Policy into Practice; Statistics the Forgotten Gatekeeper

The Australian Federal Government Carbon Farming Initiative (CFI) was a voluntary carbon offsets scheme. It allowed land managers to earn carbon credits by changing land use or management practices to store carbon. The Carbon Farming Futures (CCF) program ran from 2012 to 2017 to identify where farmers can boost productivity and profitability; improve soil and reduce greenhouse gas emissions. The Action on The Ground program was one component of the CCF which aimed to assist landholders in trialing new technologies and practices. Laboratory and field plot research indicated that ploughing nutrients into the soil with crop residues/stubble increased the amount of soil carbon stored. Our project aimed to test if this was possible using farm equipment. The challenge was to design experiments with plots large enough to be managed with commercial farm machinery that deliver enough precision to test different treatments. We tested carbon sequestration methods in 14 fields in different bioregions. Soil variability was estimated using two electromagnetic surveying instruments. Randomized block experiments were established in fields after areas of similar soil were identified by geostatistics and finite mixture models. The field experiments failed to reproduce the high sequestration rates of the earlier, more controlled, research. We describe one experiment in this chapter and propose reasons for this failure to sequester carbon. The hybrid demonstration/research approach is applicable in many other situations where agricultural policy or practice change are to be tested at farm scale.