Cover crops Non-commodity crops planted in between rows of commodity crops or during fallow periods Increased soil C sequestration Reduced indirect N2O emissions from soils due to a reduction in N leaching Reduced emissions from fertilizer manufacture Improved soil nutrient content Reduced wind and water erosion Reduced fertilizer needs Reduced weed growth Reduced irrigation needs Supplemental livestock feed (extends grazing season, cattle weight gain) Increased profit Requires extra time and knowledge to manage, and some new techniques for growing commodity crops Requires more fuel use for crop planting Conservation tillage A range of cultivation techniques (including minimum till, strip till, designed to minimize soil disturbance for seed placement, by allowing crop residue to remain on soil after planting Increased soil C sequestration Reduced indirect N2O emissions from reduction in run-off Reduced emissions from fertilizer manufacture Improved soil water retention and drainage Reduced water and wind erosion Reduced fertilizer needs Reduced fuel and labor costs from fewer field passes Improved yields Potential increase in herbicide use Increased pest threats in repetitive single commodity production Rotational or mob livestock grazing on pasture Grazing practices that maximize plant health and diversity, while increasing the animal carrying capacity of the land Increased soil C sequestration Reduced CH4 emissions from enteric fermentation (due to improved feed) Increased plant cover and productivity Improved soil water retention and drainage Reduced and wind erosion Increased herd size Can increase length of grazing season Reduced need for purchases of feed Pastures more able to exclude weeds / exotic species Potentially reduced herbicide costs Helps avoid burning fields as a management practice Requires careful management in some areas with sensitive species Anaerobic digester Enclosed system in which organic material such as manure is broken down by microorganisms under anaerobic conditions Reduced N2O and CH4 emissions from manure management Reduced emissions from fertilizer manufacture Reduced risk of accidental toxic leakages (pathogens killed) Reduced ammonia and VOC emissions Processed solids can be used as bedding Reduced need for fertilizers (as nutrient availability in the digestate is increased) Electricity / heat generation Digester technologies can be expensive
Windbreaks Plantations usually made up of one or more rows of trees or shrubs Increased C sequestration in biomass and soils Reduced soil erosion Greater animal survival and health in livestock systems *, A more extensive discussion of the advantages and disadvantages of different management practices can be found in Stockwell & Bitan (2011)
Table 4 Advantages and disadvantages of common performance metrics Metric Advantages Disadvantages GHG flux per unit land area (e.g., flux / ha) Useful to entities that define policies or that manage large amounts of land (e.g., government agencies) Reflective of the overall level of GHG fluxes on farms Fails to consider efficiency of farm production GHG flux per unit product (e.g., flux / tonne beef) Better allows for comparisons within the same industry Better able to represent the effects of mitigation measures that have a relatively small GHG impact, but that nonetheless improve productivity Performance data are frequently sought by buyers on a per-product Calculation may be complicated by the variety of products that come from farms and the different allocation methods used to assign GHG fluxes (see below) Does not consider product value Does not reflect the overall climate impact of farms (which would vary depending on the volume of products produced) GHG flux per unit of farm input (e.g., flux / MJ metabolisable energy intake) Provides an understanding of the effects of feed type and amount on animal systems, or of the efficiency of nutrient use in cropping systems Calculation may be complicated by the need to allocate GHG fluxes GHG flux per unit of quality content in final product (e.g., per unit of fat, protein or metabolisable energy content) Considers a fundamental objective of most agricultural production – to provide food energy Calculation may be complicated by the need to allocate GHG fluxes