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Expanded Assessment for Alternative Practices: Environmental Comparison

A Comprehensive Environmental and Economic Assessment Method Applied to the Southwest Michigan Greenhouse Gas Mitigation Cropping Experiment Third USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry March 21-24, Baltimore MD Susan Subak, Ph.D.

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Expanded Assessment for Alternative Practices: Environmental Comparison

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  1. A Comprehensive Environmental and Economic Assessment Method Applied to the Southwest Michigan Greenhouse Gas Mitigation Cropping Experiment Third USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry March 21-24, Baltimore MD Susan Subak, Ph.D. Institute for the Study of Society and Environment

  2. Expanded Assessment for Alternative Practices: • Environmental Comparison • - greenhouse gas emissions • - nitrogen loadings • chemical applications • Question: Do herbicides applied for No-Till represent a significant pollution trade-off for greenhouse gas abatement? • Does the benefit of nitrogen reduction for low-input agriculture surpass greenhouse gas benefits for No-Till? • Economic Comparison • - direct input cost savings • - greenhouse gas reduction value • (value of reducing nitrogen and chemicals not assessed) • - crop value (price x yield)

  3. Kellogg Biological Station Cropping Experiments NSF – LTER; Michigan State University Data logs: 1991-1999 Corn/wheat/soybean rotation T1: Conventional Tillage T2: No-Till T3: Low Input with Legume Cover T4: Organic with Legume Cover Robertson, G.P., Paul, E.A, Harwood, R.R.Greenhouse Gases in Intensive Agriculture: Contributions of Individual Gases to the Radiative Forcing of the Atmosphere. Science 289(5486): 1922-1925.

  4. Greenhouse Gases: From Robertson et al 2000: Soil C CO2 inputs to fertilizer, lime, fuel N2O CH4 Nitrogen Loadings: Compiled from logbooks from KBS for fertilizer applications Toxicity Index: Derived by author based on logbooks from KBS for herbicide and pesticide applications

  5. Toxicity Index: I = a x b x 1/c x d x 1/e a = volume chemical applied (liter/hectare/year) b = % active ingredient c = lethal concentration half life (LC50) for trout (mg/liter) log 10 scaled 1 to 5 d = groundwater ubiquity index (GUS) log 10 scaled 1 to 5 e = water degradation half life (days) log 10 scaled 1 to 5

  6. Value of alternative practices compared with Conventional Tillage: • Input Costs • Greenhouse Gas Emissions Abatement ($10 t CO2e) • Crop Value

  7. Conclusions from KBS Example: Environmental: - Chemical impact (Toxicity Index) of CT, NT and Low Input/legume were similar - Nitrogen loadings were very different for the low-input practices (compared with CT and NT) but importance depends on estimated local impact - Environmental benefit from reduced GHG and/or nitrogen loadings compared with CT is clear Economic: - Higher crop yields from NT were canceled out by higher direct input costs - Lower crop yields from Low-Input/legume were canceled out by lower input costs - Greenhouse gas abatement value is low, under current assumptions, but can change the incremental value from negative to positive when comparing these alternatives to CT

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