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Linking Soil Quality to Economic Incentives Ralph C. Martin, Ph.D., P.Ag.
Loblaw Chair, Sustainable Food Production Tel: 519-‐824-‐4120, Ext 52460 Email: [email protected]
Soil Organic Matter (SOM) is good, good, good
SOM is added with green manures, brown manures and crop residues SOM helps to bind soil particles into good soil structure SOM matter allows infiltration SOM provides resilience during droughts, floods and extreme conditions
Soil Carbon A. Nelson (M.Sc. Thesis -‐ U. of M.)
Rotation had largest effect on soil carbon; soil carbon higher in rotations including perennial forages, regardless of organic or conventional management
Ontario 3-‐Year Crop Rotation
www.southernsare.org; www.uoguelph.ca; www. Scientificamerican.com
Winter wheat over-seeded with red clover
Soybean Corn Year One
Year Two Year Three
Red Clover Benefits for Soils
Increases Microbial Activity
Sources: Lupwayi et. al , 1998; Snapp et. al, 2005; Queen et. al, 2009; Blaser et. al, 2011
Increases Aggregate Stability
Improves Water Holding Capacity
Erosion Prevention Increases Soil
Organic Matter
Decreases Soil Compaction
Builds Soil Tilth
Photo: Amélie Gaudin Gaudin
Biological Infrastructure of Agriculture
Well managed forages provide cost effective feed, soil cover, C, nutrients + Grasses for biomass sales, soil cover, C and nutrients + Cover crops are soil builders, soil cover, C and nutrients + Should governments support biological infrastructure?
Wheat Straw and Corn Stalks
If remove crop residues from arable land for bio-‐products and bio-‐fuel, then crucial to maintain SOM with soil builders, with and between cash crops.
Possible Accounting
1) NMP include C balance (inputs removal) to show if SOM is declining or improving?
2) Can SOM be measured cost effectively and accurately enough, every 5 years, on each field?
3) Crop insurance fees might decrease if SOM levels increase, or vice-‐versa
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White Elephant of N
About 48% (and rising) of people depend directly on the Haber-‐Bosch process for basic food Excess N losses to water (NO3) and air (N2O). N fertilizer is one-‐third of global agricultural energy budget and related GHG emissions
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Use N Efficiently -‐ Legumes, cover & catch crops -‐ Recycle manure, MSW, AD digestate and sewage
-‐ Organic Ag -‐ Deen -‐ Maximum Economic N Rate (MERN) for corn starts to level off at 100 kg N/ha and, after clover, at 50 kg N/ha; for next 100 kg N/ha, MERN ranges from $ 0 -‐ $25/ ha
-‐ Calculate MERN for each crop, in NMP. Only N fertilizer, up to lowest range of MERN, eligible as a tax deductible expense?
-‐ Reduce food waste
Soil Renewal Rate To form a 2.5 cm depth of soil (340 t/ha) requires 200 to 1000 years, a renewal rate of 0.3 to 2 t/ha/yr In U.S.A., soil erosion averages 18 t/ha/yr (Pimental et al. 1987. Bioscience 37:277-‐283)
Productivity of eroded soil
Productivity of eroded soils will decline even if fertilizer is added (Brady and Weil 2002, Fig 17.8)
or if the eroded soil is irrigated (Larney et al. 1995 J. Soil Water Conserv. 50:87-‐91)
The Revised Universal Soil Loss Equation (RUSLE) = RKLSCP
R = rainfall erosivity K = soil erodabality LS = length and steepness of slope C = cover and crop management P = practices of erosion control (Brady and Weil 2002, 754 -‐ 763)
Observing and Caring
Erosion control practices tend to increase on farms:
1) with farmers mostly on the farm 2) organized as family units
(Wall et al. 2002)
Attitude of Gratitude Take moments to be thankful, especially for healthy soil and food.
Appreciate what we have and treasure it.
Vision to Sustain Food A food system, based on healthy
soil, clean air and water, minimal waste and regenerative energy, to support profitable and resilient farming and fishing communities and a healthy food supply for all.
