Table 4.4 Effect of agricultural management practices on SOC and consequent agronomic effects. Agronomic consequences Agronomic consequences Soil carbon consequences Soil carbon consequences No Practice d What we know What we don’t know What we know What we don’t know Increase area pasture productivity is reduced enterprise flexibility increased SOC under equilibrium storage of perennial greater in high rainfall if locking in the area of kikuyu = 0.25–0.5t/ha/yr which soil type is SOC pastures areas and for deeper soils perennial pasture on deep sands increased in and where increased soil nutrient do nutrients need to be decreased SOC in duplex C pool is SOC moving into concentrations added or are they captured soils (Esperance) rather than lost to the system is there C leakage with greater stocking rates Claying can reduce under No data addition of 5% clay can can verification be linked to clay some circumstances increase SOC by 2–4t/ha application at equilibrium generally increased which C pool is increased production is an upper clay threshold Biochar variable agronomic where benefits can be variable char qualities char quality effect on SOC benefits assured i.e. low storage can absorb herbicides phosphorous (P) soils in increased soil nutrient long-term effect of herbicide Central Midlands concentrations absorption do these nutrients need to be removal of nutrients in added or are they captured biochar feedstock rather than lost to the system variable char qualities long-term cost and effect on trade-off between energy toil biology and char production Transfer of labile C to protected C pool effect on – productivity char quality effect on crop/pasture productivity
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
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