PHarv
Biochar Composi7on & Crop Yield
Crop Yield tended to increase in the Napier crop with no differences observed in the corn harvest.
Crop Yield Biochar Par/cle Size Distribu/on
72% of biochar par7cles were less than 1 mm diameter.
Flux Data
N2O
CO2
GHG Flux Data. B i o c h a r am e n dme n t t e n d e d t o d e c r e a s e emissions of CO2 and N2O in the mollisol but increase emissions in the oxisol. This soil-‐type dependency on responses is a common trend throughout. Methane consump7on tended to be lower in the b i o c h a r amendmen t , though not significantly.
CH4
Soil Chemical Data
Biochar affects are NOT UNIVERSAL, but dependent on soil type x crop. Crop Effects: • Crop yield tends to increase with Napier but not with corn. GHG Emissions: • Changes in CO2, N2O and CH4 consump7on due to biochar did not significantly differ, trends were due to soil type interac7ons with a trend of less CO2 and N2O produc7on in the mollisol but not in the oxisol. Soil Chemical Data: Carbon tended to be retained in the biochar treatment within the Napier crops more than the no biochar treatment. Percent carbon was always higher in the biochar amendment. Nitrogen also tended to be higher in biochar, though generally not significantly. Microbial Communi/es: • Microbial communi/es changed significantly in most cases with biochar
amendment, though soil type x crop differences exist. • Microbial communi/es were “homogenized” with biochar amendment. • Biochar does not impact overall microbial diversity. • In Poamoho Napier, biochar resulted in a more resilient, less fragile microbial
community with more N fixers and aroma/c hydrocarbon degraders compared to ammonia oxidizers (e.g. N loss) in the no biochar treatment.
Microbial Community Composi7on nMDS of bacterial community structure represen7ng a total of 39.3 million MiSeq reads at 13,300 seqs/sample and 19,721 OTUs.
Mollisol vs. Oxisol (Waimanolo – Poamoho)
Corn vs. Napier Biochar vs. No Biochar Pre-‐Plant vs. Harvest
P-‐Corn-‐PHarv
P-‐Napier-‐PPlant
W-‐Corn-‐PHarv
W-‐Napier-‐PPlant
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Biochar amendment results in: 1. Significantly decreased plot-‐scale heterogeneity -‐ “homogenizes the community” 2. Significant shies in bacterial community composi/on: a. In both corn and napier within the oxisol at Poamoho b. In the corn within the Waimanalo mollisol soil 3. Decreases in # of Acidobacteria and increases in Proteobacteria in Poamoho 4. Larger # of Acidobacteria, Proteobacteria, Crenarchaeota in Waimanalo Differences were best correlated to pH and Mg (BEST, ρ=0.531, p=0.001; ρ=0.35, p=0.01) Time was a significant factor in all plots (e.g. pre-‐plant, harvest @ 1 yr) Soil type was also highly significant (F=77.56, p=0.001).
Biochar does not generally influence diversity measures. Soil type and plant effects shape the community.
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P_PP_NAPIER W_PP_NAPIER W_PH_NAPIER W_PP_CORN P_PH_CORN
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Shannon's Diversity
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Carbon. Pre-‐plant and harvest showed biochar with significantly higher %C, due to addi7on. Corn soils all showed C loss from pre-‐plant to harvest. Napier soils showed C gain in biochar amendment while no biochar showed C loss.
Change in %C
Economic Analysis Flowchart
Nitrogen. %N tended to be higher in biochar treatments, though generally not significantly both at pre-‐plant and harvest two.