New challenges for lucerne in southern Australian farming systems : identifying and breeding diverse lucerne germplasm to match these requirements.
Date
2008
Authors
Humphries, Alan Wayne
Editors
Advisors
Bellotti, Bill
Rathjen, Anthony John
Auricht, G. C.
Rathjen, Anthony John
Auricht, G. C.
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Thesis
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Abstract
Lucerne is a deep-rooted perennial pasture that is promoted to land managers in
southern Australia to mitigate the effects of dryland salinity, a problem of national
significance caused by the replacement of native trees and shrubs with annual crops
and pastures. In recent years, the acceptance of climate change has provided further
rationale for increasing the use of perennial legumes in our farming systems.
Perennial legumes have a role in offsetting C02 emissions by sequestering C and N in
soil, and provide new, resilient options for future farming in a warmer and more
variable climate. This research has focused on evaluating the diverse range of
germplasm found in lucerne (Medicago sativa spp.) for a range of attributes in order
to determine its compatibility with existing and future farming systems in southern
Australia.
Regional field evaluation at 8 sites in southern Australia showed that lucerne is a
broadly adapted and robust plant. After 3 years, plant density ranged from 2-55 plants
/ m2 with differences in persistence attributed to tolerance to a combination of stresses
including soil acidity, saline and sodic subsoils, drought conditions and persistent
heavy grazing. Highly winter-active lucerne (class 9-10) was confirmed to be the
most suitable group for short phase rotations in southern Australia, providing grazing
is well managed. This germplasm was less persistent than other winter activity
groups, but produces more total herbage yield in environments with winter dominant
rainfall patterns. Highly winter-active lucerne has poor persistence under continuous
grazing, but this may aid in its removal when used in rotation with crops. Winteractive
germplasm (class 6-8) was more grazing tolerant and persistent, making it the most suitable group for longer phase rotations (>4 years), or where more flexible
grazing management practices are required (i.e. 35 days grazing followed by 35 days
recovery). Individual grazing tolerant plants from this group were selected and
randomly inter-mated to form new breeder’s lines in the development of a grazing
tolerant cultivar.
For the first time, the high water-use of a farming system involving wheat overcropped
into lucerne is presented. Lucerne over-cropped with wheat used an
additional 43-88 mm of water in comparison to continuous wheat at Roseworthy and
Katanning respectively. Over-cropping reduced wheat yield by 13-63%, but it can be
more efficient in terms of land area to grow lucerne and wheat as a mixture than on
separate parcels of land. Very winter-dormant lucerne (class 1-2) appears to be less
competitive with winter cereal crops during wheat establishment. It may also be
possible to reduce lucerne’s competition with wheat at the critical stage of anthesis,
with low spring yielding lucerne varieties identified in this research (SA37908). This
group of plants provides excellent potential for the development of high water-use
farming systems because they are grazing tolerant and persistent, and have summer
forage production and sub-soil water extraction rates that are equivalent to winter active
lucerne.
The research has been used to identify the perfect ideotype for lucerne in phase
farming and over-cropping systems, which can be used to set targets in future
breeding programs. The research also highlights current opportunities for the
integration of lucerne into southern Australian farming systems to help curb the
spread of dryland salinity and reduce the impact of climate change.
School/Discipline
School of Agriculture, Food and Wine
Dissertation Note
Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008
Provenance
Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.