Climate change factors influencing microbial turnover of soil organic matter Bobbi Helgason Ph.D., P.Ag. Soil Microbiologist, AAFC Saskatoon CCC Compost Matters in Saskatchewan March 15, 2018
Hans Jenny Pedologist (1899-1992) FAO 2015
What is soil health? soil health soil quality http://indianapublicmedia.org/ the continued capacity of a soil to function as a vital living ecosystem that sustains plants, animals and humans USDA, 2016
What is soil health? soil health soil quality http://indianapublicmedia.org/ Soil health. Healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect and weed pests, form beneficial symbiotic associations with plant roots; recycle essential plant nutrients; improve soil structure with positive repercussions for soil water and nutrient holding capacity, and ultimately improve crop production" (FAO, 2008)
Soil Organic Matter is vital for healthy soils! C inputs C losses e.g. CO 2 Soil organic C Soils store carbon and combat atmospheric CO 2 emissions https://www.quartoknows.com/blog/quartohomes/2015/04/22/susta inable-gardens-and-organic-matter/
Soil organic matter and soil life air water mineral stable readily decomposed living biomass yeast, etc. fauna bacteria actinomycetes fungi Soil Organic matter Microorganisms ODE TO ROT Let there be rot, and hence bacteria and fungi sprang into existence to dissolve the knot of carbohydrates photosynthesis achieves in plants, in living plants Dead matter else would hold the elements in thrall-- nitrogen, phosphorus... J. Updike 1985
Climate change???
One scenario of predicted temperature change (Prairie Climate Centre, 2017)
One scenario of predicted precipitation change (Prairie Climate Centre, 2017)
Climate change effects on soil microbes Abundance Composition Activity Balser et al. 2010. How will climate change impact soil microbial communities? In Dixon and Tilston. Soil Microbiology and Sustainable Crop Production doi: 10.10047/978-90-481-9479-7_10
Decomposed crop residue = SOM 3500 km
Barley grown in a chamber with a tracer ( 13 CO 2 ) Harvested, chopped Mixed with soil in the field microcosms 10 atom% 13 C Sampled after 6mo, 1, 2, 3, 5 years How much of the tracer is left? tells us how much of the straw C remains in the soil
Measured decomposition Less residue remained: in sandy soil in warmer, wetter climates How do we predict decomposition?
Predicted decomposition Temperature ( thermal time ) decomposition was similar across sites once temperature effects were accounted for
Climate change predictions Time to 50% decomposition (labile carbon): 1-4 months less Time to 90% decomposition (stable carbon): 1 year faster @cool sites 2 years faster @ warm sites
(Lethbridge vs. Ottawa) Residues are: a. incorporated (0-10cm) b. surface applied (unlabelled residues every fall) mixed residue surface applied residue
Residue remaining in mixed vs. surface applied 24 months after residue addition Ottawa has a warmer, wetter climate residue decomposes faster decomposition is less affected by incorporation
Does this affect the type of SOM created during decomposition? Microbial community structure at 24 months Ottawa Lethbridge Different microbes are active in NT vs. CT, esp. at dry sites.
34-53% C lost during composting 6.5-9% lost after land application Helgason et al. 2006. Estimating C retention in soils amended with composted beef cattle manure. Can. J. Soil Science 85:39-46.
Soil Organic Matter is vital for healthy soils! C inputs C losses e.g. CO 2 Soil organic C Soils store carbon and combat atmospheric CO 2 emissions https://www.quartoknows.com/blog/quartohomes/2015/04/22/ sustainable-gardens-and-organic-matter/
Climate change effects on soil microbes Abundance Composition Activity Balser et al. 2010. How will climate change impact soil microbial communities? In Dixon and Tilston. Soil Microbiology and Sustainable Crop Production doi: 10.10047/978-90-481-9479-7_10
Thank you! Dr. Bobbi Helgason Soil Microbiologist AAFC Saskatoon bobbi.helgason@agr.gc.ca CCC Compost Matters in Saskatchewan March 15, 2018