Soil carbon and farming systems Faculty of Agriculture dal.ca Soil carbon and farming systems D. Lynch Jan. 23rd 2018

Climate Change and Soil Carbon Paris Agreement. Target of Net Zero GHG by 2050 – requires emissions reduction of 8-10% per year. But energy improvements only ~4% reduction per year. Soil C sequestration - Potential to reduce 3-15% of emissions. Global Soil Organic C map. Released by FAO on World Soil day, Dec. 5th 2017. French initiative of 4/1000. An annual increase of 0.4% in soil C globally would halt the increase in atmospheric CO2. (www.4p1000.org) Explain soil organic matter is about 50% C. Soils constitute the largest terrestrial organic C pool (~1,500 Pg C to a depth of 1 m; 2,400 Pg C to 2 m depth11), which is three times the amount of CO2 currently in the atmosphere (~830 Pg C) and 240 times the current annual fossil fuel emissions (~10 Pg)9. Thus, increasing net soil C storage by even a few per cent represents a substantial C sink potential. Paris Agreement – 50% reduction in GHG by 2030 2 M kg (2,000 t) per 0-15cm/ha. If 1% C = 20 t C/ha.

Diverse cropping systems Mixed farming Manuring and NM Agroforestry Conservation tillage Cover crops Diverse cropping systems Mixed farming Manuring and NM Agroforestry Note practices-could add intercrops and especially permanent soil cover as important also apsects of ‘conservation agriculture; climate-smart agriculture; carbon farming etc. Ideally gains of as much as 1 t of C per ha per year can be measured with some of these practices. Paris Agreement – 50% reduction in GHG by 2030 Lal, Science, 2004

Soil C status Net effect of management on soil C most important. Influenced by: Rate of return of C (residues) Mineralization (tillage) of C Soil C storage capacity (texture) Depth in soil

Agricultural Intensification and Soil C Eastern Canada - Increasing shift to more annual cropping, and low residue crops, estimated to be depleting soil organic C levels (AAFC; OMAFRA). OMAFRA 2016 PEI– Under intensive potato systems return of residues, even with three year rotation, is below that required to maintain soil C levels. PEI - SOM declining at 0.05% per year AAFC Soil OM iIndictor E. Canada generally large decease, of <90 kg/ha/yr. (agrees with PEI calc. of 0.05% per year) NS data -Agrienvironmental report – on Relative SOC. 0.58. Plus rate of decrease in SOC of 0.68 kg C/ha attributed to? Nyiraneza et al 2017

AGGP project (2016-2021) Goal: To asses the cropping systems of NS and PEI for soil health, soil C storage capacity and soil N supply Soil C and Active C- influence of management intensity, soil type, soil depth, and relationship to soil health. Soil C and Active C- influence of management intensity, soil type, soil depth, and relationship to soil health.

Data Collection – Nova Scotia 2016 Fields Sampled: We sampled 82 farm fields (with 4 samples for most) and 64 research plots for a total of 344 soil samples 2016: Total 82 Vegetable 34 Small Fruit 31 Field Crops 9 Forage 5 Pasture 2017: Total 62 Field Crop 23 Forage 15 Pasture 13 Lowbush Blueberry 5 Vineyard 4 3Vegetable 2 2017 Fields Sampled: We sampled 62 farm fields (with 4 samples each) and 44 research plots for a total of 292 soil samples.

Measuring ‘Active’ Organic Matter Concept of indicator pools. Could include SMB-which in previous studies we found was best indicator. POX-C POM-C Respired-C

Organic Matter level distribution PEI and NS (% of sites) SOM PEI NS <2% 2.0 26.0 2-3 73.0 37.0 3-4 24.0 18.0 >4 0.8 18.0 2016 data only. (using *1.72 conv.) PEI data * Data from Nyiraneza et al 2017 CSSS

Organic Matter level distribution Both the active (recent, partially decomposed) fraction and the silt+plus clay associated OM was highesst under forage and pasture soils. OM: Total 3 Vegetable 2.3 Small Fruit 2.8 Field Crops 3.5 Forage 4.7 Pasture 4.5 POM%: Total 28 Vegetable 25 Small Fruit 28 Field Crops 24 Forage 39 Pasture 40

Total and active SOM pattern was reflected in three key indicators of soil health Agg Stability: Total 48 Vegetable 40 Small Fruit 54 Field Crops 44 Forage 67 Pasture 62 N Flush Total 42 Vegetable 36 Small Fruit 26 Field Crops 59 Forage 92 Pasture 112 WHC: Total 11 Vegetable 12 Small Fruit 12 Field Crops 13 Forage 15 Pasture 17 WHC Does not prevent water from draining in wet periods but can hold on to water to release to crops in dry periods

Relationship SOC to Silt plus Clay Content SOC g/kg Silt+clay content (%)

As SOC increases active C & soil health increases Active C (POM / SOC %) SOC (g C/kg) Cresp. mg/g Active C (POM /SOC %)

Atlantic Soil Health Lab Work in Progress We have completed year 1 of a 5 year program. Samples collected in 2017 are currently being analyzed in the lab. We are working to link soil C and soil health trends to field history. Project is linked to other projects such as CFGA project on development of a C offset protocol for improved pasture management. Atlantic Soil Health Lab Blog: https://atlanticsoilhealth.blogspot.ca Email: SoilHealthLab@dal.ca Twitter: @SoilsLab

Acknowledgements Agriculture and Agri-Food Canada Faculty of Agriculture dal.ca Acknowledgements Agriculture and Agri-Food Canada Natural Sciences and Engineering Research Council Perennia