Table 4.4 Effect of agricultural management practices on SOC and consequent agronomic effects. No Practice d Agronomic consequences What we know Agronomic consequences What we don’t know Soil carbon consequences What we know Soil carbon consequences What we don’t know Increase area of perennial pastures pasture productivity is greater in high rainfall areas and for deeper soils increased soil nutrient concentrations reduced enterprise flexibility if locking in the area of perennial pasture do nutrients need to be added or are they captured rather than lost to the system is there C leakage with greater stocking rates increased SOC under kikuyu = 0.25–0.5t/ha/yr on deep sands decreased SOC in duplex soils (Esperance) equilibrium storage which soil type is SOC increased in and where C pool is SOC moving into Claying can reduce under some circumstances generally increased production No data addition of 5% clay can increase SOC by 2–4t/ha at equilibrium can verification be linked to clay application which C pool is increased is an upper clay threshold Biochar variable agronomic benefits increased soil nutrient concentrations removal of nutrients in biochar feedstock variable char qualities trade-off between energy and char production where benefits can be assured i.e. low phosphorous (P) soils in Central Midlands do these nutrients need to be added or are they captured rather than lost to the system long-term cost and effect on toil biology Transfer of labile C to protected C pool – effect on productivity char quality effect on crop/pasture productivity variable char qualities can absorb herbicides char quality effect on SOC storage long-term effect of herbicide absorption
4.4 continued - effect of agricultural management practices on SOC and consequent agronomic effects. No Practice d Agronomic consequences What we know Agronomic consequences What we don’t know Soil carbon consequences What we know Soil carbon consequences What we don’t know Rangelands management change is principally manipulation of total grazing pressure quantifiable relationship between grazing management and SOC concentration leakage (displaced grazing) low capacity of soils to store C high verification costs high spatial and temporal heterogeneity legally complex issues surrounding native title and C ownership baseline SOC lack of clarity around lessees’ obligations regarding maintaining rangeland condition — meeting the CF criteria how to monitor SOC between baseline and subsequent verification assessments Minimum tillage generally improved and profitability reduced erosion risk No data won’t increase SOC rate of SOC decline less than with conventional tillage No data Revegetation and reforestation agricultural production displaced retaining harvest residues (slash) will increase soil C levels retaining slash will help retain other soil nutrients reduced soil erosion leakage/reduced emissions (altered agricultural intensity on non-forest land) higher operational costs associated with slash retention possible increased fire risk from retaining slash decrease in SOC following plantation establishment best chance of increasing SOC in high rainfall zone increase in SOC with harvest if the (residues) left on site little change in SOC deeper than 10cm may be decades before net increase in SOC No data
Table 4.4 continued - effect of agricultural management practices on SOC and consequent agronomic effects. No Practice d Agronomic consequences What we know Agronomic consequences What we don’t know Soil carbon consequences What we know Soil carbon consequences What we don’t know Preventing soil erosion erosion control most likely to be driven by associated productivity benefits erosion associated with large productivity losses No data erosion associated with large SOC losses No data Stubble retention reduced soil erosion water conservation soil C consequences No data should increase SOC No data Increased production (fertiliser, disease and pest management) potentially increased profitability No data should increase SOC potential GHG emissions from increased fertiliser No data Addition of offsite organic matter (compost, manure) can reduce nutrient requirements can increase plant productivity No data should increase SOC No data Reduce fallows (green manure/cover crop) loss of income in year green manure grown water conservation weed control can reduce nutrient requirements No data increase plant inputs compared to bare fallow No data Sources: soil carbon workshop 2012; Sanderman et al. (2010); CSIRO Land and Water; Paterson and Hoyle (2011).
Table 4.7 Carbon sequestration rates and time to equilibrium for soil, biomass and whole landscape in mulga woodland in Queensland (measured) and rates for various landforms in WA (estimated). State/Region Vegetation/land system Management intervention Soil tCO2-e/ha/yr Biomass tCO2-e/ha/yr Total tCO2-e/ha/yr Time period yr Qld* Mulga Destocking 0.18 0.73 – 0.9 0.92 – 1.1 25 WA** Average over all rangelands Destocking and fire management No data No data 0.15 – 0.62 20 Pilbara Various landforms Destocking 0.05 -0.06 -0.01 30 Pilbara Various landforms Intensification 0.04 0 0.04 30 Kimberley Various landforms Destocking -0.04 – 0.01 0.12 – 0.51 0.13 – 0.47 30 Kimberley Various landforms Intensification -0.02 – 0.21 0.08 – 1.66 0.06 – 1.88 30 Kimberley Various landforms Destocking and fire management 0.19 – 0.25 1.98 – 2.29 2.17 – 2.55 30 Note: Negative values indicate a net release of carbon. Sources: * Witt et al. 2011; ** Harper et al. 2007; *** Alchin et al. 2010.
Table 6.1 Total sequestration (Seq.) and mean annual value of carbon offsets generated from sequestration activities over the period from establishment until storage equilibrium (Equil.) is reached ($/ha/yr). Offset values have been adjusted for withholding a 5% risk-of-reversal buffer from sale. No Activity data Estimated capital ($/ha) & maintenance costs ($/ha/yr) Rainfall mma Equil. yra no Seq. Value of carbon offsets $10/ha/yr /tCO2-e of carbon offsets $15/ha/yr /tCO2-e Value of carbon offsets $25/ha/yr /tCO2-e Value of carbon offsets $35/ha/yr /tCO2-e Value of carbon offsets $45/ha/yr /tCO2-e Reforestation – mixed species1 400–1000 establishment by direct seeding, 2000 seedling establishment 300 30 56–209 18–66 27–99 44–65 62–232 80–298 Reforestation – mixed species1 400–1000 establishment by direct seeding, 2000 seedling establishment 450 30 85–425 27–134 40–202 67–336 94–471 121–606 Reforestation – single species2,3 1250 establishment 25 maintenance <350 41 566 131 197 328 459 590 Reforestation – single species 2,3 1250 establishment $25 maintenance >550 41 894 207 311 518 725 932 Reforestation – mixed species2,3 2000 establishment 25 maintenance <350 41 348 81 121 202 282 363 Reforestation – mixed species2,3 2000 establishment 25 maintenance >550 41 787 183 274 456 638 821 Table .1 continued - total sequestration (Seq.) and mean annual value of carbon offsets generated from sequestration activities over the period from establishment until storage equilibrium (Equil.) is reached ($/ha/yr). Offset values have been
adjusted for withholding a 5% risk-of-reversal buffer from sale. No Activity data Estimated capital ($/ha) & maintenance costs ($/ha/yr) Rainfall mma Equil. yra no Seq. Value of carbon offsets $10/ha/yr /tCO2-e of carbon offsets $15/ha/yr /tCO2-e of carbon offsets $25/ha/yr /tCO2-e Value of carbon offsets $35/ha/yr /tCO2-e Value of carbon offsets $45/ha/yr /tCO2-e Increased soil C4,5 Move from cropping to perennial pasture Cost of pasture establishment and management part of livestock system 40 22 5 8 13 18 24 Increased soil C4,5 Move from continuous to ley cropping Cost of pasture establishment and management part of livestock system 40 37 9 13 21 30 30 Increased soil C4,5 Move from ley cropping to perennial pasture Cost of pasture establishment and management part of livestock system 40 120 28 42 70 97 125 Increased soil C6 Addition of compost at 30 & 60m3/ha Cost of compost offset by reduced fertiliser and increased productivity No data 7 4 6 9 15 21 27 Table .1 Continued - total sequestration (Seq.) and mean annual value of carbon offsets generated from sequestration activities over the period from establishment until storage equilibrium (Equil.) is reached ($/ha/yr). Offset values have been
adjusted for withholding a 5% risk-of-reversal buffer from sale. No Activity data Estimated capital ($/ha) & maintenance costs ($/ha/yr) Rainfall mma yra no Seq. Value of carbon offsets $10/ha/yr /tCO2-e Value of carbon offsets $15/ha/yr /tCO2-e Value of carbon offsets $25/ha/yr /tCO2-e Value of carbon offsets $35/ha/yr /tCO2-e Value of carbon offsets $45/ha/yr /tCO2-e Increased soil C6 Addition of compost at 30 & 60m3/ha Cost of compost offset by reduced fertiliser and increased productivity No data 7 7 10 15 24 34 43 Restoration of rangelands7,8 Opportunity cost of destocking Management/fencing cost of intensification No data 30 3 (range is 0-56) 1 1 2 3 4 Restoration of rangelands7,8 Opportunity cost of destocking Management/fencing cost of intensification No data 30 15 is 0-56) 5 7 12 17 21 Restoration of rangelands7,8 Opportunity cost of destocking Management/fencing cost of intensification No data 30 30 (range is 0-56) 9 14 24 33 43 Savanna fire management and reduced stocking9,10 $0.44/ha/yr foregone income from destocking by 50%, $0.06/ha/yr fire management >1000 50 26 5 7 12 17 22 .1 footnotes - total sequestration (Seq.) and mean annual value of carbon offsets generated from sequestration
activities over the period from establishment until storage equilibrium (Equil.) is reached ($/ha/yr). Offset values have been adjusted for withholding a 5% risk-of-reversal buffer from sale. Alb. = Albany; Esp. = Esperance. Note: values for compost are over seven years as it is unclear when equilibrium is reached. Values for rangeland restoration are based on modelled estimates of sequestration which were highly variable according to location and landform. Sources: 1 FullCAM modelling; 2 Polglase et al. (2008); 3 Crossman et al. (2011); 4 Carson (2012); 5 Soilquality.org.au (2012); 6 Paulin & O’Malley (2008); 7 Harper et al. (2007); 8 Alchin et al. (2010); 9 Douglass et al. (2011); 10 Richards et al. (2011). 6.2 Mean annual value of carbon offsets generated from emission avoidance activities. No Activity data no Estimated capital and operating costs no Avoided emissions tCO2-e/yr Value of carbon offsets $10/ha/yr /tCO2-e of carbon offsets $15/ha/yr /tCO2-e Value of carbon offsets $25/ha/yr /tCO2-e of carbon offsets $35/ha/yr /tCO2-e of carbon offsets $45/ha/yr /tCO2-e Agricultural soils (reduced N2O emissions, assume 10% reduction in emissions) 1,2 Cost of urease inhibitors, nitrification inhibitors and modified crop agronomy 0.006/ha (dryland crops) 0.7 0.1 0.2 0.2 0.3 Agricultural (reduced N2O emissions, assume 10% reduction in emissions) 1,2 Cost of urease inhibitors, nitrification inhibitors and modified crop agronomy 0.133/ha (irrigated crops) 1.2 2 3 5 6 Manure management (biogas from waste pond, DAFWA Medina) 3,4 $191 000 (pond construction) variable operating 270 per pond 2700 4050 6750 9450 12 150 Enteric fermentation (reduced CH4 emissions) 5,6 Variable costs of special breeding and genetic modification 0.53 per cow 5 8 13 19 24
Enteric fermentation (reduced CH4 emissions) 5,6 Variable costs of special breeding and genetic modification 0.019 per sheep 0.2 0.3 0.5 0.7 0.9 Enteric fermentation (reduced CH4 emissions) 5,6 Variable costs of feed additives 0.41 per cow 4 6 10 14 18 Table .2 continued - mean annual value of carbon offsets generated from emission avoidance activities. No Activity data no Estimated capital and operating costs no Avoided emissions tCO2-e/yr Value of carbon offsets $10/ha/yr /tCO2-e of carbon offsets $15/ha/yr /tCO2-e of carbon offsets $25/ha/yr /tCO2-e Value of carbon offsets $35/ha/yr /tCO2-e Value of carbon offsets $45/ha/yr /tCO2-e Enteric fermentation (reduced CH4 emissions) 5,6 Variable costs of feed additives 0.002 per sheep 0 0 0 0 0 Enteric fermentation (reduced CH4 emissions) 5,6 Variable of pasture management 0.46 per cow 5 7 12 16 21