Quantifying changes in land management practice and impact on erosion and ground cover in the NSW Mallee 2003-2015

John Leys1, Terry Koen1, Leigh Pyke 2, Craig Strong3
1NSW Office of Environment and Heritage, Gunnedah, NSW, Australia, 2Mallee Catchment Management Authority, Mildura, Victoria, Australia, 3Fenner School Australian National University, Canberra, ACT, Australia

Land management practice has a huge effect on erosion and ground cover. Understanding how land management practices change in space and time is essential to understanding changes in erosion levels in the Mallee (see other papers at this conference).

The Western Region Local Land Services has been undertaking surveys of its district since 2003. 260 geo referenced sites are visited twice a year. The novel method means all observations are done from a car sitting on a public road that is 30 to 150 m from the observation site.

In addition to base data such as geomorphic unit and soil type, the principal attributes repeatedly measured are:

Land management practices that are desirable (Best Managment Practices - BMPs) are scored to see if they are increasing with time.

Over the 13 years of the survey, BMPs have increased from 15 to 72 %. The biggest change has been in the adoption of conservation tillage, predominately the use of chemicals to control weeds in the pre winter crop. Perennial pastures have also increased from less than 10% to 50% on pasture sites. It should be noted that less than 10% of sites were pasture in April 2015.

Ground cover has increased since its first assessment in 2007 when about 55% of sites achieved the ground cover target of > 50% cover. This has steadily increased to 89% of sites in 2015. The major driver of increased cover has been the shift from cultivation to chemical fallow preparation. In the last 5 years, greater than 80% of chemical fallow sites have achieved the cover target. No more than 30% of tilled sites have achieved the target since 2007.

As a consequence of the adoption of BMPs, wind erosion has decreased from 42% of sites in 2003 to 3% in 2015. This improvement is not because of better seasons as 2003 and 2015 both had similar annual rainfall of about 200mm.

These results confirm that farmers are improving their farm practices. As a consequence the sustainability of the soil resource is being improved and farmers are delivering ecosystem services to the community.